Cracked head or bad head gasket?

[Balleristic31]

Symptoms:
On cold mornings the car shoots a little white smoke, and develops a fair amount of froth on the oil cap and dipstick. And will run rough on start up. This is after not running the car all night.

What makes me curious is that when letting the car sit for 6+ hours during above 75+ degree outside temps, the car will start great, have no froth on either dipstick or cap, and not smoke or smell of coolant in any way.

I did a compression test a bit ago but will redo it just to double check, but my gut says cracked head allowing coolant into the combustion chamber when the metal hasn't expanded yet. But that doesn't fully explain why it runs great in warmer weather. Any ideas?

[bmwman91]

Does the white smoke smell like coolant? A little bit of water vapor is perfectly normal on cold mornings, until the engine warms up. Rough starts and such can often be from a dirty ICV that is gummed up with condensed oil vapor.

The only real indication of a problem is that you have gunk in the oil. If you do a lot of short drives where the thing does not warm up all the way, MAYBE you are lucky and it is just condensation in the oil that doesn't evaporate.

I'd bet on a bad HG, if there is a problem. The head most commonly cracks around an exhaust valve guide at cylinder #2. If that was the case, you would get white smoke on hot starts too since coolant would be draining into the exhaust once the exhaust back pressure drops. You would also be losing coolant and finding a lot of air in the system.

[Balleristic31]

The white smoke is definitely coolant, smells like it and all. I am loosing a bit of coolant on the cold mornings but not like emptying the system. I just redid the water pump about a week ago and the car bled coolant normally, and does not overheat at all.

[bmwman91]

Hm, yeah burning it definitely says head crack. Has the engine ever overheated that you know of? The M42 head is somewhat notorious for cracking around the exhaust valves when it overheats.

[roguetoaster]

Probably a crack in the head, but you won't know one way or the other until you pull it. Best of luck.

[Balleristic31]

Engine definitely overheated before I owned the car. Looks like I'm pulling the head :roll: