Engine ran overheated, lost alot of oil and now no compression

I recently bought a 2000 328i from a friend who overheated the car when the accessory belt on the water pump failed. He kept driving the car for several miles with the temp gauge in the red and it eventually lost all power. He had it towed to a shop and they said it needed a head gasket and a new head, quoting him $5000 for the fix.

So he ended up selling the car to me for next to nothing, and I began pulling it apart to see if I could get lucky and just change the head gasket and be good to go.

I believe the car does have a bad head gasket but am worried it might have sustained damage to the bottom end. These are the symptoms I have found so far:

Car was very low on oil, like not even on the dipstick. I drained out about 3 quarts I believe and this was within 1000 miles of an oil change and he is confident it was full of oil before it overheated. It appears to have blown a lot of oil out on the drivers side of the engine but I cant tell from where. The oil has a strange, acrid burnt smell. The oil does not appear milky or have any other signs of coolant in it.

The coolant appears to be full and I can't see any signs of oil in it.

Spark plugs looked flooded with fuel, probably from trying to start it. They may have had a little oil on them.

Compression is way low; I only checked two cylinders but one was only building 40psi and the other maybe 10.

Anyone have any idea if I might get away with just changing the head gasket or does it sound like I have bigger problems?

I have the Bently service manual and am familiar with checking the head bolts to make sure they will take torque and the threads in the block aren't damaged before removing the head.

Any input is appreciated!

Pull it apart. Head goes to machine shop, block gets checked with a straigthedge to see if it's warped. My guess is that it is. General MO from what I've read is to helicoil/timesert the aluminum blocks, regardless of whether the threads are intact.

The smell in the oil is probably the by-products of combustion. I would guess the coolant smells that way too.

Honestly, you're probably best off sourcing a junkyard engine from a totaled car.

junk yard engine would be my suggestion as well, and then also get new cooling system parts, belts, tensioners, etc because im sure if the belt snapped in the first place, it wasnt well maintained.

^+1. Junk yard engine is a cheaper solution than a head job, its also more likely to last.

I atleast want to pull the head off and check things out.

Do you need the special BMW service tools to remove the head or just to reassemble? And can anyone recommend a place that rents out the tools for reinstallation?

Junkyard engine.

replace the engine.

I went through the same exact thing last year. bought an 02 vert that had been overheated. So glad I just replaced the motor and was done with it. No special tools needed, fix a lot of other stuff while you're at it.

She's toast. New car time.

Drop in a new motor, cheapest solution.

Originally Posted by Valkyn

I atleast want to pull the head off and check things out.

Do you need the special BMW service tools to remove the head or just to reassemble? And can anyone recommend a place that rents out the tools for reinstallation?

http://ezflatscreen.com/carpages/m52headremoval.php

This DIY mentions a guy who has them, you might search around. I'm sure someone out there has them, and rents them. Pretty sure they're just for cam/VANOS timing upon reassembly.

You don't necessarily need another engine, but if the block is warped, it would likely be cheaper.

Junkyard engine. The block won't take bolt torque and is toast let alone the head.

Engine can be repaired. Same thing happened to the PO of my car. Block was fine. timeserted, decked the head to level it back out, block was not warped. Rebuilt and running like a champ now. PO said he spent around 2-3 grand with all the "while you're in there" type of replacements.

=1 on junkyard motor. A heavily overheated E46 motor is a boat anchor, plain and simple.

The thing many seem to miss on a severely overheated engine and one that was also very low on oil would be cylinder wall integrity and the possibility of broken piston rings.

Just because the cylinder walls may look fine, does not mean the piston rings may have expanded enough to close the gap, then they are likely to break in one or more locations. This is when you end up with questionable compression.

With as many of these cars around, I am sure you can find a reasonably good shape engine out of a wrecked car for a decent price.

It will save you loads of time waiting on the machine shop, may even be cheaper than a head job??

Sort the VANOS seal, oil filter housing gasket, CCV and all the typical problems when you swap the engine. Then you will be golden for quite a while.

Originally Posted by Scooby24

Engine can be repaired. Same thing happened to the PO of my car. Block was fine. timeserted, decked the head to level it back out, block was not warped. Rebuilt and running like a champ now. PO said he spent around 2-3 grand with all the "while you're in there" type of replacements.

Yours wasn't 'heavily overheated' then. When they are the aluminium block is junk.

I'm definitely going to pull the head and see what's up. How do you identify if the block is junk or not? just by doing the head bolt torque test and inspecting the block for flatness/cracks?

Originally Posted by sprintman

Yours wasn't 'heavily overheated' then. When they are the aluminium block is junk.

I would consider running dry on coolant, then having the head warp enough to lose the head gasket heavily overheated. Can't imagine it overheating much more considering the car was no longer driveable...no more damage to be done.

Head warped, block didn't. Even with all aluminum long blocks, in my experience, the heads will tend to warp easier than the block, as seemed the case with my car.

However, in this instance with such a rapid loss of oil and multiple cylinders with low compression, can't know for sure until he tears into it. It's certainly worth a look though. Less than a day's worth of work if you know your way around a wrench.

Originally Posted by Valkyn

I'm definitely going to pull the head and see what's up. How do you identify if the block is junk or not? just by doing the head bolt torque test and inspecting the block for flatness/cracks?

What do you mean, head bolt torque test? Like I said, you will want to timesert or risk having to repeat the job. It'd be foolish to skip this step.

The only way I know of to test the rings is to do a compression test once you have everything back together. There is no test for the bearings themselves afaik. The solution would be a rebuild. :/ Without knowing how far your friend went, and how low on oil, we can only speculate. There's a reason you are supposed to pull over and turn the car off immediately.

Originally Posted by lcoleman

What do you mean, head bolt torque test? Like I said, you will want to timesert or risk having to repeat the job. It'd be foolish to skip this step.

The only way I know of to test the rings is to do a compression test once you have everything back together. There is no test for the bearings themselves afaik. The solution would be a rebuild. :/ Without knowing how far your friend went, and how low on oil, we can only speculate. There's a reason you are supposed to pull over and turn the car off immediately.

Although I agree that timeserting would be prudent if reusing the block, BMW themselves talk of a "head bolt torque test." See the attached TSB.

OP, I applaud your desire to tear into the current engine. Assuming you aren't on too tight a schedule, this should be a good exercise - with the slight possibility of saving the current engine. However, if the motor overheated and lost oil, you easily could have bearing damage, or other goodies that will make this endeavor moot. Just be prepared

Good luck!

Luke