Porsche Carrera 4S
The M64/21 with VarioRam is the full promise of the last air-cooled 911: from about 5,000 rpm the variable intake opens and the engine pulls in a second wave with noticeable urgency — an effect affectionately known as the "VarioRam kick". The sound is distinctive, with the typical air-cooled boxer tone in the lower rev range and an almost shrieking top end to 6,800 rpm. Reliability-wise it's fundamentally robust like the 3.6 naturally aspirated, but regular oil checks are mandatory since oil leaks remain the classic Achilles heel of the range. Among 993s the VarioRam engine is considered the best naturally aspirated unit Porsche ever built for air cooling — the character is right, the mechanicals too.
Wide body with all-wheel drive
Turbo wide-body with naturally aspirated engine and all-wheel drive. Looks like a Turbo, sounds like the better 911. Wide track and VarioRam flat-six make the 4S a driving event.
Engine Weaknesses 8
Porsche recalled approx. 20,000 vehicles (model years 1995–1996): bio-based plastic wiring harness insulation hardens, cracks under heat and vibration — short circuit and engine failure possible. Check recall status before purchase.
Symptoms: Electrical faults, engine failure, irregular injection; in the worst case a smouldering fire in the engine bay.
Like the M64/05, the plastic valve covers are prone to leaking. Metal press-fit inserts work loose, oil drips onto the hot exhaust system. Check chain case gaskets at the same time.
Symptoms: Oil traces at the rear, whitish smoke after motorway driving, oil smell when switching off.
Age-related oil leak in the chain case area. Repair requires engine removal. Replace valve cover gaskets, spark plugs and oil pressure sender seal at the same time.
Symptoms: Oil film on underbody panelling, oil loss without visible external source, oil smell after driving.
The DME relay fails through continuous energisation and heat. Typical breakdown scenario: starter cranks, engine won't fire. Often occurs after heat soaking (summer, full sun). At night or after cooling down the engine starts again — replace the relay first.
Symptoms: Engine cranks but won't start; no fuel pump priming noise after ignition ON; problem after heat soak.
Valve guides wear under heat and high RPM. Excessive clearance draws oil along the valve stems into the combustion chamber. The cylinder head must be removed for boring and pressing in new guides.
Symptoms: Blue smoke on overrun and when lifting off the throttle; elevated oil consumption; oily spark plugs (cylinder-specific).
The vacuum-controlled resonance flaps of the VarioRam system can fail. Defective diaphragms in the vacuum actuator or porous control hoses prevent correct switching at 5,000 rpm.
Symptoms: Flat power delivery above 5,000 rpm, no characteristic VarioRam surge, rougher engine note.
The rocker shafts sit in a press-fit without a seal ring as standard. Oil seeps at the interface between shaft and cover material. Retrofit O-ring kit (RSR motorsport part) available — 12 rings per engine.
Symptoms: Oil film in the valve cover area; oil on hot engine components; smell after a short drive.
The PTFE guides on the VarioRam slider tubes wear and develop play. The characteristic power surge at around 5,000 rpm is absent or weaker.
Symptoms: Missing power kick above 5,000 rpm; flat power curve; drop-off in the upper rev range.
Vehicle Weaknesses 14
Steel brake lines are particularly vulnerable to corrosion in the underbody area. Corroded brake lines are a significant safety hazard — replace completely if any deterioration is found.
Windscreen and rear window frames are prone to rust, especially if windows were replaced incorrectly. Moisture ingress and adhesive residue accelerate the attack.
Hollow sections of the rear bumper supports rust from the inside due to dirt accumulation. Regular cleaning and cavity preservation are essential.
The climate control panel can remain permanently switched on due to leakage current, draining the battery within 48 hours. Repairing the blower motor and temperature sensor is usually cheaper than a new unit.
Aluminium brake calipers corrode heavily, especially during winter use or extended storage. Pistons seize, braking becomes uneven. Rebuilding or replacement is necessary.
Steering rack tends to develop oil leaks with age. On vehicles prior to 1996 with 18-inch wheels without the factory supplement, there is a risk of steering rack fractures.
Control arm and suspension bushings age considerably. Knocking and cracking noises when compressing and steering indicate worn rubber-metal elements.
Alternator wears with age. Diodes, voltage regulator and bearing wear are typical failure causes. Rebuilt exchange units are considerably cheaper than new parts.
Hydraulic clutch cylinders leak with age. Master and slave cylinders lose brake fluid, clutch pedal sinks through to complete failure.
Central locking tends to fail due to cold solder joints in the control unit and worn actuators. Locks or unlocks immediately after the remote signal is received.
Window regulator relay clicks inconsistently. Worn cables, defective switches or damaged cable pulls are the most common causes of failures in the aged 993.
Rubber engine mounts harden with age and lose their damping function. Vibrating sensation at the gear lever and increased body vibration at idle.
Exhaust system joints corrode heavily, especially at vibration points of worn engine mounts. High heat generation and moisture in the rear section accelerate the attack.
Door hinge straps wear out, causing creaking and squeaking when opening. Heavy doors and age-related material fatigue accelerate the wear.
Reports & Tests
24 owner complaints filed with NHTSA (1993–1998). Most reported: Electrical (6), Airbags (4), Engine & Cooling (3).