M42 overheating after head gasket
 

Hey guys, need some help with my motor. I have been trying for the past few weeks to get my car back on the road after a head gasket failure.

After all the work I've done, the car now starts right up and idles great. I can let it idle or even drive it, but eventually it will start overheating. The warmest it's gotten is to 3/4 on the gauge before I stopped it immediately. This has been only on trips around the block.

I've tried bleeding it at least 4 separate times at this point (using the instructions posted here, which include separate warm up and cool-down cycles on an incline), with and without water wetter. The coolant gets to a certain point, and just stays there.

Work Done So Far

• Head Gasket change (this included new gasket, stretch bolts, other gaskets, etc. that go along with this)
  • Head taken to a reputable shop. Head was not cracked or warped, but did need a valve job.

• New Water Pump and Thermostat (on my third thermostat at this point actually)

• All new cooling hoses under the intake (including the plastic piece from the block)

Things to Note

• The top coolant hose from the radiator to the thermostat is always hot, but the lower hose is cold. I tried removing the thermostat and running it, but it still wanted to overheat. With the stat out, the lower hose DID get much warmer.

• There is NO smoke, and from what I can tell no oil in the coolant, and no coolant in the oil. I have pulled the spark plugs a few times and each time the cylinders were clean.

• I did have a stripped water pump bolt that I had to helicoil, and I was not able to tighten it QUITE as tight as the other bolts, but close. No leaking from the water pump.

• There is a small amount of coolant coming out of the side of head/block directly above the plastic coolant piece and directly to the side of where one of the head bolts would be... this seems to leak only once the motor has gone to that 3/4 mark... until it gets to that point nothing leaks.

So off the top of your guys' heads... does this seem like a simple air trapping issue? A blockage in the coolant passages? Maybe the radiator? I'm honestly starting to get real stressed that maybe I cracked the block (perhaps I didn't manage to get all the liquid out of the head bolt holes?).

Any thoughts or advice from you guys would be great. I'm getting to the point where I'm about to call it a wash. :(

Did you use the correct head gasket? When you open the Rad cap is the coolant at the right level?

Thanks, John S

Well I DID use the Victor Reinz one... but I'd be quite surprised if it has already failed.

As for the coolant, it will bleed just fine to a point, and after that nothing else will get sucked into the system. The heat will be hot as all get out, but that lower hose just will not get warm.

where did you buy the plastic coolant pipe that is leaking.. depending on where you buy or if your lucky or not his might happen
http://318ti.org/forum/showpost.php?...3&postcount=49
so check that might be why your leaking... as for when your bleeding the system try massaging the hoses to help any air bubbles out.. did you clean the ports where both pipes go in.. gunk build up in the system? coolant gets pretty nasty when is mixed with oil and it dries

Yep got the OEM BMW one; measured it just to be safe before I installed it.

Did you get the head checked for flatness?

Yep, see my original post. :)

Really sounds like a bad head, or like you suggested a cracked block. Or the HG wasn't installed properly. If the head is leaking, you need to pull it off again.

Well I got the head off and sure enough it is now cracked.

SIGH

Man, that sucks- but I guess the upside is that you've diagnosed the problem! Is it cracked in a spot that can be repaired, or is it beyond that?

Not sure. My guess is no, but it can't hurt to see what it will cost if I can.