Recently purchased a 1990 XJS Conv.
30,000 miles, car is in excellent physical condition, Unfortunately the V-12 has definite issues.
Most recent, & Hopefully someone has seen this before !
Drove the car yesterday & it ran perfectly, Parked in garage last night, would not start this AM. starter would engage but not turn over.
I suspected a Hydro Lock ( as I have been experiencing coolant loss)
Pulled the plugs & tried starter still nothing.
Time to pull out the big guns,
Pulled the fan clutch off, put a socket & breaker bar on the Crank pulley & it wont budge!!!
Anyone ever heard of this before??

 

Welcome to the forum Burger,

I've copied this question from your Intro to XJS forum. Members here with the same model will be able to help.

Graham

 

Regrettably . . . only after a severe coolant loss, overheating event and resultant seized engine. All fingers and toes crossed that this has not happened to yours . . . but . . . assuming car has auto trans or is in neutral, and that spark plugs are still out, a locked crank has the smell of doom. You say it was running perfectly at switch-off the night before?

Best wishes,

Ken

 

yes ran perfectly prior to shut down. Temp normal
AC even working. Auto trans in N, plugs out & wont budge. Definitely scratching my head on this one

 

Not to make things worse but the stock temp gauge can be questionable at the best of times. Even today my car said it was on the brink of combustion...I pull over, the engine, hoses etc are barely hot to the touch, an hour later after restarting the car the gauge reads normal again. This has been the routine for a week now with different temps before/after restarting the car. Also tends to go hand in hand with my trip computer working/not working. Now I'm looking for a professional grade digital temp gauge.

Have you experienced any white smoke from exhaust or murky grey oil?

 

Out on a limb, my usual hang out.

You mentioned in the other post that you attempted to start with the starter motor, but it failed to rotate, the starter that is, soooooooo, maybe that starter is jamming the big thing in the middle, that be the real engine.

Rotating the V12 Anti-clockwise is fraught with DANGER, but a SMALL, as in 10mm of the crank pulley in that direction my just un-jam that sucker. You will hear the starter "clack" sort of as it releases its grip on the ring gear.

 

What gloom and doom could Burger/we experience if we rotate counter clockwise? This situation does not sound good lets hope it is indeed the starter. Good luck mate.

 

The Plastic chain tensioner can snap at the lower pivot point.

Some of these tensioners are already cracked from old age, so a rotation in that anti-clockwise CAN cause the chain to "catch up" on the top edge, and then "pull down" on the tensioner unit so easily its scary, and then the snap, that is silent.

I have rotated them backwards a small amount, and got away with it, and then some I have not, its like a Vegas moment.

The tensioner is about $600 last time I needed one, and that was a very long time ago, and the labour is HUGE, and MESSY.