IsItAGoodCar
Reliability Guide

Common Problems with the
1975 Jaguar XJS

Jaguar launches the revolutionary XJ-S grand tourer featuring the silky 5.3-litre V12, flying buttresses, and peerless high-speed continental refinement.

What changed for 1975

  • •Launch of the Malcolm Sayer-designed grand tourer with iconic flying buttress rear styling
  • •5.3-litre (285 bhp) all-aluminium V12 paired with Borg-Warner 3-speed automatic or rare 4-speed manual
  • •Introduction of the high-efficiency May Fireball HE cylinder head in 1981 boosting fuel economy by 20%
  • •Introduction of the Targa-style XJ-SC Cabriolet and the 3.6-litre AJ6 straight-six engine in 1983

Common MOT watch-outs

  • !Severe structural corrosion of the floorpans, sills, jacking points, and front chassis rails
  • !Inboard rear brake caliper seizure, pad contamination from differential oil, and handbrake failure
  • !Perished rear radius arm bushes causing rear-axle steer and suspension deflection
  • !Leaking power steering rack seals and corroded steel power steering cooler pipes
2
Known Issues
2
Serious
0
Moderate
0
Minor

All Known Issues

Inboard Rear Brake Caliper Seizure and Fluid Overheating

SeriousBrakes

Until 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.

Est. Repair Cost: £650–£1,600
Warning Signs:

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, Severe loss of rear braking efficiency and brake fluid weeping down the differential casing

What to Inspect:
  • Inspect the inboard brake discs and calipers through the rear subframe with an inspection torch for oil contamination
  • Check service history to see if the rear axle cage has been dropped for a comprehensive brake caliper overhaul
  • Confirm the vehicle build date; late 1993 to 1996 models feature easily serviced outboard rear disc brakes
Verified by IsItAGoodCar Research TeamUpdated

Floorpan, Jacking Point, and Radius Arm Mount Corrosion

SeriousBodywork & Rust

The 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.

Est. Repair Cost: £800–£2,500
Warning Signs:

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, Damp carpets in footwells and visible rust holes along outer sill returns and wheel arches

What to Inspect:
  • Inspect the underside of the floorpan where the rear suspension radius arm mounts attach to the body
  • Probe front inner wings, headlights bowls, and floorpans with a wooden or plastic probe for crumbling metal
  • Lift boot carpet to inspect battery tray floor and rear fuel tank support panel for structural rust
Verified by IsItAGoodCar Research TeamUpdated

Buying Tips for 1975 Jaguar XJS

  • Check all V12 engine valley fuel injector hoses; baked rubber lines crack and spray fuel, causing engine bay fires
  • Inspect inboard rear brake discs with a torch; if worn, factor in the substantial labour cost to drop the rear subframe
  • Examine front footwells and sills for dampness and hidden rust beneath thick interior sound-deadening underlay
  • Verify that air-conditioning functions; the GM Harrison A6 compressor and complex vacuum flaps require specialist maintenance
1976–1988
Check a 1975 Jaguar XJS by Registration