SigAlphAdam

Ohhhhh man...this reaaally sucks. For those of you who remember, last summer my car was overheating alot and i found out that the coolant was leaking into the oil. I posted the problem on rennlist, and got a variety of opinions.

The top three were:

1.) blown headgasket (most likely)
2.) blown oil cooler seal (maybe)
3.) cracked block (least likely)

I did a compression check, and got something like 150, 150, 60, 150, so i figured it was the head gasket. I ordered the new kit, and this saturday my brother and I went to work removing the head.

Well, after 8 hours of disassebly (including cutting off a few rusted & stripped bolts & nuts!), we discovered a PERFECTLY FINE HEAD GASKET!

My brother is saying cracked block, but I don't know what to do anymore! He's going to look into the oil cooler this week but if that's not it, I think i'm going to give up. I'm moving to the city in a week, and the 944 was going to be my "beater" car, just to get around with.

What do you guys think?

This site has always been alot of help to me, so thanks in advance for any advice.

Robert D

If it has overheated...perhaps something warped...like the head.

pete944

The low compression on #3 doesn't sound good. It could be a cracked block, a bent valve, or a broken ring.
The oil/coolant mixing still could be oil cooler seals.
Was the car burning oil?

Dave951M

Check your valves. A burned one can do that, as can a bent one. Easy way to test with the head off, place the head on a bench with the combustion chambers up, pour alcohol into each chamber and watch for anything flowing out the ports. Use alcohol because it has a very low surface tension and will flow out of very small cracks.

It could also be a broken ring on #3 causing it as well.

SigAlphAdam

No burning oil. Is there a way to check out the valve or ring since I basically have the entire head open?

jharding

Blown oil cooler seals send oil into the antifreeze first, resulting in a milkshake in the coolant recovery tank. A bent valve or broken ring answers the low compression problem, but not the antifreeze leak. You should still do a leakdown test to confirm if it is rings or not. It sounds more like a cracked head or cracked block.

peanut

A reading as low as 60psi is serious. Its likely to be a broken ring/s which should have been obvious because you would have had high crankcase pressure.
An easy test for broken rings is to put some light thin oil into the sparkplug hole and then re-test the compression. If the pressure increases significantly then it is broken rings If it doesn't then its likely to be a valve. Did you do this test ?
Alternatively it could be a sticking valve not quite seating properly on the compression stroke, or a piece burnt out of the valve edge but this would have shown up in the exhaust flow. Any mechanic could put his hand over the exhaust and tell if a valve was blowing by by the uneven pressure.

If the head gasket had gone between bore and waterway in the head you would have had significant white smoke on startup and when cold. You would also have been losing lots of water and hear gurgling in the heater hoses as they pressurized, Did you get this?
The test for head gasket gone is to do a leakdown test. A special liquid is put in the coolant and if carbon dioxide from the engine is getting into the coolant the liquid in your coolant changes colour . Did you do a leak down test ?


Check the valves and the valve seats carefully also look carefully into the waterways of the head for cracks/holes. Take your head to a engineering shop and they can do a pressure test and check if it needs skimming. Take your head gasket too so they can check that.

I don't think it will be a cracked block because you should be able to see water damage to one of the bores

I don't think it could have been oil and coolant mixing or you would have loads of emulsified oil which would be evident

I wish you had taken it to a local garage for a few tests before tearing it down. Now you have no way of knowing what was causing the overheating and can't do any tests now either.

peanut

not now you have removed the head there isn't which is why I originally advised you against removing the head until you had confirmed from testing what the problem was for sure

you're best bet now before you strip anything else and possibly lose any tell tales is to get a competant mechanic to check it over. He will be more likely to check and look for the right things in the right places.
best of luck

Dave951M

I think I posted the method for testing a head on the bench with valves still installed but being an old guy, maybe I was mistaken.

SigAlphAdam

should i just take in the upper half of the block that already I took off, or should I have the whole car towed to the mechanic?

peanut

it would be cheaper to have a mechanic come to you but make sure its an engine builder and not just a wrench monkey.

Yabo

if you have AAA or some other service, you should be able to get it towed for free..

peanut

yeah but you're going to have to pay to get it back again.

Bill

It is interesting to see how people tend to gravitate to the simple answer.

"The Head Gasket" has become the answer for all evils. Unfortunately in your case, this answer was not the simple answer.

Going back to when your gauge first indicated a problem, it could have been as simple as a failed overflow pressure cap ($12). If the cooling system does not pressurize, the coolant will boil. The more you overheat the engine the greater the chance of warping a head/loosing a headgasket/cracking a block. Or any other multitude of bad things.

Don't get me wrong, this forum can be helpfull. Just remember, there is no substitution for proper troubleshooting. Proper troubleshooting will save you a lot of money.

Danno

Hmm, something strange here... I've cracked all three rings on a single piston before and got some of the piston melted away and leaving a triangular hole on the edge. I still had 89psi compression in that cylinder compared to 140-145 for the others.

On NA cars, the oil-cooler seals are probably the main culprit in water-in-oil problems. The overheating 1st was most likely what did in the seals in the oil-cooler. This happened on Eyal's car recently. The overheating probably warped the head or fried an exhaust-valve, leading to the low-compression.

Things typically happen in a sequence of events progression. Most likely you've got a couple of problems to check out. Also take a close look at the thermostat and water-pump.