1978 Jaguar XJS
Browse our directory of 1978 Jaguar XJS vehicles. Access instant MOT history reports, tax status, and reliability insights for any registration listed below.
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Showing registrations 1–12 of 12 for the 1978 Jaguar XJS. Select any plate for an instant vehicle history check.
Common Problems & Reliability
The 1978 Jaguar XJS has 2 known issues. 2 of these are classified as serious faults that could be expensive to repair.
Inboard Rear Brake Caliper Seizure and Fluid Overheating
SeriousUntil mid-1993, all XJS models utilized inboard rear disc brakes mounted directly to the differential housing within the rear suspension subframe. Due to their close proximity to the hot differential and exhaust pipes, the brake calipers suffer from extreme heat soak, boiling brake fluid, and hardening hydraulic piston seals. Road grime and inaccessible location mean the calipers frequently seize, while differential output shaft oil leaks saturate the brake pads, causing severe brake fade, handbrake failure, and requiring a laborious complete rear subframe drop to repair.
Symptoms: Weak handbrake that fails to hold the car on a gradient, failing the annual UK MOT test, Spongy brake pedal and smoke or burning smell emanating from beneath the rear center of the car...
Est. repair cost: £650–£1,600
Floorpan, Jacking Point, and Radius Arm Mount Corrosion
SeriousThe XJS bodyshell is susceptible to hidden corrosion, particularly on cars built before the 1994 introduction of full galvanization. Road spray and blocked scuttle drains trap moisture within the double-skinned floorpans, sills, and front chassis legs. The rear suspension radius arm forward mounting points on the floor are especially vulnerable; rust here weakens rear axle location, creating dangerous instability under heavy braking and cornering that results in immediate MOT failure.
Symptoms: Rear-end twitchiness, steering deflection, or clunking under hard acceleration or braking, Soft, yielding metal or crunching noises when lifting the car on factory jacking points...
Est. repair cost: £800–£2,500
Buying Tips for the 1978 Jaguar XJS
- Prioritize post-1991 facelift models (and particularly post-1993 cars); they feature outboard rear disc brakes, galvanized steel panels, and far superior rust protection.
- On pre-1993 cars with inboard rear disc brakes, inspect the rear subframe for brake fluid leaks and caliper seizure; replacing neglected inboard pads and discs is a labor-intensive subframe-drop job.
- On 5.3 and 6.0-litre V12 models, ensure the cooling system has been regularly flushed and fitted with fresh thermostats; V12 engines tolerate zero overheating.
- Inspect V12 models built between 1989 and 1993 with Marelli digital ignition; ensure the distributor rotor and cap are inspected frequently to prevent single-bank misfires and catalytic converter fires.
- Check the structural floorpans, inner sills, and rear radius arm chassis mountings; repairs to rusty structural mounting points can run into thousands of pounds.
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