[f911g]

Hi everyone. I own a '99 996 that has developed an oil leak into the cooling system. At 98k mi. a beige colored sludge appeared in the coolant expansion tank.

At 63k the car had the head gaskets (HG), oil/water cooler, oil separator and several other parts replaced due to a bad HG.

My initial reaction to the sludge was the HG, but the engine idles and runs smoothly; no water in the engine oil, it maintains normal operating temperature, even in stop-n-go traffic and the engine does not smoke.

I replaced the oil/water cooler thinking it may have developed a leak and flushed the cooling system. The car was driven 1,1k mi. when a radiator vent hose blew just after the car was parked, at the same time I noticed a greater drop in oil level and increased sludge in the coolant expansion tank.

Could it be:
1. Another HG
2. Faulty Oil/Water Cooler
3. Possible oil/water mixing at Oil Separator
4. Another possible point of cross contamination?

I appreciate your feedback.