Skip to content
MOTRS

XJ-S

1975-1996 / Coupe / Convertible / United Kingdom

All XJ-S problems All workshop issues
Common Engine, V12

Head gasket weeping

Symptoms

Coolant appears around the head gasket line (external weep), or coolant contaminates the oil (internal failure, mayonnaise under the filler cap, white exhaust smoke).

Cause

The V12 block and heads expand at different rates, stressing the gasket. Repeated thermal cycling, especially overheating events, causes the gasket to fail. External weeping is common on high-mileage engines and can be lived with if it's minor. Internal failure requires immediate action.

Fix

Both heads off, gaskets replaced, heads pressure-tested and skimmed if warped.

Use quality gaskets (Payen or genuine Jaguar).

The job is 30-40 hours of specialist labour.

Budget $8,000-12,000 AUD.

Cost mentioned in fix
Budget $8,000-12,000

Know something we don't?

Owned a Jaguar XJ-S? Share your experience with this issue. What worked, what didn't, costs, tips. Help the community.

Submit an update
// More XJ-S problems

Other known issues

Minor Engine, V12

Cooling system failure

Engine overheats, temperature gauge climbs into the red, coolant boils over. In severe cases, head gaskets fail and coolant enters the oil.
Common Engine, V12

Lucas ignition system failure (pre-1989)

Misfiring, rough idle, hard starting, power loss, sometimes total ignition failure.
Common Engine, V12

Marelli ignition issues (1989 onwards)

Similar symptoms to Lucas, misfiring, rough running, but less frequent and usually easier to diagnose.
Common Engine, V12

Fuel injection faults (V12)

Rough idle, hesitation, poor fuel economy (even worse than usual), hard starting, stalling.
Common Engine, V12

Exhaust manifold cracking (V12)

Ticking or blowing noise from the engine bay, exhaust smell, sometimes visible exhaust gas.
Common Engine, Six-Cylinder (AJ6/AJ16)

Timing chain tensioner failure

Rattle from the front of the engine on cold start, which may or may not settle when warm. In severe cases, the chain jumps a tooth and the engine runs badly or stops.
View all 23 XJ-S problems