91 318is overheated - hoping for the best, but fearing the worst

[lgb240]

My 91 318is overheated the other day (bonehead move by me, don't ask).

Once cooled, I went to add coolant, but, it seemed to leak out as fast as I was puring it in. The coolant seemed to be coming from somewhere behind the oil filter housing. I know that there's various coolant hoses under the manifold, but it doesn't seem to be originating from these.

I've begun the tear down, thermostat housing and water pump are out. Oil in the car is clean and clear, no signs of antifreeze. I can't see anything else externally. I don't want to pull the head if I don't have to.

Anything else I should be doing?

Thanks in advance...

lgb240

[strad]

Do a compression check. And I guess keep tearing it down until you find out where the leak is.

[mattdk318i]

IVe got a head if needed

[3bvert]

compression test
leak down test (a)
radiator tester thingy (b) ( IM tired)
a) if you dont have an "offical leak down tool" you can make one up yourself easy, cheap, not as accurate, but youll find leaks, and that for me is what counted
b) took an old radiator cap, fit a hose fitting into it, hooked it to my compressor, set the pressure really low , pumped air in. that test found a bad hose clamp

I bought a 91 318 wiht a know blown head gasket, it was a gamble, I lost

but no water was getting into the oil, it had cracked the head into an exsaust valve area, so the water was going into the exsaust and evaporating on its way out ( I guess).when it could, water was getting into the cylinder, like maybe when the engine ws off, but not much, and not into the oil

so at the time, I could not find a used head, the local machine shop welds up heads, so he did mine, nop problems yet. I lost, so instead of 150 for a full head set, I spent over 600+ getting head welded, and some new vlaves

hope you caught it early enough not to crack anything

[lgb240]

Compression test showed 200-203 across all 4 cylinders.

Ordered a water pump and thermostat today. Hopefully that's all I need.

lgb240

[CCR Engineering]

If it was behind the oil filter housing its probably that crappy plastic pipe that goes down the side of the block.

[Cobra Jet]

If it was behind the oil filter housing its probably that crappy plastic pipe that goes down the side of the block.

EXACTLY. It's called the "coolant bypass pipe" or on realoem - "connector". This is attached to the head on the driver's side directly located behind the oil can assembly. These are known and prone to cracking and/or leaking due to age and of course years of underhood temps.

DO NOT replace this part w/ an aftermarket "cheap" part or by a company called "URO". Do yourself a BIG FAVOR and go to your local BMW Dealer and buy this part directly from the Dealer, you should not pay any more than $30 for the part. The aftermarket parts are made poorly and are also known to fail shortly after the installation of them....

Read the below thread for exacting & factual info on this part:

http://www.m42club.com/forums/showthread.php?t=7574

Also, if your M42 is original and you still have a medusa of rubber hoses under the intake, I highly recommend that you do read and follow through w/ the "deletion" thread below that is used by many of us M42 owners... It will surely save you any future headaches and also $$$$$.

http://www.m42club.com/forums/showthread.php?t=2742

One more thing - how long did you drive it while it had already reached critical temperature overheating? I would be concerned that there could have been damage done to the head. M42 heads are FRAGILE when it comes down to any type of overheating issues. Cracks can form and are very small - you won't see these until you pull the head and look over the bottom side. Head warpage is another issue of concern IF you drove it for some time while it was overheating. If you pulled off immediately upon seeing the problem - you may just be one of the lucky ones as far as saving the head from damages...

Check all of the hoses under the intake for any other lose clamps and or cracks in the hoses - they don't last forever.