Hi Folks

my 89 XJSV12 has a strange groaning sound when revs close to idle and subsides when under load (I.e as accelerator is pressed sound disappears). It appears to be coming from the engine bay, but it's very difficult to pinpoint exactly.

When you switch off the ignition, the volume of the groan increases momentarily. Appreciate this is a bit of a weird and non specific issue, but it's driving me nuts! Car is otherwise running perfectly.


The only time I've experienced a similar issue was when the harmonic balancer went bad on my 94 6L V12, I.e. the sound was the same, but only lasted for a few seconds after startup.

I don't think this is a loose belt or bearing issue. If I were to guess, I'd say it sounded like an "air" issue...going by the sound.

Any ideas would be appreciated.

Stuart

 

Have you run over somebody and not realised?
Could be that you can only hear them at tickover.
Could it be an air filter blockage or breaking up?

 

Power steering? Check fluid and see if noise changes if wheel is turned.

 

Also, tighten up the inlet manifold nuts, this might be an airleak

 

I have had a weird groan now and then, which I now am pretty sure comes from the driver side fan. Yes, the one placed in the dashboard. It became very loud a few weeks ago and then dissappeared complety. For a while of course, it is Lucas parts after all...

The increase in noise you get when turning of the engine could come from a resonance in the fan spinning down.
In case your climate control works it should be easy to check by changing fan speed or turning them off.

 

I'm one of the least mechanically inclined guys here, but I've experienced the same thing in a few XJSs - noise was coming from the center dash vent. Vacuum related.

 

The engine cooling system can moan and groan....or even gurgle. Fluid harmonics, cavatation and all that....I can't explain the science of it very well, especially on one cuppa coffee.

And the noise can occur after shutdown.

If you think this is a possibility try bleeding the cooling system.

And, while we're on the subject, the V12 oiling system can moan and groan, particularly on a cold engine. Jaguar issued a TSB on this odd noise saying it was of noise consequence

Cheers
DD

 

 

*of no consequence




Cheers
DD

 

Exactly my problem. Under dash on RHS. No groan when cold. Louder as engine warms up. Steady throttle, it’s quite loud. Almost none at idle but when throttle touched, it appears. Butterflies are balanced. Air filters new. I’ve tried recording it without success. Sounds like an air leak from a large pipe. Any suggestions appreciated.