Yellow sludge and Thermostat
 

Question. I know the yellow sludge is probably from condensation in the oil, but i just rebuilt the head on this M54 3.0. I had changed the oil as there was obviously coolant and other cleaning chemicals in it, but i'm not sure if some possibly stayed back as i like doing my oil changes when the engine is hot to make all the oil run down.
I noticed that my temp gauge takes a while to get to 12 o'clock but its also been averaging -5 to -10 Celsius the past couple weeks. I swear my old 99 e46 m54 engine could get to 12 o'clock just off idling. This thing doesn't leave the blue on idle but if i drive it, it gets there and stays.
I also don't shut it off until it stays at 12 o'clock for a bit. I know these motors don't like short trips in the cold.
I'm guessing the thermostat is slightly open and may also be the culprit! (yes i should have changed it when i had the head off, but it had looked brand new.)

Thoughts??

Common in the winter months and I see you are from the "great white north". Just get out there and drive it for an hour or 2 and she should clean right up. Be watchful for the CCV failure causing hydrolock once that tube freezes up.

Yeah starting seeing more posts through the day saying the same. i put a brand new CCV with the "winter coat" on it recently. i think my son was taking it on short trips last week.

I told him and the wife, don't shut the truck off on cold days until the temp gets to half. I remember this from my old e46 323i. i cleaned it also checked the temp in case of a thermostat issue and it stays between 93 - 97 Celsius.

Gonna drive it for a couple long trips to make sure! thanks!

That's really all you can do. Most people don't even do that so you are way ahead of the game. Just avoid the short trips in her for now and remember, spring is right around the corner. :thumbup:

Thanks for the posts. Just to clarify for all readers:

1) the yellow sludge is a mixture of oil and water

2) the sludge turns back into oil when the water is boiled off and the steam is sucked into the ccv system for disposal

3) the water in the oil can come from condensation of blow by gasses from combustion. ie: gasses escaping past the piston rings have small amount of water.

4) condensation becomes a problem on short trips in cold climates. The oil never heats up enough to purge the water.

5) it can eventually lead to a hydrolock and engine destruction.

Thanks for the reminder warning!

:bustingupYou have me scared!! Lol. Did a few long trips. Hopes this helps me out !

I've worked (extensively am sorry to say!) on an M54 in my GF's E46 325. Same engine save for capacity I think. I recall when researching how to change the CCV that there is a cold climate CCV and set of evaporation hoses - are these fitted to your car?? Essentially the CCV is smaller and thicker plastic I think - and the hoses are lagged in foam.

Yep, the Cheese Wiz in Wintertime in Northern climates is normal. Been thru that and had the Oil Separator freeze up and smoked the ENTIRE neighborhood which sent the fire trucks and other first responders. Obviously, there was no fire, just a frozen oil separator and a $2K repair bill. Try to drive the truck on longer trips and Spring is just around the corner, the Cheese Wiz will go away.

It’s warming up a bit and did more long trips. It’s almost gone! Plus I did a new CCV about 3 months ago when I first got the truck. I’ve installed a few on Other m54 motors and all cane with the “winter coats” around the hoses and units. I’ve been doing some extensive reading and watching vids of hydro lock and ccv failures and now fully understand how this system works on the M54 motors and why they fail. I had my last 323i 99 for about Half a million km and never changed the unit once but I drove that car hard and it always heated up nicely. Not sure how the ccv lasted so long ?!?!?!

Your guess may be right. Replacing the thermostat completely eliminated green sludge issues on my 85 X5 3.0. The engine had just turned 100K. The thermostat ages over time to negative failure mode, opening too far for the ambient temperature. I immediately noticed warmer air from my heater when cold outside. Running at the right engine temperature also improved performance and gas mileage too.