944 Turbo - vibration when cold

[Hallsy]

I have a slightly odd problem with my 944 Turbo.

During the winter I have noticed that on particuarly cold days (say 2'c or less) upon startup I get vibration from the right hand side of the engine bay. Only at idle (around 950rpm), in cold weather with a cold engine. If we have a few days at around 5'C there is no vibration.

The vibration goes if I increase revs to 1200rpm, and is also gone as soon as the engine has warmed up a little, it only takes a mile or so of driving before the vibration has gone.

My first thoughts are engine mount - but why would this be effected by the ambient temperature? I know the LH one has been done not too long ago, but no record for the RH one. However, I did take a quick look at the dizzy cap with respect to the headlight bar, and the top screw looks to be above it - I remember JMG saying some time ago that if the upper dizzy cap screw is below the headlight bar, then it is a sign of the mount collapsing.

I do believe I have a leak from the front of the exhaust from when I made contact with a speed hump that I mis judged, and wonder if it is the sound of the exhaust touching the car.

Hoping to get out and take a look this coming weekend (work and my 9-5 Aero took up last weekend!), but wondered if anyone had had similar issues?

 

[Monkeythree]

I'm guessing here but given that the engine mounts are oil filled, could it be related to the oil being thicker when cold and thinner when warm i.e. the natural frequency of the engine mount varies with temperature?

 

[Hallsy]

Yes - you could be on to something there.

It fits the usual failure mode for engine mounts, just not often heard of the problem being worse in cold weather!

Another job to add to the list, lol!

 

[edh]

Could be an exhaust heat shield that is just touching when parts are cold?

 

[craiginuk]

what edd said. Mine used to rattle. The mounting had broken. After weld repair it is 100%

 

[chrisg]

Hallsy

there are a lot of heatshields and 'tin' bits on a turbo to rattle at any temperature, see comments on another post about an S2 rattle.

Rattles and also exhaust leaks are more prominent when cold ie outside the normal operating temperature. It could well be as Ed suggests that as the engine warms up and gaps open up/ close due to heat the rattle dissappears.

In my experience though if there's suddenly a noise/vibration and you've been driving the car for a while, it's not you being "paranoid or worrying..." its usually a sign that something has broken/slipped/ changed = don't ignore it, investigate it. If you ignore it or don't act it WILL come back and bite you eventually.

I found this recently and couldn't figure out what the rattle at tickover was - eventually traced to the Gearbox oil cooler mount bracket. If I'd left this for long enough, eventually the Oil cooler would have fractured, then sprayed oil everywhere and the box seized - or gone all over the rear tyres....

Chris (harbinger of doom..... [])

 

[scam75]

I snapped a cooler a while back, nothing seemed to end up under the rear wheels thankfully, then drove it about 10 miles back home, noisy box, feared the worst. Got a new cooler, filled it back up and perfect silence again! They are tough boxes!

Stuart

 

[Hallsy]

Yes - I suspect it is the exhaust that is touching the car as it sounds like it is down the right hand side of the car, more just a case of whether something is loose/broken, or a dodgy mount that is causing it.

Don't worry Chris, I'm not one to let problems persist - besides, I need to sort it out whilst it's still winter, as it only does it when it's really cold, lol!!