New to me 996 with coolant intermix issue...
 

Hello there, I just acquired a 99 996 Cabriolet with a oil in the coolant and oil intermix issue. PO had replaced the oil cooler hoping that it would cure the issue but sadly it did not. Suspect a cracked head and wondered what other things should be looked at with the engine out. It has had the IMS bearing replaced and a new clutch installed. The car has about 60,000 miles on it.

The first thing to do is to flush out the coolant lines. The oil will eat them from within and you will have a costly problem.

Flush out using just water or something stronger?

Based on my experience the issue of coolant hoses is overblown. If you check my posts I had extensive intermix in 2008. Not sure how long it was until I found it. Replaced the oil and coolant in Sept/Oct and the intermix came back. Parked it until April of 2009, then dropped the engine to fix a cracked head. I did flush the cooling system, mostly by running and changing distilled water through the system several times. I did have theradiators flushed and drew some rags through the ridged tubes when the engine was out. There were still traces of oil for sometime in the coolant but I changed it yearly and within a couple of years it was gone. It has now been about 10 years and 50,000 miles.i think I have replaced one or two hoses in that time, the others have worked fine but are definitely showing their almost 20 years of age.

So I have always been curious about the damage to the hoses and who has had an intermix and experienced such problems? By the way, there are a lot of hoses in these cars and it will cost hundreds of dollars to buy new ones.

Also, the first thing I would check is for a crack on the #1 cylinder, inner exhaust valve spring seat, you might be able to see it by removing the spark plug tube. If not remove the cam covers, cams, lifters and lifter block and take a look. If you want some help/advice, pictures, etc. let me know.

i also have a new, never installed 1-3 cylinder head that I need to sell one of these days.

Read this
https://rennlist.com/forums/996-foru...tra-nasty.html
a clever guy discovered a mix of Shout laundry stain remover and very hot water works well to break up the nasty mix. I tried it also and it works, (for the hoses and tubes) along with a combination of the mechanical methods described by Doug.
I took the radiators to a rad repair shop in downtown Asheville, they flushed and pressure tested them for me.
I don’t know of anything that cleans out the oil cooler, due to its unique design and the fact that both oil and coolant enter it. Just replace it.
BTW, cleaning up this intermix is the worst part of the project by far. Everything else is easy by comparison.

Oil in the coolant typically indicates a cracked head, Coolant in the oil typically indicates a bad AOS. if you are comfortable starting the car, check the AOS function using a manometer and a modified oil filler cap. I can lend you them if you wish.

Thanks Doug, that is encouraging. Once torn apart and investigated will compare welding the head vs a new one ( yours ;-)

Hi, Thanks for the offer. The car does run and I believe that the AOS has been replaced... However I may take you on testing the AOS just to be sure.I'm in Hendersonville and a member of the Asheville Porsche Club.

Carl v S

Hi Carl! Glad to see you here with your new-to-you 996. Does Janice know you're ignoring the honey-do-list?!

Well Howdy! Nice looking Cab you’ve got there!

Welcome to the madness! Did you buy the yellow one?

not to add more variables to the mix, but isn't intermix also a sign of engine porosity which can only be solved with a new case/block. I thought early m96 engines where prone to this.

Yes indeed. Beautiful car, nice options and only 62,000 miles.

https://cimg3.ibsrv.net/gimg/rennlis...c3ea61788.jpeg

I guess I’ll find out once the engine is out and can do a thorough inspection of the heads.

Speed yellow is my favorite color....