Need Advice: Potential Intermix

I have a friend who has a 1999 996 who brought it to me to do some work. He obtained the car about 4 months ago and has driven it about 4,000 miles, it has about 66,000 miles total on it. Notable maintenance is that he changed the oil about 3,000 miles ago with Liquid Moly with the MolyGen which has UV dye in it. On the list of things to do was the water pump and a low temperature thermostat. When I looked at the reservoir when he dropped it off, I did not see pink coolant in the reservoir, but it looked like purple coolant. I purchase G12 to put back in the car. Here is the tank before I released the pressure today, the car was slightly warm as I just did a tiptronic transmission service and it was running on the lift. It seems slightly high in the reservoir. On my car, I run it lower and it's very happy. I drained the coolant first from the drain plug and it was basically clear, but once it hit the bucket, it was black. I took a few samples. Here are pictures of the coolant after it came out, it's hard to tell, but it's purple coolant. Another note: The coolant had a heavy AMMONIA smell when I drained the coolant. Here is what it looks like in the bucket, the oil is definitely on the top and in the coolant: So Ray came over after I called him and I learned that he used the Liquid Moly with the dye in it, you can see it in the coolant hose that goes to the thermostat housing, I thought it was UV dye, but after looking at it in the dark again, I do not see UV in the coolant. So it definitely appears that is an active leak unless the coolant just has left over oil from a failed AOS, but considering the black oil (I'm assuming it's oil), it has a leak. He has extensive records on the car, and it's been highly maintained. The AOS was replaced at 53,000 in April 2021. It has about 10K miles on it. Done by an independent in the Miami area. Here is the reservoir, in the first picture you can see where I wiped the oil or muck or whatever it is. So the next question: What do I do next? I haven't taken the water pump and thermostat off yet, so I can easily put the car back together. I was thinking filling it with distilled water (we are in FL) and doing a crankcase pressure test and I was also initially thinking of flushing it a few times with water, but I don't know about the flush just yet. Potential issues: AOS bad Oil Cooler Leak Cracked Head Just trying to go slow and ask everyone here what to do next. Appreciate your input! BTW, my car is a 99, ocean blue metallic, areo package, sport II wheels. Guess what? So is Ray's! I met him a week ago at Daytona International Speedway at the vintage car races when I saw his car.

Hi Paul, It doesn't look like oil to me... I have only seen oil in coolant in two ways...1 .Oil on top of coolant with a very clear and distinct separation between the oil ( top) and the coolant ( bottom ) ,because oil is lighter ( less dense) than coolant...or..2... oil and coolant completely mixed which produces a thickish mud/milkshake light brown/tan coloured liquid... I have seen it mentioned time and time again on the internet that all 996.s had and are suppose to have pink coolant...This is not correct. The original Porsche Coolant used up untill about 04-05 was green....The pink replaced the green and they were compatible..( At one point we had both the green and the pink on the shelf untill all the green was gone) So if that car still had the original green and someone mixxed in a purple with a dye, that may be why it looks black....Green and Purple probably make an ugly nasty looking ..... I think I would just flush it out with water and get all that whatever out... then a proper mix of the nice looking Pink stuff....

Probably somebody mixed the wrong liquids in that reservoir. Check this as a potential suspect: https://www.reddit.com/r/Jaguar/comments/14jjxng/2019_epace_d150_coolant_smells_like_amonia

Hard to tell from the pictures. Is the black stuff on top oily? If so it could be intermix. Looks a bit dark for engine oil tho? Ammonia snell could be transmission fluid. I think these tips have a heat exchanger for the gearbox that sometimes fails and causes intermix. But without proper analysis thats still speculation. If possible id pressure test the cooling system. That should give any cracks/leaks away and is a cheap thing to do. (system doesn't need to be filled with coolant to do so, just makes it a bit harder to catch any leaks outside the engine).

Thanks, the first thing I was going to do was to check if there was combustion materials in the coolant. I don't know if I can do it with the coolant I already pulled out of the car, but I'm going to get a kit and try it on the "test" sample, I can also send the sample out for analysis. If it doesn't show, I think it would be prudent to fill with distilled water and test again with a hot engine drawn out of the expansion tank. Ray, the owner, stated that the vent on the tank was in the up position when he bought the car, he drove it for a while like that until he noticed it. It has an aftermarket expansion tank cap (we'll replace it) and when I went to take it off yesterday after running the car at idle for transmission fill, there was NO WAY I could loosen it by hand. The car had been off about 30 minutes at that point. I thought that was odd and I had to use a large set of slip pliers to crack the cap loose. I don't know if that's because the system had excessive pressure or somebody used a pair of pliers to tighten it. Will report back.

While i respect PT3 educated opinion,,, sure looks like oil in there to me. But pics on internet can be very deceptive. If you have "combustion materials in the coolant" more than likely you'd have steam coming out your tail pipes... If it were mine... I'd pull drain plug, pull apart all the hoses at the pump/t-stat/etc I could get to easily. Let what will drain out drain out. Blow some very low pressure air thru whenever you can get to, too help blow out any old coolant. Or use the total drain method from this forum. Then I'd Get out my garden hose with a little ball valve shut off attached on its end to be able to control the water flow easily, wrap its end with a rag to help seal it to hoses/connections somewhat, and direct a hard full pressure flow thru all hoses/nipples you can get to. Let it blast thru & drain out hopefully all/most of the contamination... Also run the garden hose thru the coolant tank with bottom hoses off. I would not worry about hard tap water causing calcification in a 26 year old cooling system/radiators at this point in cars troubleshooting life. Water pump/t-stat/radiators probably could all use a change out anyhow.... With the looks of that coolant, you've got a lot more important internal cooling system problems than worrying about hard water contamination. Does your tap water suds up easy with soap..? I'd vacuum refill with garden hose water, bleed off all air best as possible.Maybe add in your fill charge a $12 gallon of the Prestone universal concentrate all vehicle antifreeze for stopping any corrosion/calcification/freezing. Leave tank bleeder bail in the up position. Let it fully warm up, take a ride around the block, let it fully cool off and top off coolant tank. Drive it for a while. Keep an eye on coolant level and how the coolant looks. This is a inexpensive temporary fill to see if coolant stays clean, has no over heating, has no intermix or contamination. Then go from there. If all is good, do another drain/water pump/t-stat/radiators/pink coolant fill and call it a day. If its not,,, you'll have to think your next step thru... jmo

Allcool, thanks for the advice, it is good. Here is what went down this morning, things are looking bright. When I arrived this morning, my car was smelling the other car's ***: It was interesting seeing the sample coolant that sat overnight: The owner of the car called the previous owner and the PO verified that he added non G12 coolant in the system some time ago, he thought maybe it was somebody at Autozone who did it, so at least we know it was a different coolant mixing. ChatGPT does state that if you have two different coolants they can attack each other and create Amines which produces the ammonia smell. I'm not saying 100% that was the issue, but maybe it was. I filled the system with distilled water (have the vacuum fill tool) and as it was warming up, it was foaming up in the expansion tank: Once it was warmed up, I did a test to see if the exhaust was in the cooling system, it was negative: During the first distilled water drain, the drained coolant looked clear coming out, but it would foam up like foam at the ocean (sea foam) and the coolant was dark, but not so bad: At the bottom of the bucket was more of the green stuff that you could see in the coolant pipe above, but after each fill and drain it went down in volume drastically: Ray came over bringing more distilled water, we put a bottle of this in at the same time, this is the second fill with distilled water: During the drain after we ran the car about 5 miles, there was NO MORE FOAM coming out of the coolant! The ammonia smell was 95% gone, but still a tiny hint to it. The first drain still had a high smell of ammonia. So we filled it one more time with distilled water and ran it another five miles, leaving the car for now and tomorrow will drain it, if it looks pretty clear (the expansion tank fluid looks perfectly clear with no foam), then I will change the water pump, thermostat housing and put in Pentofrost SF G12 mixed with distilled water. Please make a sacrifice to the Porsche coolant gods tonight for us!

That foam is really weird, never seen it, but it might be a chemical reaction of sorts going on. Hope all is good now! Btw, why did you check for exhaust gasses? From what I read; If these engines get intermix, typically a crack develops between the cooling & oil passages, hardly ever to the cylinder. Therefore a coolant pressure test might be more conclusive.

Checking for exhaust gases is easy, and after thinking about it last night, if it wasn't intermix, it could of been exhaust gases. Hopefully all is well.

To close the loop on this query, I drained the water this morning and what came out of the engine drain was about 99% clean and no particulate. The radiator water was similar with a tiny amount of particulate. Changed the water pump and thermostat, new belt, and reassembled. If you don't have a Gearwrench serpentine belt tool kit, and you don't have a serpentine belt tool, get it, you'll thank me later. I use it for so many things, not just serpentine belts. The green stuff is still in the system, but you can't easily wipe it off. I am thinking a new oxide layer is going to be created over the next few months with the correct coolant. There is that one difficult bolt to get in at 3 o'clock. Once I got it started from the top, I used a flexible 1/4" drive to drive it in, then switched to a quarter inch rachet to tighten. New G12 went in, took a lot of coolant, I did two test drives of about 15 miles and 10 miles, after the 15 mile drive, the low coolant warning light came on, and I added about another 1.5 liters, then after the next drive, I still had to add about 750 ml. So at least I know it burped. I used a vacuum fill system to fill it. Old thermostat: We are good to go! Or at least that's what I think. Was very satisfying to help out. I started my own little auto repair business in Port Orange, FL a few months back, if anybody needs anything who is in the area, let me know. I'm pretty cheap also.

Yesh, I didn't think it was oil / intermix, it just didn't fit the MO ( Modus Operandi)... Glad to help... So you will be doing some of the Porsche Gods work ??

great job! thx for sharing/documenting really helpful