Minor Transmission
GM TH400, generally bulletproof
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Submit an updateXJ-S
1975-1996 / Coupe / Convertible / United Kingdom
// More XJ-S problems
Other known issues
Common Transmission
Borg-Warner Model 66 automatic problems (early cars)
Harsh shifting, slipping, delayed engagement, overheating. The BW66 is simply not strong enough for sustained V12 power.
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
Head gasket weeping
Coolant appears around the head gasket line (external weep), or coolant contaminates the oil (internal failure, mayonnaise under the filler cap, white exhaust smoke).
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.