Help! Oil in coolant (but no coolant in oil). Possible causes?

Hello, I`ve got a problem, I discover oil mixed with water (like cream) in expansion tank. I know that is a bad news, I red in other posts this problem from other user (oil cooler, head, head gasket...) also associated with a overheating, white smoke,... But the problem is no water in oil, only oil in water. The oil level has decreased, of course, but my engine works perfectly, no overheat, no smoke. Please do you know in this case (only oil in water) what is the problem? Thanks for help.

AOS or a cracked head. When mine had the exact same symptom it was a cracked head.

Quotes source post: 15289131

Have you got water in oil (inside engine), or only oil in water (inside expansion tank)? And other problem like overheat or white smoke? AOS (Air Oil Separator) is a piece not related with this problem, maybe you confused with the oil cooler that is a radiator of oil in contact with coolant. ​​​​​

Based on my experience with intermix (which is no respecter to brands) is that you want to flush the system ASAP. Apparently, the chemical mixture of oil, petroleum, and coolant can be very damaging to the system over time causing serious deterioration of rubber hoses which then could cause blockages that are easily cleared. Therefore, don't wait around. If you have the light chocolate pudding looking mixture in your coolant expansion tank, then find someone to flush it properly. I believe I've read that Ahsai, PorscheTech3, Raby and other experts that comment of this forum recommend flushing it several times with hot water and shout.

Generally speaking, cracked head...

Quotes source post: 15289371

Yes, I know that is very important to flush the system, in fact, I have in mind to do it ASAP, but my real question is the origin of the oil-water mixing only in expansion tank and not inside engine. Can you identify, based on your experience, what element is associated with this problem? Head, oil cooler,... Thanks

Quotes source post: 15289545

Normally, intermix is commonly associated with cracks that are on the heads.The crack could also be located on the block. If it's definitely a crack that is causing the problem, then hope it's on the heads. Much cheaper costs associated with head service and replacement. I talked to enough people in the business of Porsches to know that it's NOT going to be a faulty gasket and it's extremely rare the oil cooler is causing the intermix. My bet is that it's a crack. Sorry. But don't let that stop you from doing the right thing. Cleanse the system of the milkshake and DON'T drive it!!! Tow it to someone one that has the knowledge and equipment to located the exact source of the intermix.

Quotes source post: 15289467

So, you can confirm me that oil in expasion tank is caused by cracked head. Remember that I havent overheat or white smoke, and inside the engine the oil is without water mixing. Thanks

Quotes source post: 15289655

"Confirm"??? Take the car to a mechanic for diagnosis if you want confirmation. Difficult to suggest what your problem is over the internet.

Quotes source post: 15289574

For me is very important to know when head cracked if the oil goes into expansion tank or the water goes inside engine. In my case the oil goes into expasion tank, and inside engine is without any water, and I know other opposite cases that water goes into engine.

Quotes source post: 15289663

I only want to know if a cracked head cause the oil inside expansion tank, not water inside engine. I am not talking in general oil-water mixing, I am talk specific mixing only in water cooling system (not inside engine)

Quotes source post: 15289663

Sorry for the confussion. Maybe restate the question... Do you know what case the oil goes into cooling system and what other case the water goes into engine?

You have to think of it this way - the engine oil pressure is much greater than the coolant system pressure, even when the car is warm and at any given point in time. So oil only migrates from the engine or engine component to the coolant system. Usually, if there is oil in the coolant it gets there one of two ways, cracked head or leaking oil cooler (the finned thing on back right of engine)....because there is oil and coolant in the oil cooler. The other case is coolant in the oil, and 9/10 times that is attributable to a broken diaphragm in the AOS. Now what you have to do next is have a compression and leakdown tests run on each cylinder. If those are okay, then the next step is to drop the engine and replace the oil cooler and O-rings. If the compression and leakdown tests are not okay, then you've got a cracked head.

Quotes source post: 15289663

Bingo! This guy wins the prize for the best advice. He's absolutely right. The only thing people on the forums can do is speculate based on the symptoms you share and hopefully lead you to make a responsible decision. Internet forum advice can NEVER take the place of an expert mechanic examining the car in person. Never! Listen, we're not talking cup holders or leather conditioning here. This kind of problem needs to be diagnosed by a professional. Many people that have intermix will save money and flush the coolant intermix themselves and then have the repair handled by pro shops.

Quotes source post: 15289732

How do you know there is no water inside the engine?

Quotes source post: 15290092

Sorry, but I think that is not correct. AOS (Air Oil Separator) separate the oil from the smoke that came from engine case, and enter only air in air intake. No water cooling related to the AOS or near it.

Quotes source post: 15290178

Because I have emptied the engine oil into a transparent drum and no see any water in the botton. Also the level of oil went down.

Quotes source post: 15290315

Ummmm...you need to look at the AOS system. I am correct, but you are entitled to think whatever you want.

Quotes source post: 15290365

I replaced the AOS last year, and I can tell you that is plastic piece with a membrane that connect the crankcase with manifold air intake. Only circulate smoke through it

So what you are saying is your AOS is unlike any other AOS in the world. Huh.....well here it is and yours does not have these lines attached? #12 and #13 are coolant lines designed to "heat" the AOS to aid in the separation of the oil mist from the crankcase, particularly in cold climates.

OP. What more do you want from the group? We have told you the most common reason for intermix (cracked head or oil cooler). The only person that will be able to confirm exactly what is wrong is a mechanic that knows these motors. I get you are asking about how there could be a one way leak, oil into coolant, and not vice versa, but this is very common across all cars. We can all guess at what it may be, but the internet is not going to magically solve this problem for you. If you want advice, here it is: 1. Flush the system (quickly) 2. Make an appointment at a mechanic 3. Take the car to the mechanic 4. Pray that it is the oil cooler and not a head Good luck. P.S. DB Joe is correct. Coolant does go through the AOS.

Sorry, you are correct the AOS has got coolant lines, I have a mistake, I change an AOS from other different car (boxster) and supose that 996 has got the same (like same block engine) The reason to asking about the leak only oil in water is because I red a long time ago in other forum that oil in water means a type of problem and water in oil means a different problem, and try to get an idea before start to dissasembly Of course the first thing to do is to flush the cooling system. Thanks for your help

Lots of advice and experts here, mostly on what they have been told, read here or heard. I will give you my view based on actual experience with this problem. In September of 2008, with 48,000 mile on my car the coolant light began flashing when my wife was driving the car. I had here drive it home and then looked at the coolant tank. The coolant was like pudding.Then I checked the oil and it was like a milkshake. So I had cross contamination both ways and it was severe.I drained the oil and replaced it and drained the coolant ( as much as possible at the drain plug) and replaced it. Then ran the car a bit and it was quickly cross contaminated again. If you check my posts you can read the whole story, I talked to mechanics, the dealer, etc. At the time I could not afford to replace the engine and most said that this was the only alternative. So I parked the car with cross contamination from that September until the next April, so about 7 months. Then I dropped the engine and found one of the most common cracks in a head. It was at cylinder #1 on the inner exhaust valve spring seat and extended down the spark plug tube. I can show you pictures of my head and several others from people who I worked with after I fixed my car and you would swear that they were all the same head, the cracks were almost exactly alike. In any case I had the head fixed and did the rest of the work myself and have had the car back on the road for 9+ years and another 48,000 miles and it runs great. So a couple of things. It is almost never a head gasket. Actually I have never heard of it being a hed gasket and never talked to anyone that had a head gasket fail. It is almost unheard of it being a oil cooler. I did test mine before I put the car away and the oil cooler was fine. A cracked head can lead to oil in the coolant and coolant in the oil, I know because this was the case in my car. When the car is running the oil is pressurized and this can force the oil through a crack into the cooling system. But when you turn the car off there is no oil pressure but the coolant is still highly pressurized (just try to take the coolant cap off the tank or a radiator while it is hot to see how much pressure there is) and can force coolant into the oil system. My AOS was fine, but I did replace it while the engine was out as it was 8 years old. My car sat for about 7 months with oil in the cooling system and I have driven it for another 9+ years and 48,000 and I have only replaced one or two hoses during that time. So it appears that the damage to the hoses from the oil was not so bad. I did spend a lost of time and effort flushing the coolant system but I can tell you that there were still traces of oil in the coolant for several years until the coolant had been replaced several times. So I am just relating what I experienced as opposed to what I heard, etc. I can also tell you that I have a brand new drivers side, 1-3 head that I bought after all this happened in case I would need it. If you are interested in the head let me know. Good luck.

Quotes source post: 15290767

Hello Dharm55, thanks for share your experience with your car. First of all I need to tell you that my car have been with this problem since 2 months ago, at the start of the summer when I checked the fluid levels, I discover in the expansion tank what I thought was a bit or dirt, I removed but never think that would be oil mixing, since few days ago that oppened the expansion tank and discover the horror. So my car was running about 2 months without any evidence of problem, no overheat, no coolant light, engine works perfectly. I think that 2 months is enough time to mixing oil-coolant in the 2 ways as you describe (oil pressure when engine is running and water pressure when stop engine), but against, my car only mixing oil-coolant in one way (inside cooling system). This is the reason why I'm asking if my car really has got a cranked head or maybe only the oil cooler affected (or a third part affected).

Quotes source post: 15290575

I think the coolant lines are there to prevent icing in cold climates.