e30 piston rings or valve seal problem?

[[email protected] 0]

Hi there,

I have recently purchased my first e30 and absolutely love it!! It is a 1990 325i manual with 216Km and I would like to keep it runing in top condition.

Recently I have noticed a rough idle and slight knock in the engine only at idle it seems to go away with revs. My reseach indicated the ICV so I gave this a good clean as well as the complete air intake system, did not see any signs of damage and no change to idle.

I then checked the spark plugs, 5 of which looked normal but one had clean oil on the tip much to my horror!! My research suggests that it is either the head gasket, valve seals or piston rings. The oil looks fine so I can rule out the head gasket, I do not see any smoke when drivin so am hoping it is not the piston rings so I would like to explore the valve seals.

It seems it is possible to change the seals without having to remove the head, has anyone done this? I would rather not take it to a mechanic at this stage. I assume a compression test would tell me if it is the rings.

I appreciate any advice that you can give....Cheers.

[E30 325i Rag-Top 2957]

The biggest tell-tale sign for the valve guide seals is a big puff of blue/white smoke out the exhaust on start up. This is where the oil leaks past the seal onto the bottom of the valve and into the cylinders when stopped and is then burnt in the engine when it is fired up.

If you don't get the cloud of smoke on start up, it would suggest the problem lies elsewhere.

I have heard of other vehicles where you can replace the seals with the head on, but it usually involves special tools to compress the springs and an air supply to push the valve up when you want to put them back together. It's a bit more expensive to take the head off (new gaskets and bolts, etc.) but I would say it's a lot easier and you can clean the valves, etc at the same time.

[[email protected] 0]

The biggest tell-tale sign for the valve guide seals is a big puff of blue/white smoke out the exhaust on start up. This is where the oil leaks past the seal onto the bottom of the valve and into the cylinders when stopped and is then burnt in the engine when it is fired up.

If you don't get the cloud of smoke on start up, it would suggest the problem lies elsewhere.

I have heard of other vehicles where you can replace the seals with the head on, but it usually involves special tools to compress the springs and an air supply to push the valve up when you want to put them back together. It's a bit more expensive to take the head off (new gaskets and bolts, etc.) but I would say it's a lot easier and you can clean the valves, etc at the same time.

Thanks for the advice, just tried and there was no smoke and no smoke on revs either, may stil be warm (if this matters) as has only been sitting for a couple of hours, i will try again in the morning.

I have also read that drving down hill engine braking and then flooring it at the bottom will produce a puff of smoke indicating valve seal leaks. Should just go get a compression test I suppose, anyone know what these cost?