Porsche 928 928
Weaknesses, engine ratings and buying advice
The Porsche 928 (1977–1995) was Porsche's attempt to replace the 911 with a modern front-engined grand tourer — water-cooled V8, transaxle, 2+2 seating. It failed as a 911 successor but survived 18 years as a standalone icon. With 61,056 built, it is today an affordable classic demanding complex maintenance.
Engine range: Four evolutionary steps from 177 kW (M28.01">M28.01, 4.5L, 1977–1982) to 257 kW (M28.49">M28.49, 5.4L GTS, 1992–1995). The 16V SOHC engines (M28.01">M28.01–M28.21">M28.21) are mechanically simpler; the 32V DOHC engines from the S4 onward (M28.41">M28.41) are more powerful but more maintenance-intensive. ALL 928 engines use a rubber timing belt — this is the decisive purchase criterion.
THE issue: the timing belt. Reportedly the longest toothed timing belt ever fitted to a production car — it drives all camshafts, the oil pump and the water pump simultaneously. 32V engines (S4 from 1987 onward) are interference engines: belt snap = immediate valve damage = engine destroyed. Interval: 45,000–50,000 miles or 4–5 years, whichever comes first. Storage time counts — a 928 with 30,000 miles but a 10-year-old belt is a ticking time bomb. Timing belt + water pump + tensioners: $700–$1,600.
Transaxle: Engine up front, gearbox at the rear, connected by the torque tube. Torque tube bearings wear out around 60,000–80,000 miles and generate a speed-proportional drone. On automatic 928s: check the torque tube clamp bolts regularly (torque to 66 ft-lb) — loose bolts transmit axial thrust to the crankshaft thrust bearings → engine failure. The Mercedes-Benz 4-speed automatic (722-series) is fundamentally robust, but valve body wear sets in beyond 100,000 miles.
Body: Doors, front fenders and bonnet are aluminium — no classic rust, but galvanic corrosion at aluminium-to-steel contact points. Steel sills, wheel arches and door seal clips are particularly vulnerable. Sunroof seals fail → moisture in rear and boot area.
Electrics: Wiring harness insulation becomes brittle after 35+ years. Intermittent faults without obvious cause are usually corrosion at earth points. Instrument cluster flexible PCB track fails selectively. S4/GTS owners: the ABS hydraulic pump lives hidden in the left rear wheel arch and must be bled with the brakes — most owners never service it.
Buying guide: Timing belt service documentation is non-negotiable — no documentation means budget for an immediate belt change. GTS (M28.49">M28.49, 5.4L) is the most desirable variant (from $55,000 automatic; manual very rare). S4 with manual (M28.41">M28.41) is the most accessible entry point. Before buying: check engine oil for coolant contamination, cold and warm idle quality, belt documentation, torque tube clamp bolt condition (automatics). A correctly maintained 928 is one of the most characterful and comfortable classics for the money.
350 PS
928 GTS · Benzin
The masterpiece — 18 years of development, distilled
Legendary!301 PS
4.7L V8 Benzin
11 weaknesses
Stay Away!Engine Overview
The Porsche 928 928 is available with 5 engine variants — from 241 to 350 hp. 2 variants had engine changes — the model year is crucial.
Porsche's first production V8 — 4.5-litre SOHC with K-Jetronic injection. Solid base engine with decent refinement, but a modest 240 hp by today's standards. Regular oil changes and cooling system care are mandatory with these classics. Timing belt every 48,000 km (interference engine!) — the most important service interval. K-Jetronic warm-up regulator ages, warm-start problems. Valve clearance adjustment needed.
- !! Timing belt camshaft drive wear from 50,000 km
The 4.5L 16V engine (1977–1984) is a non-interference engine, however belt failure causes camshaft damage. Recommended replacement interval: 50,000 km or 5 years. Camshaft sprockets wear with incorrect belt tension.
Symptoms: No warning symptom on belt failure, engine misfires with belt wear, rough running - !! Camshaft and flat tappet wear due to incorrect oil viscosity from 100,000 km
The M28 uses a flat-tappet camshaft. Modern engine oil contains little ZDDP additive, which worsens lubrication of the sliding surfaces. The result is camshaft lobe wear.
Symptoms: Ticking noise from valve train, gradual power loss, camshaft wear visible on inspection - !! Water pump must be replaced at every timing belt change from 50,000 km
Water pump and timing belt have comparable service lives. Since the pump is only accessible via the timing belt, it must be replaced at every belt change. Pump failure leads to overheating.
Symptoms: Coolant loss, rising temperature gauge, steam from engine bay
+ 8 more engine weaknesses + vehicle weaknesses
Late version of the 4.5-litre SOHC with LH-Jetronic instead of K-Jetronic. 242 hp — slightly more than the early M28.01 (240 hp). More reliable than the K-Jetronic variant thanks to more modern injection. Same basic mechanicals, same maintenance requirements. Timing belt every 48,000 km (interference). LH-Jetronic more reliable on warm-up than K-Jetronic, but air mass sensor ages. Last SOHC generation with improved emissions.
- !! Timing belt age-related failure — non-interference engine from 50,000 km
The early 4.5L 16V M28.19 (up to 1984) is a non-interference engine, however belt failure causes severe camshaft damage. Age-related brittleness can cause the belt to fail even at low mileage.
Symptoms: No warning symptom, engine failure on belt break, engine loses all compression after belt failure - !! Camshaft flat tappet ZDDP deficiency in modern oil from 100,000 km
The early M28 uses a flat-tappet camshaft, which depends on high-viscosity, ZDDP-rich oil. Modern engine oil contains too few high-pressure additives, leading to camshaft lobe scoring.
Symptoms: Metallic ticking from valve train, measurable camshaft wear on inspection - !! Water pump and cooling system age-related damage from 50,000 km
Water pump must be replaced at every timing belt change. On vehicles over 40 years old, all coolant hoses should be renewed. A missing thermostat leads to immediate overheating.
Symptoms: Coolant loss, rising temperature display, steam from engine bay
+ 8 more engine weaknesses + vehicle weaknesses
GT version with 330 hp via sharper camshafts, optimised intake and higher compression. Mechanically identical to the S4 engine, just more aggressively calibrated. Rare and sought-after. Same maintenance requirements as the M28.41. Timing belt every 48,000 km (interference). 32-valve DOHC. GT-specific cams with more valve lift. Rarer engine — parts availability more limited than standard S4.
- !! Timing belt failure — 32-valve interference engine from 60,000 km
Identical to the S4 engine: interference engine with two timing belts. Belt failure destroys all 32 valves and pistons. Particularly painful in the rare GT — strictly observe the 60,000 km/4-year replacement interval.
Symptoms: Engine stops abruptly, loud metallic clattering, will not start again. - !! Thrust bearing wear (automatic) — crankshaft damage
Less common in the GT since most are manuals. But in the few automatic GT examples the TBF risk exists just as with the S4. Check crankshaft end float regularly.
Symptoms: Axial crankshaft play over 0.4 mm, dull knocking when accelerating/lifting off. - !! Camshaft sprocket wear at high revs
The GT is driven in the upper rev range more often than the S4. Camshaft sprockets wear faster, especially with track day use. Valve timing shifts gradually.
Symptoms: Power loss at high revs, light clattering from valve train, changed exhaust values.
+ 2 more engine weaknesses + vehicle weaknesses
The final and most powerful 928 engine: 5.4 litres, 350 hp, 500 Nm from 4,250 rpm. Wide-body bodywork, widened track. The GTS engine is long-lived and torque-rich; with good care, comfortably over 200,000 km. Timing belt every 60,000 km. Timing belt every 48,000 km (interference). 32-valve DOHC. The GTS is the most desirable and valuable 928 — only ~2,900 built. No tuning needed, perfectly calibrated from factory.
- !! Timing belt failure — 32-valve interference engine from 60,000 km
The 5.4-litre GTS is also an interference engine. On a GTS worth €80,000–150,000, the regular timing belt change (60,000 km/4 years) is non-negotiable. Check documentation on purchase.
Symptoms: Engine stops abruptly, loud metallic clattering, will not start again. - !! Thrust bearing wear (automatic) — crankshaft damage
The infamous 'Thrust Bearing Failure' also affects the GTS with automatic. The higher torque of the 5.4-litre increases the load. Check axial crankshaft play at every service.
Symptoms: Axial crankshaft play over 0.4 mm, dull knocking under load changes, metallic noises. - !! PSD/ABS hydraulic pump — GTS-specific
The PSD pump (Porsche Stability Device) on the GTS fails more often than on earlier models. Spare parts are rare and expensive. Aftermarket solutions and reconditioned pumps available from specialists.
Symptoms: ABS warning light, PSD warning light, altered traction control behaviour, pump audibly runs on after switching off.
+ 2 more engine weaknesses + vehicle weaknesses
First S version with 4.7-litre displacement and 300 hp — still SOHC, but significantly more powerful than the 4.5-litre. K-Jetronic injection. Solid mechanicals, mainly age-related wear topics. Keep oil change intervals conservative. Timing belt every 48,000 km mandatory (interference). Always change water pump and rollers too. K-Jetronic warm-start issues as M28.01. SOHC heads less complex than later DOHC.
- !! Head gasket — critical on overheating
The head gasket on the 4.7-litre can fail under overheating. The cause is often a defective thermostat or radiator cap. The V8 requires replacing both cylinder heads — a major labour job.
Symptoms: Coolant in the oil (milky oil cap), oil in the coolant, white smoke from exhaust, loss of compression in test. - !! Timing belt camshaft drive 32-valve interference engine from 50,000 km
From 1985 the 928 S has a 32-valve interference engine. Belt failure bends all valves. Replacement interval: 50,000 km or 5 years. Check camshaft sprockets for groove wear.
Symptoms: No warning symptom on belt failure; rough running or misfires with belt wear - !! Camshaft 32V flat tappet wear due to ZDDP deficiency from 100,000 km
The 32-valve engine has twin camshafts with flat tappets. Modern oil contains almost no ZDDP. Lack of high-pressure additives leads to lobe and tappet surface wear.
Symptoms: Metallic ticking from valve train, gradual power loss, camshaft shows scoring on inspection
+ 8 more engine weaknesses + vehicle weaknesses
Evolution of the 4.7-litre to 310 hp with DOHC cylinder heads and LH-Jetronic. Noticeably more rev-happy than the SOHC predecessor. Reliable, but like all 928 engines dependent on regular maintenance. Timing belt every 48,000 km (interference). DOHC heads: more power but more complex valve adjustment. LH-Jetronic. Hydraulic lifters — less manual adjustment than SOHC but clatter on old oil.
- !! Timing belt failure — interference engine from 60,000 km
From the DOHC 4.7-litre onwards the M28 is an interference engine: timing belt failure destroys valves and pistons. Replacement interval 60,000 km or 4 years — ignoring this risks total engine damage.
Symptoms: Engine stops abruptly, mechanical clattering from valve train, engine will not start again. - !! Head gasket failure on overheating
The DOHC engine's head gasket fails under overheating. Often caused by a worn thermostat or burst coolant hose. Replacing both cylinder heads on the V8 means an extremely high labour bill.
Symptoms: Mayonnaise-like residue on oil cap, coolant loss without visible leakage, white exhaust smoke, engine overheats quickly. - !! Timing belt 32V interference engine every 50,000 km from 50,000 km
The 928 S4 M28.21 has a 32-valve interference engine. Belt failure destroys all 32 valves. Porsche recommends 60,000 km, specialists recommend 50,000 km or 5 years. Check camshaft sprockets for wear.
Symptoms: No warning symptom, engine failure on belt break, occasionally a slapping noise shortly before failure
+ 8 more engine weaknesses + vehicle weaknesses
Major update to 5.0 litres with 32-valve heads and LH-Jetronic. 320 hp, massive torque from 3,000 rpm. The S4 engine is considered the most reliable 928 powerplant — mature and long-lasting with proper maintenance. Change the timing belt every 60,000 km. Timing belt every 48,000 km (interference). 32-valve DOHC with hydraulic lifters. Water-cooled alternator. The GTS variant (M28.49) gets sharper cams and 350 hp.
- !! Timing belt failure — 32-valve interference engine from 60,000 km
The 32V engine is an interference engine with two timing belts. Belt failure destroys all 32 valves and often the pistons too. Strictly observe the replacement interval of 60,000 km/4 years. Repair cost for consequential damage: €8,000–15,000.
Symptoms: Engine stops abruptly, loud metallic clattering, will not start again. With gradual stretch: rough running, shifted valve timing. - !! Thrust bearing wear (automatic) — crankshaft damage
In automatic models, the crankshaft thrust bearings wear due to torque converter clutch reversals. In extreme cases the crankshaft seizes into the engine block. The infamous 'Thrust Bearing Failure' (TBF) is the most expensive 928 damage.
Symptoms: Axial crankshaft play over 0.4 mm (measurable), dull knocking when accelerating/lifting off, metallic noises from engine. - !! LH-Jetronic: airflow meter and throttle body
The hot-wire airflow meter (AFM) and throttle position sensor on the LH-Jetronic fail or produce incorrect readings. Cold-start problems and power loss result.
Symptoms: Rough idle, power hole when accelerating, engine stalls, engine warning light, poor throttle response.
+ 2 more engine weaknesses + vehicle weaknesses
Vehicle Weaknesses
| Weakness | Cost | |
|---|---|---|
| Wiring Harness Deterioration (Engine Bay + Vehicle Network) Cable insulation and connectors throughout the entire wiring harness become brittle and cracked after 30–40 years. High contact resistance at corroded terminals causes multiple intermittent faults. Symptoms: Obscure starting problems, fluctuating instruments, false warning lights, ignition misfires without clear cause. | High | |
| Instrument Cluster — Circuit Foil and Solder Joints Faulty The flexible circuit foil in the instrument cluster cracks with age. Over 30 bulbs in the cluster; failed solder joints cause partial loss of individual gauges. Refurbishment by specialists is possible. Symptoms: Individual instruments non-functional, flickering displays, speedo or rev counter jumping or dropping out. | Medium | |
| LH-Jetronic Cold-Start Problems (S4/GT/GTS 1987–1995) The LH-Jetronic system on the 32V engine ages at multiple points simultaneously: mass airflow sensors drift, Temperature Sensor II fails in cold conditions, LH/EZK relays corrode. Intermittent starting problems and rough idle result. Symptoms: Poor cold start, rough idle below 90°C, engine stumbles on initial throttle application, stalling shortly after cold start. from 80,000 km | Medium |
Top Reported Issues
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Known Problems and Issues +
A total of 74 weaknesses have been documented for the Porsche 928 928 (1977–1995) — 59 engine-related and 15 vehicle-related. 3 problem engines: M28.01 (4.5L V8), M28.11 (4.7L V8), M28.21 (4.7L V8). Typical issues affect Electronics, Suspension, Brakes, Body.
928 (M28.01, 1977–1982) — Stay Away!: Timing belt camshaft drive wear, Camshaft and flat tappet wear due to incorrect oil viscosity, Water pump must be replaced at every timing belt change. Power: 240 PS.
928 (M28.11, 1979–1983) — Stay Away!: Head gasket — critical on overheating, Timing belt camshaft drive 32-valve interference engine, Camshaft 32V flat tappet wear due to ZDDP deficiency. Power: 300 PS.
928 (M28.21, 1983–1986) — Stay Away!: Timing belt failure — interference engine, Head gasket failure on overheating, Timing belt 32V interference engine every 50,000 km. Power: 310 PS.
928 (M28.19, 1983–1986) — Be Careful: Timing belt age-related failure — non-interference engine, Camshaft flat tappet ZDDP deficiency in modern oil, Water pump and cooling system age-related damage. Power: 242 PS.
928 (M28.41, 1986–1991) — Be Careful: Timing belt failure — 32-valve interference engine, Thrust bearing wear (automatic) — crankshaft damage, LH-Jetronic: airflow meter and throttle body. Power: 320 PS.
928 (M28.47, 1989–1991) — Be Careful: Timing belt failure — 32-valve interference engine, Thrust bearing wear (automatic) — crankshaft damage, Camshaft sprocket wear at high revs. Power: 330 PS.
928 (M28.49, 1991–1995) — Be Careful: Timing belt failure — 32-valve interference engine, Thrust bearing wear (automatic) — crankshaft damage, PSD/ABS hydraulic pump — GTS-specific. Power: 350 PS.
What to watch out for with the Porsche 928? See the detailed listing of all engine and vehicle weaknesses in the sections above.
Frequently Asked Questions
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Last updated: February 2026 · All information without guarantee