Recurrent intermix, any ideas?

[sehorntx]

99 C2 with prior cracked heads. Removed heads, had them repaired. Car ran great until recently noted recurrent coolant emulsification in the oil. This time only have coolant in oil and no oil in coolant (perfectly clean). Preparing to drop engine again and look for recurrent head cracks. Any ideas? Had new oil cooler put in by indy before figuring out the real problem myself with the help of Dharn55.

[wvicary]

Are you sure it's coolant in the oil and not just normal condensation from the combustion process?

[logray]

+1 to above, do you mean what's on the underside your filler cap?

I've seen a little of this in my AOS and also on the oil filler cap, but it's not coolant (as proved by UOA). Best way to clear that out are some "spirited drives".

Did you have the oil tested (i.e. blackstone) to see if there really is coolant in it? (before pulling the heads again).

[jsoderbe]

Did you have a reputable shop repair the heads? From what I understand they need to cut out a pretty big piece and start repairing from the inside out. They cant just weld the superficial crack. At least that is my understanding.

I am definately no expert, but there shold not be coolant in oil without oil in coolant. Reason is that the oil pressure is higher than coolant pressure. Of course, when the crack is big enough there will be intermix, but that is intermix both ways.

However, coolant pressure should be higher than oil pressure when engine is turned off hot, but you should still have oil in coolant.

Even though it does sound unlikely that you should have another non-related problem at the same time, I should at least check for other reasons before I pull the engine again.

Thanks,

Johan

[sehorntx]

Thanks for replies, definitely have coolant in oil. Kept losing coolant (warning light flashing). And when I drained oil it was clearly badly contaminated. I agree dont quite get why no oil in coolant. Gonna pull heads and have them repaired. also will throw in a new oil cooler for good measure. Thankfully its winter in Texas and good work time in my garage.

[txhokie4life]

You could have a crack in the cylinder liner that opens up when the chamber gets hot

and coolant enters the chamber and some gets burned off -- but when car sits, coolant leaks back into

chamber -- then down cylinder walls into the oil.

Do you have any misfires?

Any coolant in the cylinders or evidence on plugs?

If you do have this scenario -- you really don't want to be driving it as this is the start of the infamous d-chunk failure.

Mike

[logray]

You can also boroscope the cylinders per MIke's comment to inspect and read what you're in for before going to far into a repair... definitely pull the plugs and read those too. Would be a lot of money wasted to pull the heads if they don't need repairing, only to find the case has been compromised... in which case it's big decision time on what to do next.

[txhokie4life]

To give you an idea -- my partner had a customer with a 04 996 that would misfire at start-up but then run fine.

It was a cracked liner --- maybe 1" in length, but deep enough (or wide enough) to catch your finger nail.

The owner had the cylinder boroscoped and saw the coolant, but never saw the crack.

We didn't boroscope that one, but found the crack upon disassembly.

Customer chose to bore out to 3.8 using LN Engineerings Nickies.

Wasn't cheap.

Mike

[sehorntx]

I have engine ready to drop. Once down will pull plugs and scope the cylinders. if coolant pooling found will have decision to make as you have pointed out. Will keep you posted.