mtnman82

I drained the cooling system today and noticed a blue/gray coating on the inside of the coolant reservoir (reservoir was replaced by a previous owner a couple years ago and is still white, not yellow). The car had blue anti-freeze in it. I stuck my finger into the tank to check it out and it's a fairly thick slime-like substance. Is this normal (I assume not)? Will flushing the system remove this? Should I be worried? I'm assuming it's like this through the whole system, which can't be good ..... It's never run hot, even in the heat of the desert with A/C on it never gets up to half scale (usually just above the 1st thin line).

Edit: I poured the coolant into a white bucket to check it out and it is green, not blue.

Tye

This happened on my S2 when the oil cooler seal went bad. Might be head gasket problem?

mtnman82

Not what I wanted to hear. Anyone else???

hosrom_951

Well, it is either oil (oil cooler seals/head gasket) or the coolant is so old and the system hasen't been flushed in a while. It is recommended to fully drain/flush/replace coolant after 2 years.

Best thing to do is to take off the coolant reservoir, clean it out with petrol/diesel and fully flush the system......

But i would find out if it is oil or just some slimey muck in the system first.

JustinL

I'll second the oil cooler seals. When oil and coolant mix they make that snot stuff and over time will continue to clog your cooling system. Change the seals and giver a couple of good flushes with water and a liquid dishwasher soap and she'll be squeeky clean for another 15 years.

Justin

Zero10

There is always a chance that it could just be residue left-over in the system.
You mentioned you had the vw/audi blue coolant in there. Perhaps there was an incompatible coolant added to the system at some time, or left in when it was converted to vw/audi blue.
IMO, flush the cooling system, and see if it returns. To properly flush the system, actually get a can/bottle of cooling system flush, and remove the resevoir to clean it as well. If it returns, my money is on oil cooler seals.

ibkevin

If it's motor oil, what they said. If it's slimecheck this.

Another great tip from KuHL 951, Steve, is "The gravel does work great, even better if you go to the pharmacy and buy a bottle of Oxalic Acid crystals. It's specialty is removing ferrous and mangenese staining which is the cause of most of the color in the tank. The heater tube is still steel resulting in the red color."

ibkevin

sorry, the link didn't capture the entire thread. Look for that title on page two of this forum.

mtnman82

Hmmmm, I'm in the process of doing the front end seals/water pump/oil cooler seals presently. I logged off last night with a lump in my stomach thinking 'crap, now I should pull the head too, so even more downtime - but might as well now that I'm in there ...'. The actual work of doing all this han't been hard, it's just taking me forever because I don't have a lot of time to work on it. The slime doesn't appear to have any oil in it, but it is a grayish-black so it's hard to tell. it's like a watered down vaseline consistancy. I'm thinking I might skip pulling the head for now, in hopes that it is the oil cooler seals. I have an oil leak in that area that I couldn't pinpoint too. I'm gonna finish the re-seal job, flush the cooling system good (and probably clean the coolant tank - thanks for the link kevin), and then see if it returns. If it does return, then it's time to pull the head.

Any recommendations on the coolant? I'm not in for doing the watter wetter thing (just yet, anyway), just wondering if good old all make/all model/mix with anything Prestone is sufficient, or if I should look for something else - maybe something lighter in color so I can tell easily if there's any oil getting in it? It might be in there a while if everything is good, but if it's not all good it'll be dumped. Thanks everyone!!!

ibkevin

That is kind of a toss up. Skip the head now to minimize the pile of parts sitting around or retension the cam belt twice.

I'm looking forward to doing a good flush on my system when I pull the alternator to install the adj volt reg and Iceshark cable upgrade, hence the spare tank cleaning.

Coolant selection has been discoussed at legnth, check the archives.