60to0in0seconds

Hi, I was wondering if anyone has had this problem. I have a 1991 20v 3b engine and I was running the Blue Pentosin coolant. I recently had a hose break so i mixed in some green coolant (unfortunately all i had in a pinch.) I have run it that way for that last couple of weeks without problem. Now I have noticed a brownish/reddish film floating on top of the coolant in the bottle. Because its floating I thought it might be oil getting in there. Also, the oil in the engine looks good. I guess my two questions are:

1. can mixing the generic green antifreeze with the Pentosin Blue coolant cause this?

2. How can I tell if my head gasket is cracked and possibly leaking oil into my coolant because a compression test wouldn't detect this right? Also, where else could the problem be coming from? Is it possible the turbo is mixing oil and coolant?

Any ideas would be greatly appreciated!
thanks!!

aerohr

When was the last time you did a coolant flush? Its likely just some rust that has accumulated from your radiator(s).

Ideally you want to have the blue antifreeze in there because it has a protectant that is supposed to keep the rust from forming... but likely in the past your car hasn't always had that and, well, I don't know about the 100% ability to keep rust out with the blue.

Before you start freaking out, I suggest a simple operation... flush your coolant with one of those coolant flushing products from autozone or something. If you haven't done it before this is how it goes:

Remove the hose the connects to the block on the driverside (front of the engine... its actually for the thermostat). This will drain the majority of your crappy coolant out... but not all. Don't forget, you have a secondary radiator behind the front bumper that likely plays a role in the rust level and may never have been flushed. To access this, I suggest popping the bumper off and removing the few bolts that hold the radiator in place (kind of a pain in the *** but not at all a big deal) as well as removing the two hoses from it to drain it out nicely. While its out you may as well run some water through it with a garden hose to clean out what you can. Once all the coolant is drained from motor and aux radiator, put all the pieces back together and reconnect the hoses.

Fill 'er up with some water and that coolant flush product and drive around for a few hundred miles to get everything loosened up. Re-drain the coolant with the above procedure - and maybe run some water through for 5 minutes or something with a hose to make sure all the rust and crud is out.

Reconnect all the hoses and fill it up again with coolant in the appropriate fashion... that is, once the fluid level is high, turn the heater fan on high/hottest possible setting to get it all circulating to allow the max amount of coolant in while you continue to add coolant to the resevoir. If you are really **** you can pull off the top hose to the reservoir (little guy) and pour in some more coolant in there to get it super topped off.

You now have a super well douched coolant tract.


and for question number 2...
Your head gasket is probably fine - if you see frothy/milky **** on your dipstick or in the oil start to worry a bit more. Your turbo is likely fine, too - if it was mixing oil/coolant it probably wouldn't be feeling to well and I haven't heard of that happening before. Douche your coolant system out really nicely and my guess is that everything is taken care of.

boxerfan

NEVER MIX COOLANTS! Flush immediately.

audiqv8

This way you can mix an equal amount of correct antifreeze when you get a chance. Most grocery stores carry distilled water. Or you buy that real expensive bottle drinking water in a real pinch. Never mix antifreeze of different type.<ul><li><a href="https://forums.audiworld.com/v8/msgs/75920.phtml">Previous Post</a></li></ul>

60to0in0seconds

90 Quattro a couple months ago, but I figured you guys would probably be more familiar with the 3b than the 80/90 forum (although i asked them too!). The problem started about a week after i mixed the blue and green coolants.

I just got some prestone flush and I am going to clean that baby out! Hopefully that will be it.

Thanks again!!

aerohr

I used the prestone flush myself with good results. Good luck, keep us updated.