Sporadic Compression Losses - Engine Rebuilt

CherryHillPI · Post by **CherryHillPI** » 08 Oct 2009, 16:07

My mechanic is at a loss. After rebuilding my S80 he can not get a consistent compression reading on all five cylinders. It losses compression in different cylinders (each time or separate times) the car is started. He used two pieces of test equipment and confirms the readings are correct. Local Volvo mechanics are stumped.

Any suggestions? He's run all kinds of tests on the car but comes up with nothing.

Please help.

Post by **JDS60R** » 08 Oct 2009, 22:38

Can be worn valve guides or sticking rings. A leakdown test should be performed at each instance and the leak documented. Then repair all compression leaks.

Do not let the fact that it was rebuilt trick you into thinking something isn't wrong. Often a piston is not measured correctly and after honing the block the gap now allows leaks. The same goes for valve guide angles being off.

subdewd · Post by **subdewd** » 12 Oct 2009, 05:42

What's valve guide angles?
Wonder if the timing belt might be off a notch.