Porsche Carrera 4
The M64.01 is the transitional engine par excellence: 3.6 litres, 184 kW, the first 911 engine worldwide in identical specification for all markets. New cylinder heads, revised camshafts, twin-spark ignition — more than just a bored-out 3.2. Sonically more refined than the 930.20: richer, rounder in torque, less raw at idle. The core character isn't lost though — the boxer is unmistakable, just more grown up. The critical issue on early 964s (1990–mid 1992): the Freudenberg dual-mass flywheel. It develops internal play and often fails between 25,000 and 50,000 km — with noises alarmingly similar to a rod bearing. From mid-1992 the proven LUK flywheel, which is durable. Buying rule: either from mid-1992 or proof that the Freudenberg was replaced with LUK. Oil leaks are age-typical — moisture on valve covers and chain housing isn't alarming, drips are.
All-wheel makes it safer — but tamer too
The first production 911 with all-wheel drive — technically impressive, around 100 kg heavier than the C2. Pays dividends on alpine passes in the wet, but costs the playful lightness of the rear-wheel drive car. Röhrl preferred the C2 on the circuit, the C4 on snow. That says it all. C4 for year-round or wet mountain use. C2 for sporting character.
Engine Weaknesses 8
Age, thermal stress and Loctite bonding make the studs brittle. When they break, hot exhaust gases escape and permanently damage the cylinder head and liner. Engine overhaul costs €8,000–15,000.
Symptoms: Power loss in individual cylinders; compression loss; exhaust smell during operation; often only visible when removing the valve cover.
The high-pressure lines from the thermostat housing to the oil filter housing become brittle and corroded with age. If they burst while driving, the oil pump drains the sump in seconds — engine failure. Preventive replacement strongly recommended.
Symptoms: Oil spots in the right wheel arch; visible corrosion on hose crimp fittings; sudden oil pressure warning during driving.
At high mileage, the chain tensioners rattle on cold start until oil pressure builds up. Worn tensioners can be pushed in with two fingers. Timing chain replacement requires complete engine disassembly.
Symptoms: Metallic rattling for 2–5 seconds on cold start; noise fades once at operating temperature. With heavy wear also present when warm.
At high mileage, piston rings and cylinder bores wear out. All piston rings may be broken, pistons showing heat damage. Complete engine overhaul required.
Symptoms: Blue smoke under load and on overrun; oil consumption above 0.5 L/1,000 km; power loss due to compression drop.
The O-ring seals at the cylinder bases harden with age and start leaking. Oil collects on the aluminium blower housing below the cylinders. Early 964 units (up to approx. 1991) have no groove system — a labour-intensive retrofit solution is required.
Symptoms: Oil spots under the vehicle at the centre-rear; oil visible on aluminium duct parts below the cylinders; oil smell after driving.
The two relays in the DME control unit (fuel pump + Motronic) are permanently energised and fail from heat stress. The number one breakdown cause on the 964. Cheap to fix, but inconvenient when it happens on the road.
Symptoms: Engine cranks but won't start; no fuel pump priming noise after switching on the ignition.
The Freudenberg dual-mass flywheel (1990–1992) with rubber damping fails due to overheating; the rubber layer separates. From 1993 a more robust LUK unit with steel spring damping was fitted. Affected vehicles require DMF replacement.
Symptoms: Rattling and grinding noises at idle; strong vibrations at low RPM; shifting problems.
The magnesium coating on the lower valve covers flakes off and releases oil. Replacement aluminium covers without this coating are available. Repair kit approx. €299.
Symptoms: Oil drops after extended standing; oil film on underside of engine; oil smell after driving. Coating particles in the oil possible.
Vehicle Weaknesses 8
Especially on Cabriolet and Targa: weld seams at the windscreen-to-frame transition rust due to chassis flex. Repair requires windscreen removal.
ABS control unit located in the trunk. Connector pins corrode due to moisture ingress. Replacement costs up to €4,000. Preventive cleaning of the connectors is recommended.
The engine bay wiring harness of the 964 has become brittle with age. Insulation cracks on contact. Repairs by previous owners using unsuitable connections increase the risk of short circuits and fire.
Rubber bushings in the front control arms wear after approximately 80,000 km. Full control arm replacement necessary — bushings cannot be pressed in separately.
The 964 steering rack (the 911's first power steering) leaks at shaft seals and O-rings. Replacing the rack costs €1,000–3,000 depending on parts quality.
Synchro rings in the G50 gearbox wear with aggressive shifting. Typical symptom: grinding when engaging cold gears. Otherwise the G50 is considered low-maintenance with correct oil level.
Leaking battery acid attacks the battery tray in the trunk. Corrosion spreads beneath the trim and can penetrate structural areas.
Mechanical flaps at the heat exchanger outlets seize up over time. Broken cables lead to one-sided loss of warm air. Exhaust smell when heat exchangers are leaking.