1992 940 turbo rapping till up to temp

[petek153]

Having a rapping in engine hard to tell where exactly it's coming from but as it warms up it disappears seems to be getting worse as miles add up. Reminds me of how a diesel sounds when cold. Has about 145000 mi on it had something like it a few years ago was a bad exhaust gasket but in that case it never went away. I thought it might be one that was starting to go so I did replace but looked fine and noise is still there. Looking around the net some talk about piston slap which I've never heard of before. Any ideas out there ?

[James_A_Sousa]

Early Volvo turbos were built loose. You are probably hearing piston slap. As long as it quiets when the engine gets warm, you have little to worry about.

Our '90 744 TI did the same thing - I sold it with 230,000 miles, and I later saw the car with 275K on it.

Have a Volvo specialist listen to your car if you have any doubts.

I once met a man who was given a 740 turbo because the owner thought it was going to blow up - three years later the car sounded the same!

One thing that you should do is to allow the turbo to cool after it has been used at speed. The worst condition is to stop at a rest area after high RPMs and shut down immediately - especially at the top of a hill.

This can cause the oil in the turbo bearings to cook, causing damage.

Always allow your engine to run gently for 5 minutes after stressing the turbo - either driving without getting on the turbo, or letting it idle - this allows the oil to cool the turbo.