Hi, I have a 95 M3 with 127k miles. It overheated a little while ago and started burning coolant. I pulled the plugs tonight just to get take a look before I started taking the head off and noticed a lot of oil on the threads of the plugs but none on the electrodes. Also, there is what looks like oil residue in the throttle body. I'm hoping it's just a head gasket, any idea's or suggestions? Thanks Josh
I think a light oil residue in the throttle body is normal. You might want to check your oil to see if your coolant is going there - it has to be going someplace. I think if oil & coolant are mixing, it's supposed to look milky-brown on the dipstick (if the engine's been running & mixing them). Top off your coolant and pressurize your cooling system overnight; look for any visible leaks if the coolant level is low. If you don't see anything, pull the valve cover(s) and do it again, in case you might have a coolant leak or cracked head that could be spotted that way. If you dump in a bunch of coolant over multiple pressure tests and don't see any external leaks, it might be a good idea to change the oil and watch it drain - if the coolant is in the oil pan, then you'd obviously have a leaking head gasket, cracked cylinder head (somewhere), or, I presume less likely, some coolant passage issue somewhere in the block. If your cylinder head is cracked and you can't see/find it, changing the head gasket isn't a certain resolution of your coolant leak. Your head should be checked for trueness, you wouldn't want to put a warped head back on the car - find a good machine shop unless you're already one & can do it properly yourself. And, you wouldn't want to waste money machining a cracked head either - so check everything thoroughly before you get that far.
Well, I pressurized the system and found that it's leaking out the headgasket by cylinder 6, so I started the tear down today. Thanks for the help, I'll post on here once I find everything thats failed and finish the project. Josh
Sorry for the delay, I've been taking my sweet time getting this finished and just finally started it again on wednesday night. It sounds like it's running ok but at first it was pushing copious amounts of white smoke out the exhaust. I immediately thought that it was burning coolant but it smells like unburnt gas. When I parked it almost a year ago it had a quarter tank in it and I made sure to put a more than adequate amount of fuel stabilizer in it. It seems to have stopped producing the smoke at idle but will spit out a lttle at shigher RPM's. My dad has suggested that it's a combination of bad gas and the ecu trying to relearn the curve. What do you guys think ? Oh and before I replaced the head gasket I sent the head out to a local machine shop and had it pressure tested and the surfaced checked for warpiing and they said that they found neither. Thanks, Josh
The oil on the threads of the plugs (and any oil sitting in the spark plug holes) is probably a result of a leaking valve cover gasket. Both of my E36 M3's had the same issue. It got so bad on my '95 that when I pulled the plug on cylinder #1, the excess oil ran down into the cylinder so when I started it up, it smoked pretty bad for a while. Once I replaced the valve cover gasket, no more oil in the spark plug holes. Just my $.02...
Thanks for all the help, I ran out most of the old fuel and then put a little bit of VP 110 octane racing gas and it seems to be running significantly better. The little bit of smoke that it was producing seems to have stopped. Again thank you all for your help.
