Oil / coolant mix on 2000 996

HELP HELP HELP. Novice 996 owner just got the kick in the ******* call from mechanic.........oil in coolant, coolant in oil. Auto is currently at Eruopean performance in Raleigh [by fairgrounds]. I need any and all information folks have concerning options. Initial estimates for work are very high. Auto is a 2000 996 with I believe a 3.4 L. Thanks Ed S

Damn, so sorry to hear this. My first call would be to Flat 6 Innovations for a phone consult. Jake can certainly tell you what your best options are.

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While I have no direct experience with Porsche engine rebuilds, generally an engine rebuild is an expensive job. It can be extremely expensive if the wrong shop is chosen to do the job. IIRC the 2000 MY cars came with a 3.6L engine. If not, if the engine is a 3.4l engine, well of course you can replace the engine with a 3.4L sourced from another car. The risk is the replacement engine could be sick. Ideally you and your best mechanic would want to hear the engine run before you buy it. You can install a larger (3.6L) engine. You could still get a bad engine. Also, there are some issues with installing an engine from a newer MY into an older MY car but the issues have all been resolved Imm sure.

Search terms: intermix, AOS, cracked head. With some luck, Doug/Dharn55 will impart some words of wisdom from his experience. GL with solution.

How many miles on engine ? How often was oil changed ? While there are a few possible causes here .. Search d-chunk. Seems to be a problem on some 3.4l engines due to weakness induced in casting process. Temp cycling the metal will eventually cause big crack. New engine is probably on the order of 16-20k .. At that point the car may not be worth much more. You could try and find a wreck where the engine is good .. But even that is probably 8k plus and the 3.4 can still be susceptible to the same problems. Some said early '99 motors were cast in different factory and didn't have same issue .. Not sure about rebuild options .. But yes talk to flat six. Not sure what the car is worth without e fine .. But sat $5k .. You might consider just upgrading to a 2002 -2004 with ims done ... Probably similar cost to a rebuild ... Good luck .. Hopefully this is not the worst case scenario

Happened to my '99 C2, @ 4 years out of warranty. With lots of work, persistence and help from the dealer Porsche NA good willed a new updated motor. I paid for coolant and the dealer's labor to install. Your options are a fairly expensive repair, chancing on a used motor install, a new reman motor from a P dealer if still available but very expensive. GL

Send it to Flat 6 Innovations. Stay away from your local Porsche dealership. They know **** about these engines. I'm experiencing the same issue you are with my '99 911 and sending it there.

The intermix issue could be something as simple as the engine oil cooler corroded and allowing the two liquids to mix. Fingers crossed its something simple but more often than not its going to cost. A 3.6 engine option may not be compatible swap from a 3.4 due to E-Gas depending on year.

If both the coolant and the oil have intermix I would get a leakdown test done and the AOS checked first.

There's no coolant in the Air/Oil Separator.

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There is coolant in the AOS.

Infra, just to clarify, they are referring to the oil vapor separator (which has coolant flow) on the top left rear of engine not the AOS system in the sump. The "AOS" acronym is sometimes used to refer to either system.

what were the symptoms that had you take the car to the shop

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A year ago, I had a major coolant leak. Thought it was the water pump. It was the AOS.

Hopefully just this.

Hopefully just this.

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Maybe a Trans Atlantic parts translation problem.

well trust me when I say this there is realy no easy fix for the intermix issue. I went through this with my 2000 996 and my biggest mistake was not getting it rebuilt from the beginning. I had several shops tell me if you had water in the block you might as well just rebuild it but i was destin to find a cheaper solution and i ended up paying for tests, oil heat exchangers, multiple oil changes and flushes and then I was told that I had a porous block so the engine was non rebuildable and all it ended up being was a cracked head. They was a compression test, leack down and it did not show up how ever when running it would intermix oil into the coolant and coolant into the oil. IF, and i say IF you caught the intermix early (how can you know for sure unless you check the oil and coolant evry couple of days) well you can just flush it out repait the head and keep on going. But I did n't want to pull and engine, fix a head, reinstall and then later find out that my bearings give out because they were ran to long with water in the case. a basic rebuild will be about 7500-9500 if you only have a shop drop engine pull the heads and have the head fixed you may only be looking at 2500-3500 I ended up going from just doing a basic rebuild in the fall of last year, to lets do a big bore/stroker with high compression ratio to now doing a turbo charged big bore stroker with low compression ratio on e-85 fuel LOL

Have someone that knows these engines well do a proper diagnosis first then decided what to do.

OK I will jump in now having suffered and fixed an intermix. Talking with Flat 6 is not a bad idea and I have great respect for Jake Raby. The challenge is that the best option if cost is not an issue will be a Flat 6 engine, there probably are no better engines out there. However they start at over $18,000 and quickly go up from there, plus you have to transport the car there and back. So we are talking about spending $20,000+++ to put an engine is a car that is worth about $20,000 and won't be worth that much more when the work is done. For many people that just does not make sense. I think jake is also fixing cracked heads now, but it is still expensive with the shipping, etc., and probably not his recommended approach. Probably the first thing to do is to determine what the source of the intermix is. You can check the oil cooler, they can crack and I certainly checked mine, but it is almost never the source of the problem. As for the AOS, I guess it could cause a intermix, but I have never heard of this being the source of this kind of a problem. It could be a D chunk and you might see this with a boroscope, or by taking the head(s) off but I think the most common source of this problem is a cracked head. If you check the threads on my repair you will see lots of information and pictures. It is probably a crack at the inner exhaust valve spring seat on cylinder #1 or # 6, mostly likely #1. If you remove the engine and the cam cover, cams and lifter body you can usually see the crack, start with the 1-3 head. These cracks can usually be fixed. I spent $500 including a valve job on that head, but that was a few years ago so the price is probably higher now. I also have a new in the box 1-3 head that I will sell for $1,600, at the dealer they are over $3,000. It took me about 40 hours or so to do the work, and this was in my garage with no prior experience on the M96 engine. If I had to do it again I would guess about $15-20 hours. You need some special tools, either make them or buy a set. I can also rent you the tools you need. I spent another $800+ on parts directly related to the crack, and more to replace other things while I was in there (coils, plugs, tubes, AOS,etc.). Now some question whether an engine with intermix can be saved or is worth saving due to damage to bearings etc. I will tell you that my intermix was really bad. The coolant was the consistency of pudding, and the oil was like a milkshake, and I don't know how long it was like this. I discovered the problem when the coolant light started flashing. And when this happened in 1998 the dealer,my Indy and Jake all told me had no choice but to put in a new engine. At that time Jake said that cracked heads could not be fixed, but now we all know that in many cases they can be. I am sure that the bearings, rings, etc. on my car are not as good as they would be if I had never had the intermix. But I have good oil pressure and compression and spent my time and about $1,500 and now have almost 23,000 on the car since the fix, it runs strong ad I am happy. If it had required a new engine the car would be in a junk yard now. I could not have afforded a new engine and would have questioned spending what the car was worth on an engine. I have now worked with many others on fixing their cars with intermix problems and it is being done on a regular basis. If you want more I formation, etc., let me know, I would be glad to help if I can.

This was my summer last year, oil/coolant mix, stress, decisions. My shop, MRAZ outside of Milwaukee found a split membrane in the AOS. Also found the dreaded D-chunk. So, after doing a lot of thinking about next steps, I finally decided to rebuild the engine. The choices were as previously listed numerous times by others. The engine had just crossed 80k on the odo so I was already researching and planning a rebuild. I had made myself familiar with L&N, Raby and all of the discussions. The car was solid, and I owned it. MY 2000 996. I decided to go ahead with the rebuild. For a similar investment to replacing the car, you can now have some fun with the engine. L&N bored the case, now my 3.4 was a 3.6 with new L&N cylinder sleeves and pistons. With the case and guts apart, all new can go in as appropriate. Work with your engine builder on the appropriate replacement parts list and mix for desired results. Get a port and polish while disassembled. If you have an experienced engine builder that you can visit and share the journey with, well, that's an added bonus part of the experience. When it is all done, you have that journey and added understanding of your baby as well. In the end, no stock Porsche engine, as good as they are, will run like a well thought out rebuild. I bit the bullet, endured some pained looks from my better half, but now, wow! Glad I did. Option was another used Porsche ultimately heading towards a similar fate. Instead, I now have a whole new beast. Good luck! And look on the bright side, the fun is just beginning.

The car is a 2000. If it were here it would join the 7 other 2000& 2001 intermix cars we currently have in work. All of these had cracked heads. We see this happen all the time with these year models. Of the 7 we have here now we have repaired 6 of them as collateral damage was minimal and the engine was healthy otherwise. One of them was driven to death. You are what we consider "local", so give us a ring. This is a best case scenario failure in terms of expense. With cars here from 23 states, receiving one from a neighboring state is a breath of fresh air and very simple.

Intermix Guardian? Was this a manufacturing defect, such as a bad mold?

The 00/01 heads have small capillaries that collect debris. This leads to localized hot spots and resultant cracks between the coolant and oil passages within the heads. We know what aggregates the issues. Since 2011 these failures have made for more failure jobs than failed IMS bearings here. It's so predictable that we can pinpoint where the crack will be even prior to tear down in most cases.

Is there any preventative measure that can be done?

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Tom, can you please describe how they found the split membrane in the AOS? Was it a standard AOS failure or a defective part that allowed oil into the coolant. I am curious if this is a more common source of intermix than we all realized. Thanks, TomF

A manometer test can be used to check the integrity of the AOS. Of all the cars we have seen with intermix only one was an AOS and only one more was the heat exchanger. All the rest have been cracked heads and slipped sleeves/ cracked cylinders. If a car is a 2000 or 2001 I don't even check the AOS or heat exchanger anymore, we just pull the heads. In every instance this far that's been the proper course of action. The 2000/01 ailment is cracked heads.

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After disassembly, we looked at the membrane, it was split. When we saw that, I did some more specific searching on this forum and Pelican's. Saw many references to AOS failure. It was noted in those threads and other places that the AOS replacement should be a maintenance item. Not being an engine guy like Raby and others, I just looked at that membrane and said to myself "that is a failure waiting to happen." I am told that the coolant circuit in the AOS is to help minimize moisture freezing in the winter, but to me, it just makes for a very complicated system that ultimately becomes a weak point. My opinion, and I am by no stretch an engine genius. If the winter issue is the reason for the coolant circuit, then, IMO, it is another example of engineers chasing a problem versus stepping back and taking a fresh look. (no disrespect meant to any and all engineers on the forum, you make the world work..... and Porsche's .) So, I believe a standard AOS failure (it was 12 years old after all!) I can't offer a repair schedule for AOS, but being this is a 996 forum, if it hasn't been replaced, it is probably time to do so. The membrane is a fabric that moves and is subject to repeated heating cycles, not to mention the chemicals in the fluids. It will not last forever. It is fairly accessible. Just my observation and opinions.

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Water pump impeller blade particles?

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And rubberized coating thats used on OEM head gaskets. At the areas where the head gaskets hang over the passages between the heads and crankcase enough material can shed to allow for partially obstructed coolant capillaries. We have actually removed this material from deep within the heads during milling operations associated with crack repairs. Its easy to tell exactly what it is and exactly where it comes from. You won't read this anywhere else, because no one else has discovered it; because most don't pay attention; and are not exposed to enough of these situations to put the pieces of the puzzle together. I have never stated it online before. This is a circumstance that cannot be avoided through preventive procedures, parts swaps or procedures.