[anarkietown]

Hey guys,

For the past few months, my 2.3i automatic has been making a strange noise when below about 1000 RPM. It doesn't matter if the engine is warm or cold; whenever the RPMs drop below 1000 (like around 900 for a normal idle speed), I can hear a "purr purr purr" noise coming from the engine. I can also feel quite a bit of vibration through the steering wheel (more so than usual!).

I've looked at the engine while running, and when the revs are below 1000 RPM, the engine block appears to shake a little. A mechanic told me the noise and vibration is coming from the AC compressor, but it's not on, and hasn't been in a few months. I saw him put a large screwdriver between the engine and compressor, and the noise appeared to stop. He said he'd put in some spacers (after failing to be able to further tighten the bolts on the compressor).

Anyway, back to the sound: it sounds like a cat purring, or maybe even the sound that a Scottish person might make when pronouncing the letter "R". (Think groundskeeper Willie here )

Could my engine mounts be gone or going? Or could it be just a problem with the compressor mounting?

I'd rather it be the compressor mounting, since that seems like a much cheaper thing to fix...

 

[K9SAAB]

sounds a bit like the problem ive been battling with,although mine is more noticable with a cold engine.was also getting vibration at tick over,could feel it through the seat.mines been traced to the front engine mount,but I'd make very sure cos they aint cheap to renew

 

[Aeroman]

... and a bit like the 'feature' I have on my Aero as well. Vibration/resonance at tickover which stops above 1000rpm. I thought about the lower engine mounts, especially because they are covered in oil but a guy at Abbotts said the mounts are pretty robust. He said it could be due to the balancer shaft chain drive having jumped a tooth so that the shafts are out of sync. I have not had a chance to check this but still suspect one or other of the bottom mounts - the top mount bushes were done about 2 years ago when I got the car.

 

[ben hall]

Same happenned on my car, and I knew it wasn't the balance shaft chains cos they'd just been changed! Turned out to be the front lower engine mount (I think it was the front, could have been the back one) which had "gone soft" allowing excess vibration to be transmitted into the car. At anything other than idle it wasn't noticeable.