2002 H6 - no compression!

21931 Views 59 Replies 11 Participants Last post by Novablue, Nov 19, 2012

FFR5445

Discussion Starter · Nov 6, 2012

Hey guys. I'm hoping you can help me out. I have a 2002 LL Bean with the H6 engine. Went to start it this morning and it just cranked over fast, no start. If you've ever heard an engine trying to start with a broken timing belt, that is what it sounds like. I verified fuel, then spark and both are good. Plugged in my compression tester to the RH middle cylinder and I get zero compression. I don't even want to bother checking the other cylinders because they are such a PITA to get to and I'm fairly certain they all have zero compression also. So what the heck happened here?!? It has about 160k on it and car was running great last night.

My next thought is to pull the timing cover and start checking it out. I'm guessing I have a broken timing chain or stripped timing cog.

Does anyone know where I can find a guide on pulling the cover? I assume I just need to pull the radiator and then I can get at everything?

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Novablue

· #16 · Nov 7, 2012 (Edited)

Zero compression usually means one of a few things namely:

Valve issue

Piston issue

If when performing a leak down test the compression rises significantly it is a piston issue. If it stays the same it is a valve issue. I don't know your engine specs but 5-10% difference can be normal, more than that is bad.

If you have oil coming out the tailpipe, you likely did the leak down test incorrectly or your engine is toast. Rotten eggs is a tell tale smell of a blown engine btw. You only need a small amount of oil to perform the test. If you are confident you did the test correctly you may have a broken crankshaft. It is really rare to have zero compression in more than one cylinder on both sides of the engine and have it be a piston issue. What you are describing sounds like the valves are not sealing correctly.

Of Course if you have a broken crank, nothing would line up right and the valves would be open when you do the tests. Lets hope it's something simple. It sounds bad at the moment. If a pulley went bad or the chain/belt was loose or broken you might experience what you are describing.

If it were me:
Perform a compression test on all cylinders. If all cylinders are zero it is likely a valve or crank issue.
A) Compression is zero on all cylinders, most likely a valve issue: a) double verify timing belt is correct b) Verify that the crank is in the proper alignment which is more difficult.
B) Compression is good on other cylinders but not the two: Suspect bent valves on bad cylinders

From here we could check more but I'd need to know the results of that to proceed.

My first guess without seeing it is the chain/belt/pulley broke.

Edit: Also make sure you are using the correct threads for your compression tester. Line them up with the spark plugs to be sure.

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Novablue

· #18 · Nov 7, 2012

1 Lucky Texan said:
if you have any doubt about the compressions tests, check for the cracked cap/blown o-ring on the fuel pump.

(I'd like to see a picture of how you do a compression test on this engine, especially cyl #6 !)

What does the fuel pump have to do with cylinder compression?

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Novablue

· #27 · Nov 8, 2012

Have you checked to see that the chain actually moves properly when you crank the engine? Broken chain is still my top suspect.

The oil change thing you described sounds interesting. Could be a failing pump or sludge.

I agree with Cardoc (he is the greater expert than me anyway

), you are headed for a new engine. While I believe what you are saying it sounds unbelievable.

It's worth pulling it out the rest of the way just to make sure at this point.

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Novablue

· #42 · Nov 11, 2012 (Edited)

FFR5445 said:
The cylinder head is off. No bent valves, no holes anywhere. At first I was all upset because nothing was obvious and this is just so strange. But then I took a closer look. LOTS of carbon build up on cylinder and around valve and valve seat.

What do you guys think? Did I figure it out, or did I take apart my wife's car for nothing!?!?!?

No you didn't.

Take the heads to a shop that specializes in cleaning and machining. Not sure about the block because you didn't show picts of that.

This engine shows poor maintenance over it's life possibly cheap fuel and lack of cleaning. Once it's cleaned up I think you'll be happy assuming nothing is bent which is why you should have it checked out. It's possible to not "see" a bent valve. Get estimates and see if you want to go new or clean/repair.

Carbon build up causing no compression is possible in situations like this.

I agree with Cardoc. Other manufacture engines would not be worth repairing at this point because there would be more damage.

As to using sea foam, it works if you use it like Cardoc says, but I have had good luck by trying to make sure I always use premium fuel. I've put 100k on 3 engines now and all of them look like new with those miles. I have yet to use sea foam but I do use good synthetic oil and Chevron or Texaco fuel. "An ounce of prevention is worth a pound of cure."

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Novablue

· #46 · Nov 11, 2012

cardoc said:
The PCV system allows the engine to pull gases out of the crankcase that are created normally from heat and pressure. At the same time it sucks oil particulates. The particulates adhere to the surfaces of the induction system and over time will thicken. This changes the flow of air. It adheres to the intake valves as well as the oil is pulled through to the combustion chamber. This is that black film you often see on the trottle body. When crankcase pressures are high during high engine rpm, the effect is greater.

Abnormally high crankcase pressure can be due to small things like using heavy oils to ring blowby.

On this engine it appears the valve seals are bad. When the engine is stopped, valves remain open. The oil deposit at the base of the head indicates the oil was draining into the head every time the engine was stopped and the next time it was started it probably smoked a bit until it burned off the loose oil in the chamber. Judging from the photo it looks to have been going on a while. It just got to the point the carbon and sludge lodged the valves open.

It is possible that a clogged PCV valve could accelerate internal leaks. The pressure will find a way out. Given the mileage of his engine, the seals were most likely worn.

It may sound redundant but I second this post. :29:

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Novablue

· #60 · Nov 19, 2012

:roadtrip:

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