What is the Automatic Transmission Issues issue on the Porsche 928?

Most 928s were sold with automatic transmissions (Mercedes 4-speed or later Aisin-Warner 4-speed). These transmissions are generally robust but require proper maintenance and develop problems with age. Symptoms include: Harsh shifting, slipping, delayed engagement, no movement in gear, fluid leaks, overheating warning. Typical repair cost: DIY $100-200, Shop $300-2000+.

What is the Cooling System Failures issue on the Porsche 928?

The 928's V8 produces significant heat and relies on a complex cooling system. The water pump, driven by the timing belt, is a common failure point. The radiator's plastic end tanks crack with age. Symptoms include: Overheating, coolant leaks, white smoke from tailpipe, heater not working, temperature gauge fluctuation. Typical repair cost: DIY $300-600, Shop $800-1500.

What is the Vacuum System Deterioration issue on the Porsche 928?

The 928 uses vacuum to power many systems including HVAC controls, door locks, cruise control, and brake booster. Over 25-45 years, the vacuum hoses become brittle and crack, causing leaks. Symptoms include: Climate control not working, doors won't lock, cruise control failure, rough idle, brake booster issues. Typical repair cost: DIY $100-300, Shop $300-700.

What is the Pop-Up Headlight Failure issue on the Porsche 928?

The 928's distinctive pop-up headlights are operated by electric motors driving cables and linkages. The motors can fail, the cables can break or stretch, and the plastic linkage components can crack. Symptoms include: Headlights stuck up or down, slow headlight operation, one headlight won't open, motor noise but no movement. Typical repair cost: DIY $50-200, Shop $200-500.

Porsche 928 Resources - ZRG Classics

Buyer's Guide

What to know before purchasing a 928

Overview

The Porsche 928 (1978-1995) was Porsche's ambitious grand touring car, designed to replace the 911 (it didn't). With its front-mounted V8, rear transaxle, and sophisticated rear suspension, the 928 offered continent-crushing performance and luxury. The water-cooled aluminum V8 grew from 4.5L to 5.4L over production, eventually producing 345 hp in the final GTS. The 928 is a complex, sophisticated machine that rewards knowledgeable owners but can punish those who neglect maintenance. Prices have risen significantly as enthusiasts recognize the 928's unique character.

Quick Facts

Production 1978-1995

Total Produced ~61,000 worldwide

Price Range $15,000 - $150,000+

Best Years 1990-1995 GTS (most powerful, best refined)

Model Variants

928 / 928S

1978-1986

Early cars with 4.5L (219 hp) or 4.7L (288 hp) V8. Good cars but less refined than later models.

Desirability: Low

928 S4

1987-1991

The first major update with 5.0L V8 producing 316 hp. Improved interior and technology. The sweet spot for value.

Desirability: High

928 GT

1989-1991

Sport-oriented model with manual transmission standard, sport suspension, and 326 hp. Rarer than S4.

Desirability: High

928 GTS

1992-1995

The ultimate 928 with 5.4L V8 producing 345 hp, widebody styling, and all the refinements. The most valuable 928.

Desirability: High

Pre-Purchase Inspection Checklist

Critical areas to examine before purchasing. Bring this checklist when viewing a 928.

Engine (Critical)

Timing Belt Service The 928 V8 uses a timing belt that must be replaced every 60,000 miles. Belt failure destroys the engine. If bad: $2,500-4,000 for service / Engine if it breaks
Water Pump Should be replaced with timing belt service. 928 water pumps are expensive. If bad: $600-1,000 for pump alone
Oil Leaks Check cam covers, timing cover, rear main seal, and oil cooler lines. V8 has many potential leak points. If bad: $500-2,000 depending on location
Coolant Crossover Pipes Coolant pipes under the intake manifold corrode and leak. Common failure point. If bad: $800-1,500
Head Gaskets Not common failures but serious when they occur. Check for coolant in oil. If bad: $3,000-6,000

Transmission & Drivetrain

Automatic Transmission Most 928s are automatic. Check for smooth shifting and proper fluid condition. If bad: $3,000-6,000 for rebuild
Manual Transmission (GT) GT and some GTS models have 5-speed manual. Test all gears for smooth engagement. If bad: $2,000-4,000
Torque Tube The tube connecting engine to transaxle contains the driveshaft. Check for vibration. If bad: $1,000-2,500
CV Joints / Axles Rear CV joints wear over time. Listen for clicking in turns. If bad: $500-1,000

Suspension & Steering

Weissach Rear Suspension The 928's sophisticated rear suspension has many bushings and links that wear. If bad: $1,000-2,500 for full rebuild
Power Steering System Check for leaks from pump, rack, and lines. The system operates at high pressure. If bad: $500-1,500
Front Control Arms Bushings and ball joints wear causing poor handling and tire wear. If bad: $600-1,200

Electrical & Systems

Vacuum System The 928 uses vacuum for HVAC, door locks, and cruise control. Leaks cause multiple failures. If bad: $300-800
Climate Control HVAC system is complex with vacuum and electrical components. Test all functions. If bad: $500-2,000
Instrument Cluster Check for working gauges and proper speedometer/tachometer operation. If bad: $400-1,000
Power Seat Motors Electric seats can fail. Test all adjustments including memory function. If bad: $300-800

Body & Interior

Rust Check rocker panels, door bottoms, and around sunroof if equipped. Later cars rust less. If bad: $1,000-5,000+
Leather Condition Interior leather can crack and wear. Check seats, door panels, and dashboard. If bad: $1,000-4,000
Headlight Covers Pop-up headlight covers can crack or discolor. Check operation and condition. If bad: $500-1,500

Pricing Guide

Prices as of 2026. Values vary by location, options, and market conditions.

Project Car

$8,000 - $20,000

Non-running or cars with unknown timing belt history. 928 projects can become money pits.

Driver Quality

$20,000 - $45,000

Running and driving S4 or GT examples with some needs. Budget for maintenance.

Excellent

$45,000 - $80,000

Well-maintained GTS or pristine S4/GT with full service documentation.

Concours / Collector

$80,000 - $175,000+

Low-mileage GTS manual or exceptional early cars. Prices continue rising.

Red Flags - Walk Away If...

Unknown timing belt service history - budget for immediate replacement
Overheating issues or evidence of head gasket failure
Non-functional vacuum systems (door locks, HVAC not working)
Automatic transmission slipping or harsh shifting
Severe oil leaks from multiple locations
Rodent damage to wiring (biodegradable wire coating)
Cars that have sat for extended periods without maintenance

What to Look For

Desirable features and options that add value:

Documented timing belt service within last 60,000 miles
GTS for ultimate performance and value retention
Manual transmission (rare but most desirable)
Service records from Porsche specialists
Working air conditioning and climate control
Complete vacuum system operation
Rust-free body panels
Factory tool kit and books

Ownership Costs

Insurance $800-1,500/year (classic car insurance available)

Annual Maintenance $2,000-4,000 for regular service

Common Repairs $1,000-3,000/year typical

Fuel Economy 16-22 MPG

Expert Tips

The 928 is not a cheap car to own - budget accordingly for proper maintenance
Timing belt service is critical - never skip or delay this maintenance
The S4 offers the best balance of performance and value
GTS prices have risen dramatically - they are genuine collectibles now
Manual transmission cars are extremely rare and command significant premiums
Find a Porsche specialist or independent shop that knows 928s well
Join the 928 Owners Club for excellent technical resources and community support
Parts availability is good but prices are higher than 944
A well-maintained 928 is one of the most capable GT cars ever made
These cars were over-engineered and can exceed 300,000 miles with proper care

Common Issues

Known problems, symptoms, and solutions for the 928 platform

Timing Belt Failure

Advanced

Symptoms: Engine won't start, catastrophic engine noise, bent valves, visible belt damage through inspection hole

The 928's V8 engine is an interference engine that uses a timing belt to drive the camshafts. Belt failure results in piston-to-valve contact and catastrophic engine damage. The 928 has a single belt that drives both camshafts via a complex path around multiple rollers.

Estimated Repair Costs

DIY $300-600

Shop $1500-3000

V8 timing belt service is major job. Replace all rollers.

Common Fixes

Replace timing belt every 30,000-40,000 miles or 4 years
Replace ALL timing belt rollers and tensioner
Replace water pump at the same time
Replace front camshaft and crankshaft seals
Inspect and replace belt cover gaskets
Use only high-quality OEM or premium belts
Budget 8-12 hours labor at a specialist shop

Common Parts

Part	Part Number	Est. Price
Timing Belt	92810515102	$80-150
Roller Set	Various	$200-400
Water Pump	92810603204	$150-250
Tensioner	92810524006	$100-200

Sources: Rennlist, 928 Specialists

Cam Tower Gasket and Oil Leaks

Advanced

Symptoms: Oil leaks at top of engine, burning oil smell, oil on exhaust manifolds, low oil level, smoke from engine bay

The 928 V8 is notorious for oil leaks, primarily from the cam tower (cam cover) gaskets. These gaskets are located at the top of each cylinder bank and seal the camshaft area. They harden with age and heat, causing oil to leak onto the exhaust manifolds.

Estimated Repair Costs

DIY $200-400

Shop $600-1200

V8 leaks from everywhere eventually. Budget for full reseal.

Common Fixes

Replace cam tower gaskets with updated Porsche gaskets
Replace valve cover gaskets at the same time
Inspect and replace cylinder head gaskets if leaking
Replace rear main seal if leaking (requires transmission removal)
Replace oil pan gasket if leaking
Replace all oil cooler lines and seals

Common Parts

Part	Part Number	Est. Price
Cam Tower Gasket Set	92810519503	$80-150
Valve Cover Gasket Set	92810593300	$50-100

Sources: Rennlist, 928 International

Engine Wiring Harness Deterioration

Moderate

Symptoms: Random misfires, check engine light, running issues, no-start conditions, sensors not reading correctly

The 928's engine wiring harness is routed through a hot area near the engine and uses insulation that becomes brittle and cracks with age and heat. This is especially problematic on S4 and later models with more complex engine management.

Estimated Repair Costs

DIY $200-800

Shop $1000-3000

Harness deteriorates with heat. Rebuilt harnesses available.

Common Fixes

Inspect harness for cracked or brittle insulation
Rewrap harness with proper heat-resistant tape or conduit
Repair individual broken wires with proper soldering
Replace entire engine wiring harness (rebuilt available)
Add heat shielding to protect new harness
Clean and protect all electrical connectors

Common Parts

Part	Part Number	Est. Price
Engine Harness (Rebuilt)	Various specialists	$500-1500
Harness Repair Kit	Various	$50-150

Sources: 928 Specialists, Rennlist

Automatic Transmission Issues

Advanced

Symptoms: Harsh shifting, slipping, delayed engagement, no movement in gear, fluid leaks, overheating warning

Most 928s were sold with automatic transmissions (Mercedes 4-speed or later Aisin-Warner 4-speed). These transmissions are generally robust but require proper maintenance and develop problems with age.

Estimated Repair Costs

DIY $100-200

Shop $300-2000+

Fluid and filter service DIY. Rebuild is shop job.

Common Fixes

Regular fluid and filter changes (every 30,000 miles)
Flush transmission cooler and lines
Replace transmission cooler if clogged or leaking
Rebuild or replace valve body for shift quality issues
Replace torque converter if shuddering
Full transmission rebuild for severe issues

Common Parts

Part	Part Number	Est. Price
Trans Fluid (8L)	Dexron VI	$60-100
Trans Filter	92832590100	$30-60

Sources: Rennlist, 928 International

Cooling System Failures

Advanced

Symptoms: Overheating, coolant leaks, white smoke from tailpipe, heater not working, temperature gauge fluctuation

The 928's V8 produces significant heat and relies on a complex cooling system. The water pump, driven by the timing belt, is a common failure point. The radiator's plastic end tanks crack with age.

Estimated Repair Costs

DIY $300-600

Shop $800-1500

V8 runs hot. Full system service important.

Common Fixes

Replace water pump with every timing belt service
Replace thermostat with OEM temperature rating
Replace radiator if plastic tanks cracking or leaking
Replace all coolant hoses (including heater hoses)
Flush cooling system and use proper coolant
Check and clean electric cooling fan operation

Common Parts

Part	Part Number	Est. Price
Water Pump	92810603204	$150-250
Thermostat	92810612701	$40-80
Radiator	Various	$300-600

Sources: Pelican Parts, Rennlist

Vacuum System Deterioration

Easy

Symptoms: Climate control not working, doors won't lock, cruise control failure, rough idle, brake booster issues

The 928 uses vacuum to power many systems including HVAC controls, door locks, cruise control, and brake booster. Over 25-45 years, the vacuum hoses become brittle and crack, causing leaks.

Estimated Repair Costs

DIY $100-300

Shop $300-700

928 uses vacuum for HVAC, locks, cruise. Lines crack with age.

Common Fixes

Replace all vacuum hoses throughout the car
Check and replace vacuum reservoir if cracked
Replace vacuum check valves
Test vacuum actuators in doors and HVAC system
Replace brake booster check valve if brakes feel hard

Common Parts

Part	Part Number	Est. Price
Vacuum Hose Kit	Various	$80-200
Vacuum Reservoir	92857112101	$50-100

Sources: 928 Specialists, Rennlist

Weissach Axle Suspension Wear (S4/GTS)

Advanced

Symptoms: Rear-end wander, unpredictable handling at limit, clunking from rear, uneven rear tire wear

Later 928 models (S4, GT, GTS) use the Weissach rear axle, a sophisticated multi-link suspension that provides passive rear-wheel steering for improved handling. The system uses multiple bushings and control arms that wear over time.

Estimated Repair Costs

DIY $300-600

Shop $800-1500

S4/GTS Weissach suspension. Multiple bushings and links.

Common Fixes

Inspect all Weissach axle bushings for wear
Replace control arm bushings (polyurethane or OEM rubber)
Replace toe links and trailing arm bushings
Check wheel bearings for play
Rebuild or replace control arms if ball joints worn
Perform full rear alignment after suspension work

Common Parts

Part	Part Number	Est. Price
Weissach Bushing Kit	Various	$150-300
Toe Link	92833104700	$80-150

Sources: 928 International, Rennlist

Pop-Up Headlight Failure

Moderate

Symptoms: Headlights stuck up or down, slow headlight operation, one headlight won't open, motor noise but no movement

The 928's distinctive pop-up headlights are operated by electric motors driving cables and linkages. The motors can fail, the cables can break or stretch, and the plastic linkage components can crack.

Estimated Repair Costs

DIY $50-200

Shop $200-500

Motors, cables, and linkages wear. Lubrication helps.

Common Fixes

Lubricate headlight pivot points with white lithium grease
Replace headlight cables if stretched or frayed
Replace headlight motor if failed
Replace plastic linkage components if cracked
Adjust limit switches for proper open/close positions

Common Parts

Part	Part Number	Est. Price
Headlight Motor	92863110100	$150-300
Headlight Cable	92863120300	$40-80

Sources: Rennlist, Pelican Parts

Instrument Cluster and Electronics

Easy

Symptoms: Dead or flickering gauges, inaccurate readings, warning lights stuck on, odometer failure, dim display

The 928's instrument cluster is a complex electronic unit with multiple displays and warning systems. The circuit board develops solder cracks from thermal cycling. Capacitors fail with age. The LCD displays can fade or fail.

Estimated Repair Costs

DIY $100-300

Shop $300-700

Solder cracks and LCD failures. Rebuild services available.

Common Fixes

Re-solder cracked connections on cluster circuit board
Replace failed capacitors
Replace LCD displays with new or NOS units
Replace odometer gears (brass upgrade kits available)
Have cluster professionally rebuilt by 928 specialist

Common Parts

Part	Part Number	Est. Price
Cluster Rebuild Service	N/A	$200-500
Odometer Gear Kit	Various	$20-50

Sources: 928 Specialists, Rennlist

Air Conditioning System Failures

Moderate

Symptoms: No cold air, weak airflow, hot on one side and cold on the other, clicking from dashboard, refrigerant leaks

The 928's automatic climate control system was advanced for its time but is now 25-45 years old. The compressor, condenser, and evaporator all wear out. The early R12 systems have been converted to R134a, often improperly.

Estimated Repair Costs

DIY $200-500

Shop $600-1500

R12 to R134a conversion common. Compressor failures.

Common Fixes

Properly convert R12 systems to R134a
Replace compressor if failed or worn
Replace condenser and receiver/drier if system was open
Repair or replace evaporator if leaking
Replace blend door servo motors
Check vacuum supply to HVAC system

Common Parts

Part	Part Number	Est. Price
AC Compressor	Various	$300-600
R134a Conversion Kit	Various	$100-200

Sources: Rennlist, 928 International

Restoration Guides

Comprehensive guides for rebuilding and restoring your 928

Complete Suspension Refresh

Intermediate to Advanced 14-20 hours $800-2,000

Full front and rear suspension rebuild for the 928, including the sophisticated Weissach rear axle on S4/GT/GTS models. Restores the grand tourer's excellent handling and ride quality.

Interval Every 60,000-80,000 miles or when handling degrades

Cost (DIY) $800-2,000

Labor 12-18 hours shop time

Parts List

Part	OEM Number	Aftermarket	Est. Cost
Front Strut (Each)	92834301502	Bilstein B4, Koni	$150-300
Rear Shock Absorber (Each)	92833030301	Bilstein B4, Koni	$150-280
Front Control Arm Bushing Set	92834199101	URO, Elephant Racing	$80-160
Front Strut Mount (Each)	92834302701	URO, aftermarket	$60-120
Front Ball Joint (Each)	92834153201	Lemforder, Meyle	$50-100
Tie Rod End (Each)	92834703301	Lemforder, Meyle	$50-90
Weissach Bushing Kit (S4/GTS)	Various	Elephant Racing, URO	$150-300
Rear Toe Link (Each)	92833104700	Lemforder, URO	$80-150
Rear Trailing Arm Bushing (Each)	92833114102	URO, aftermarket	$50-100
Sway Bar End Link (Front, Each)	92834306902	URO, aftermarket	$35-70

Tools Needed

Floor jack and jack stands rated for vehicle weight
19mm socket for lug bolts
18mm, 19mm, 21mm, 24mm sockets and wrenches
Pickle fork or ball joint separator
Spring compressor (front struts)
Torque wrench (ft-lbs range)
Bushing press or hydraulic press
Penetrating oil (PB Blaster)
Alignment tool set (optional)
Breaker bar for stubborn fasteners
Large pry bar for control arm manipulation

Procedure

Raise vehicle and support securely on jack stands under reinforced jacking points.
Remove all four wheels and set aside.
Document current ride height and alignment settings before disassembly.
Begin with front suspension - disconnect sway bar end links.
Remove tie rod ends from steering knuckle using pickle fork.
Remove front ball joints from control arms.
Support the strut assembly before removing top mount bolts.
From inside the hood, remove the three strut top mount nuts.
Remove strut assembly and use spring compressor to disassemble.
Replace strut cartridge, mount, and bearing as needed.
Reassemble strut and install in vehicle.
Replace front control arm bushings using press.
For rear suspension, identify if car has standard or Weissach axle.
Weissach axle (S4/GT/GTS) has multiple control arms and links.
Remove upper control arms - note any shim washers for alignment.
Remove lower control arms and toe links.
Replace all Weissach bushings - they affect handling significantly.
Replace rear shock absorbers - access through wheel well.
For non-Weissach models, replace trailing arm bushings.
Reassemble in reverse order, torquing all fasteners to spec.
Front control arm bolts: 63 ft-lbs (85 Nm).
Weissach control arm bolts: 74 ft-lbs (100 Nm).
Strut top mount: 44 ft-lbs (60 Nm).
Install wheels and torque lug bolts to 96 ft-lbs (130 Nm).
Professional alignment is essential - the 928 has many adjustment points.

Pro Tips

The 928's Weissach rear axle provides passive rear steering for stability.
Worn Weissach bushings cause unpredictable handling at the limit.
Elephant Racing offers excellent polyurethane bushing kits.
Bilstein B4 or Koni adjustables are popular shock upgrades.
The 928 is heavy (3,400+ lbs) - ensure proper support during work.
Check wheel bearings while suspension is disassembled.
Consider lowering springs (H&R, Eibach) if updating for performance.

⚠️ Warnings

The 928 is heavy - use appropriately rated jack stands.
Spring compressors are dangerous - ensure proper safety.
The Weissach axle is complex - take photos and label everything.
Worn Weissach components can cause dangerous handling at speed.
Always tighten suspension fasteners with weight on wheels.
Professional alignment is required after rear suspension work.

References

Rust Prevention and Repair

Intermediate to Advanced 8-40+ hours depending on severity $200-3,000+

Comprehensive guide to inspecting, preventing, and repairing rust on the 928. Covers common problem areas including rocker panels, floor pans, rear quarters, and battery areas critical to this galvanized but still vulnerable GT car.

Interval Annual inspection, repair as needed

Cost (DIY) $200-3,000+

Labor Varies significantly by extent of rust

Parts List

Part	OEM Number	Aftermarket	Est. Cost
Rocker Panel (Left)	92850349100	Reproduction available	$400-800
Rocker Panel (Right)	92850349200	Reproduction available	$400-800
Floor Pan Repair Section	Various	Fabricated panels	$200-500
Rear Quarter Repair Panel	Various	Reproduction	$300-700
Battery Tray	92861213100	Fabricated	$100-250
Door Skin (If needed)	Various	Reproduction limited	$400-900
POR-15 Rust Preventive Coating	N/A	POR-15	$40-80
3M Underseal Rubberized Coating	N/A	3M	$15-25
Weld-Through Primer	N/A	Eastwood, 3M	$15-30
Body Seam Sealer	N/A	3M, Eastwood	$20-40

Tools Needed

Wire brush and wire wheel attachments
Angle grinder with cutting and grinding discs
MIG welder (minimum 140A recommended)
Body panel clamps and magnets
Aviation snips for sheet metal
Sandblaster or chemical rust remover
Seam sealer applicator gun
Body filler and spreaders
DA sander with various grit discs
Spray gun for primer and underseal
Safety equipment: welding helmet, gloves, respirator

Procedure

Thoroughly clean undercarriage with pressure washer to expose rust areas.
Raise vehicle and inspect all common rust locations systematically.
The 928 has galvanized body panels but still develops rust over time.
Check rocker panels by pressing firmly - soft spots indicate internal rust.
Inspect battery tray area for acid damage and corrosion.
Examine floor pans from inside with carpet removed and from below.
Check rear quarters near wheel wells for stone damage and rust.
Inspect door bottoms and under side moldings.
Check suspension mounting points for structural rust.
For surface rust: sand to bare metal, treat with rust converter, prime and seal.
For perforation rust: cut out affected area 1 inch beyond visible rust.
The 928's galvanizing makes welding more challenging - clean thoroughly.
Fabricate or purchase repair panels to fit openings.
Apply weld-through primer to mating surfaces.
Tack weld panels in place, checking fit frequently.
Finish weld using stitch welding to prevent warpage.
Grind welds smooth and apply seam sealer to all joints.
Treat interior surfaces with rust preventive (POR-15 or equivalent).
Apply rubberized underseal to exterior underbody surfaces.
Prime and paint repaired areas to match existing finish.
Apply cavity wax to all hollow sections for ongoing protection.

Pro Tips

The 928 has galvanized body panels - less rust-prone than other cars of the era.
Rust often starts where galvanizing was damaged by stone chips or scratches.
Battery acid damage is common even with relocated batteries (spills during service).
Door bottoms and rocker panels are most vulnerable to water intrusion.
Reproduction panels are limited - fabrication may be necessary.
Consider professional inspection before purchasing to assess rust severity.
The 928's value is increasing - quality repairs are worthwhile.

⚠️ Warnings

Extensive rust repair can still exceed the vehicle's value on early cars.
Welding galvanized metal produces toxic fumes - work outdoors or with excellent ventilation.
Welding near fuel lines and tank requires proper safety precautions.
Improper structural repairs can affect crash safety.
Rust preventive coatings require proper ventilation and safety equipment.
Disconnect battery and fuel system before any welding operations.

References

Electrical System Restoration

Intermediate to Advanced 8-24 hours depending on scope $200-1,500

Complete guide to diagnosing and restoring the 928's electrical system. Covers the engine wiring harness, DME system, vacuum-controlled accessories, pop-up headlight mechanisms, and instrument cluster critical to this complex grand tourer.

Interval Inspect every 2-3 years, service as needed

Cost (DIY) $200-1,500

Labor 6-20 hours shop time

Parts List

Part	OEM Number	Aftermarket	Est. Cost
Engine Wiring Harness (Rebuilt)	Various by year	Specialist rebuilt	$500-1,500
Harness Repair Kit	N/A	Various suppliers	$50-150
DME Relay	92861510100	Bosch	$40-80
Fuel Pump Relay	92861510101	Bosch	$35-70
Alternator (Rebuilt)	92860301502	Bosch rebuilt	$250-500
Headlight Motor	92863110100	Rebuilt available	$150-300
Headlight Cable	92863120300	Aftermarket	$40-80
Instrument Cluster Capacitor Kit	N/A	Various	$30-70
Odometer Gear Kit (Brass)	N/A	Various	$20-50
Ground Wire Kit	Various	Custom fabrication	$50-120

Tools Needed

Digital multimeter with amp clamp
12V test light
Wire crimping tool set
Soldering iron and electronics solder
Heat shrink tubing assortment
Dielectric grease
Battery terminal cleaner
Small picks and probes for connectors
Wire strippers
Electrical contact cleaner
Heat-resistant wire loom and tape
Torx and Phillips screwdrivers

Procedure

Disconnect battery before any electrical work - negative terminal first.
Test battery condition - load test and check voltage (should be 12.6V resting).
Clean and tighten all battery connections with terminal cleaner.
Test alternator output - should be 13.8-14.4V at idle.
The 928 engine harness is a common failure point - inspect thoroughly.
Look for cracked, brittle, or heat-damaged insulation in the engine bay.
If harness is damaged, consider professional rebuild or replacement.
For minor damage, wrap affected areas with heat-resistant loom.
Locate the fuse/relay panel - test DME and fuel pump relays.
Check and clean all ground connections throughout the vehicle.
Main engine ground connections should be cleaned to bare metal.
Test and service pop-up headlight motors and cables.
Lubricate headlight pivot points with white lithium grease.
Replace stretched or frayed headlight cables.
For instrument cluster issues, remove and inspect circuit board.
Resolder cold solder joints and replace failed capacitors.
Replace odometer gears with brass upgrade kit if stuck.
Test all vacuum-operated electrical components (locks, HVAC).
Inspect and clean all multi-pin connectors.
Apply dielectric grease to all cleaned connections.
Add heat shielding to protect harness from exhaust heat.
Reconnect battery and test all systems.

Pro Tips

The 928's engine harness deteriorates from heat - this is the #1 electrical issue.
Rebuilt harnesses are available from 928 specialists and are worthwhile.
The instrument cluster has known issues - capacitor and solder joint repair is common.
Pop-up headlights require regular lubrication for reliable operation.
The 928 uses vacuum for door locks, HVAC, and cruise - check vacuum lines too.
Ground connections are critical - clean and protect them.
Document any wiring changes with photographs for future reference.

⚠️ Warnings

Always disconnect battery before working on electrical systems.
The 928 may have airbags (later models) - wait 10 minutes after disconnecting battery.
Engine harness work near hot exhaust requires care - engine must be cold.
Incorrect relay replacement can damage the DME computer.
Static electricity can damage electronic components - ground yourself.
Some 928 electrical components are expensive and hard to find - test before replacing.

References

Interior Restoration

Intermediate 16-40 hours for complete restoration $600-3,500+

Comprehensive interior restoration guide for the 928. Covers leather seat repair, carpet replacement, door panel restoration, dashboard care, and HVAC system service to return this luxury grand tourer's cabin to pristine condition.

Interval As needed based on condition

Cost (DIY) $600-3,500+

Labor 12-30 hours shop time

Parts List

Part	OEM Number	Aftermarket	Est. Cost
Leather Seat Cover Kit (Per Seat)	Various by color	Leatherique, Alea Leather	$400-1,000
Carpet Set	Various by color	Autoloc, aftermarket	$400-900
Door Panel Set	Various	Used or refurbished	$300-700
Seat Foam Cushion	Various	Various	$150-350
Leather Conditioner/Dye Kit	N/A	Leatherique, Connolly	$60-140
Door Seal Kit (Complete)	Various	German OEM suppliers	$300-700
Shift Boot (Auto/Manual)	Various	Aftermarket leather	$60-130
Sun Visor Set	Various	Used or refurbished	$100-250
Dashboard (If cracked)	Used only	Very limited	$500-1,500
HVAC Blend Door Servo	Various	Rebuilt	$100-250

Tools Needed

Trim panel removal tools (plastic pry bars)
Torx driver set (T20, T25, T30)
Hog ring pliers and hog rings
Heat gun for leather work
Leather cleaning brushes
Interior detailing brushes
Spray bottle for cleaning solutions
Seam roller for carpet installation
Steam cleaner (optional but helpful)
Rivet gun for door panels
Upholstery adhesive

Procedure

Remove seats by unbolting from floor (4 bolts per seat, 13mm).
Disconnect electrical connectors for power seats and heated seats.
The 928 has excellent leather seats that respond well to conditioning.
Clean seats thoroughly with quality leather cleaner.
For worn leather: apply Leatherique or similar conditioner system.
For cracked/torn leather: professional reupholstery or cover kit.
Remove hog rings to separate leather from foam if recovering.
Replace foam cushions if compressed - common on driver's side.
Install new covers using hog rings at attachment points.
Remove door panels by removing screws and popping clips.
The 928 door panels are well-made but clips become brittle.
Clean or replace door panel leather/vinyl as needed.
Remove old carpet by removing sill plates, console, and seat bases.
Clean and treat floor pan with rust preventive if any bare metal.
Install new carpet kit, starting from rear and working forward.
The 928 dashboard can crack - prevent with dashboard pad.
If dashboard is cracked, used replacement is only option.
Clean dashboard with appropriate cleaner - avoid silicone products.
Service HVAC system - test blend door servos and vacuum operation.
Replace blend door servos if clicking or not responding.
Replace blower motor if noisy or weak airflow.
Test all interior functions before final assembly.

Pro Tips

The 928 has luxury interior - often cleaning and conditioning is sufficient.
Leatherique can revive very dried and cracked leather.
The 928 dashboard is prone to cracking - used replacements are very expensive.
Prevent dashboard cracks with quality dashboard pad and window tinting.
Door panel clips are fragile - have extras on hand before removal.
The 928's HVAC uses vacuum servos - check vacuum system too.
Power seat tracks should be lubricated while seats are out.
The 928's carpets are complex - take photos before removal.

⚠️ Warnings

Later 928s have airbags - disconnect battery and wait 10 minutes before working near steering wheel.
Power seat motors carry significant current - disconnect battery first.
Leather dyes can stain surrounding surfaces - mask carefully.
Silicone-based products leave residue that interferes with future repairs.
Dashboard replacement is a major undertaking - consider professional help.
Heat gun can damage leather if held too close - keep moving.

References

Parts & Suppliers

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Helpful Tools

928 Spec Database Comprehensive 928 specifications, production numbers, and technical data Porsche Parts Diagrams Pelican's parts diagrams help identify correct part numbers by year 928 International Tech Library Extensive DIY guides and technical articles specific to the 928

Torque Specifications

Factory torque values for common service items

Reference Sources

Engine

Component	Torque Spec	Notes
Cylinder Head Bolts (S4/GTS)	Torque-to-yield sequence	See manual for multi-stage procedure
Timing Belt Tensioner	33 ft-lbs (45 Nm)	-
Timing Belt Rollers	33 ft-lbs (45 Nm)	-
Spark Plugs	22 ft-lbs (30 Nm)	-
Cam Tower Bolts	7 ft-lbs (10 Nm)	Tighten evenly in pattern
Oil Drain Plug	22 ft-lbs (30 Nm)	Replace washer
Water Pump Bolts	15 ft-lbs (20 Nm)	-
Intake Manifold Bolts	7 ft-lbs (10 Nm)	-

Suspension

Component	Torque Spec	Notes
Wheel Lug Bolts (M14)	96 ft-lbs (130 Nm)	Tighten in star pattern
Front Control Arm Bolts	63 ft-lbs (85 Nm)	-
Weissach Axle Control Arms	74 ft-lbs (100 Nm)	S4/GTS only
Tie Rod Ends	33 ft-lbs (45 Nm)	Use new cotter pin
Strut Top Mount	44 ft-lbs (60 Nm)	-

Brakes

Component	Torque Spec	Notes
Caliper Bolts	63 ft-lbs (85 Nm)	-
Brake Line Fittings	11 ft-lbs (15 Nm)	Do not overtighten

DIY Maintenance Guides

Step-by-step tutorials for common maintenance tasks

Oil Change

Easy 45 min $60-90

Complete V8 oil and filter change procedure.

Interval Every 5,000-7,500 miles

Cost (DIY) $60-90

Tools Needed

19mm socket for drain plug
Oil filter wrench
Drain pan (2 gallon capacity)
Funnel
Jack and jack stands or ramps

Procedure

Warm the engine for 2-3 minutes to thin the oil.
Raise the front of the car safely or drive onto ramps.
Locate the oil drain plug on the oil pan - passenger side.
Position the drain pan and remove the 19mm drain plug.
Allow oil to drain completely - at least 15 minutes for the V8.
The spin-on oil filter is on the passenger side of the engine, accessible from below.
Using the oil filter wrench, remove the old filter.
Apply a thin film of fresh oil to the new filter's gasket.
Thread the new filter on by hand until seated, then 3/4 turn more.
Replace the crush washer on the drain plug.
Reinstall drain plug and torque to 22 ft-lbs (30 Nm).
Lower the car and add 8-9 quarts of 15W-50 or 20W-50 oil.
Start engine and check for leaks at drain plug and filter.
Shut off, wait 3 minutes for oil to settle, check level and top off.

Pro Tips

The 928 V8 holds 8-9 quarts depending on model year and oil cooler.
Use quality synthetic 15W-50 for hot climates or track use.
Check for oil leaks at cam tower gaskets while under the hood.

Pop-Up Headlight Lubrication

Easy 30 min $10-20

Keep your pop-up headlights operating smoothly with regular lubrication.

Interval Every 6 months or annually

Cost (DIY) $10-20

Tools Needed

White lithium grease spray
Clean rags
Flashlight
Small brush

Procedure

Turn on the headlights to raise them to the up position.
Turn off the engine and headlights, leaving them raised.
Open the hood for access to the headlight mechanisms.
Locate the headlight pivot points on each side.
Clean old grease and debris from the pivot points and linkages.
Apply white lithium grease to all pivot points.
Lubricate the cable pulleys and guide tracks.
Apply grease to the motor output shaft area (accessible with brush).
Operate the headlights up and down several times to distribute grease.
Wipe away any excess grease that could attract dirt.
Check that both headlights operate at the same speed.
If one is slower, inspect cable tension and motor condition.

Pro Tips

Slow or uneven headlight operation usually means it's time for lubrication.
Don't use WD-40 - it's not a lubricant and attracts dust.
If headlights still operate slowly after lubrication, check motor brushes.
Stretched or frayed cables should be replaced, not just lubricated.

Brake Pad Replacement

Easy 1-2 hours $100-180

Front and rear brake pad replacement with rotor inspection.

Interval Every 25,000-40,000 miles

Cost (DIY) $100-180

Tools Needed

19mm socket for lug bolts
7mm Allen socket for caliper pins
C-clamp or brake piston tool
Wire brush
Brake cleaner
Brake grease
Jack and jack stands

Procedure

Loosen lug bolts while the car is on the ground.
Raise and support the car safely on jack stands.
Remove wheel to access the caliper.
Remove the two caliper guide pin bolts (7mm Allen on most).
Swing the caliper up and support it - never let it hang by the hose.
Remove the old pads from the caliper bracket.
Inspect rotor for scoring, cracks, or thickness below minimum.
Clean the pad contact surfaces with wire brush.
Open brake fluid reservoir, then compress caliper piston.
Apply brake grease to pad backing plate edges.
Install new pads in the bracket.
Swing caliper back over pads and reinstall guide pin bolts.
Torque caliper bolts to 63 ft-lbs (85 Nm).
Reinstall wheel and torque lug bolts to 96 ft-lbs (130 Nm).
Repeat for all corners.
Pump brake pedal until firm before driving.

Pro Tips

The 928 uses large brakes with good pad life.
Bed in new pads with moderate stops - avoid panic stops for 100 miles.
Consider upgrading to ceramic or performance pads for less dust.

Vacuum System Inspection

Easy 1 hour $30-80 for replacement hoses

Inspect and identify cracked vacuum lines that cause various system failures.

Interval Annually or when systems malfunction

Cost (DIY) $30-80 for replacement hoses

Tools Needed

Flashlight
Inspection mirror
Vacuum line kit (various sizes)
Vacuum gauge (optional)
Carburetor cleaner for leak detection

Procedure

Start with the engine cool and off.
Open the hood and locate the main vacuum reservoir and distribution block.
Visually inspect all visible vacuum lines for cracks, hardening, or collapse.
Check the lines running to HVAC controls (often behind the dashboard).
Inspect vacuum lines to the cruise control system.
Check vacuum lines to the door lock actuators.
Look for lines connected to the brake booster.
With engine running, listen for hissing (vacuum leaks).
Spray carburetor cleaner near suspect areas - idle change indicates leak.
Replace any cracked or hardened lines with proper size vacuum tubing.
Mark replaced lines with tape or tie for future reference.
Test affected systems after repairs (HVAC, locks, cruise, brakes).

Pro Tips

The 928 uses vacuum for HVAC, door locks, cruise control, and brake booster.
Original vacuum lines become brittle after 25+ years.
A failed vacuum system can cause multiple seemingly unrelated failures.
Consider replacing all vacuum lines as preventive maintenance.

Community Resources

Popular YouTube channels, forums, and communities dedicated to the 928

Porsche 928

Buyer's Guide

Overview

Quick Facts

Model Variants

928 / 928S

928 S4

928 GT

928 GTS

Pre-Purchase Inspection Checklist

Engine (Critical)

Transmission & Drivetrain

Suspension & Steering

Electrical & Systems

Body & Interior

Pricing Guide

Project Car

Driver Quality

Excellent

Concours / Collector

Red Flags - Walk Away If...

What to Look For

Ownership Costs

Expert Tips

Common Issues

Timing Belt Failure

Estimated Repair Costs

Common Fixes

Common Parts

Similar Issue On Other Models

Cam Tower Gasket and Oil Leaks

Estimated Repair Costs

Common Fixes

Common Parts

Engine Wiring Harness Deterioration

Estimated Repair Costs

Common Fixes

Common Parts

Automatic Transmission Issues

Estimated Repair Costs

Common Fixes

Common Parts

Cooling System Failures

Estimated Repair Costs

Common Fixes

Common Parts

Vacuum System Deterioration

Estimated Repair Costs

Common Fixes

Common Parts

Weissach Axle Suspension Wear (S4/GTS)

Estimated Repair Costs

Common Fixes

Common Parts

Pop-Up Headlight Failure

Estimated Repair Costs

Common Fixes

Common Parts

Instrument Cluster and Electronics

Estimated Repair Costs

Common Fixes

Common Parts

Air Conditioning System Failures

Estimated Repair Costs

Common Fixes

Common Parts

Restoration Guides

Complete Suspension Refresh

Parts List

Tools Needed

Procedure

Pro Tips

⚠️ Warnings

References

Rust Prevention and Repair

Parts List

Tools Needed

Procedure

Pro Tips

⚠️ Warnings