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jc · Joined: 22 Apr 2003 Posts: 864 Location: Cleveland, OH

Flooding the engine can result in severe loss of compression, however this is not likely to happen while the engine is running (as in the original post). You usually will notice a very strong fuel smell also. DPK - did you find out what the problem was?

BimmerBryan · Joined: 08 Dec 2004 Posts: 18 Location: Louisville, KY USA

Come on....If there is a loss of compression on ALL six cylinders, how can it be anything but a cam not moving, hence a timing gear or chain? I agree that there should be ONE or more with high compression, so I too am wondering if the shop knows what the heck they are doing. I've never seen "valve sludge" that can do this...This is an interesting situation. I believe that some of the said variables in this equation are not adding up. Hmmm....

johnnyrat · Joined: 12 May 2005 Posts: 4 Location: Atlanta

quote:
Originally posted by dpk1000:
ZERO compression-with the others really about 30 lbs. ?

A similar thing has happened to me twice. Although not while the car was running. It was running great turned it off and tried starting the car later ... once was the next morning with it very cold ... maybe 15f the other was last week (July in Atlanta) and the car was still warm. My mechanic says that gasoline runs down the cylinder walls dissolving the oil layer and causing the cylinder to lose compression. He removes the spark plugs and injects a little oil in the cylinders puts the plugs back in and it will fire up. He tells me he has seen this with other BMWs. It would be nice to know the root cause of this.

MD. · Joined: 17 Jun 2004 Posts: 338 Location: Holland

It's good to hear Your problem is solved.

It is a very strange thing though.

When just one cylinder has 0 compression it's usualy somethign very bad.

With broken head gasket mostly it shows some compression. With compression going arround psiton rigs it should still have some compression. Also thermic laws say such a thing is imposible. Well metal parts (pistons and piston rings) expand on heat. Hence piston rings grow hence compression on warm enigne is higher then with cold engine.
Also when Vanos fails then most of a cylinders had problems not only one.

Only problems I know of that can cause one cylinder to fial compression drasticly to a 0 are valve train/ head problems.

Like stucked valve can cause it. Broken of valve or part of a valve can cause it. Dirth in valve seatings can cause it (carbon build up) Carbon buildup anywhere arround valves can make it.
I've seen exhaust valves of a 7 years old engine that was driven allways only up to a half of it's rpms and belive me there was a 1/4" thick layer of carbon buildup on it.
It caused valve failure (valve broke) and engine hardly survived.

When I hear this story it sounds to me like oil helped valve to start moving corretly again. Though it could be I'm wrong.
But in any case I would go and hot soak engine and change oil and oil filter and I would run next few tanks with injection cleaner fuel aditives and better fuel.
I would mostprobobly or clean and check out a gap of spark plugs or change spark plugs.
I would also connect ODB reader and see eeror codes. I would also check engine timings to.

Good luck

[ 08-04-2005: Message edited by: MD328E36 ]

gigel · Joined: 12 Sep 2002 Posts: 1533 Location: Dallas/TX

I thought about this and the only explantion to me is valve being stuck open. Oil might help move it again. As MD said.
While the oil in the cylinders can increase compression when rings are bad, there's no way it can "restore" compression from 0. The rings are "sealing" the piston, not the oil. This is my only logical explanation.

johnnyrat · Joined: 12 May 2005 Posts: 4 Location: Atlanta

quote:
Originally posted by Cristian:
I thought about this and the only explantion to me is valve being stuck open. Oil might help move it again. As MD said.
While the oil in the cylinders can increase compression when rings are bad, there's no way it can "restore" compression from 0. The rings are "sealing" the piston, not the oil. This is my only logical explanation.

Seems like if a single valve was stuck the engine would probably start or at least try to. When I experienced my problems there was nothing ... not a hint of combustion. Am I wrong?

cmcon98 · Joined: 13 Nov 2002 Posts: 1844 Location: Boston

Assuming the compression test was accurate, I'm guessing one of the timing chains slipped or failed, causing pistons to bend valves on some cylinders. If this is the case, and there's no other collateral damage, you can pull the head and exchange it for a rebuilt one, install it with a new head gasket and new timing chains, sprockets, and tensioners, and you should be OK. This may not be worth the cost if the rest of the car is not in good shape.