Oil in Coolant - 99 GTP

[Brent S]

I've come to the conclusion that I'm probably getting some oil in my Dexcool coolant. Car has 105K mi. It doesn't seem to be too much - maybe about 5 or 6 drops worth every month; which seems to be rising to the top of the filler neck. I've read a bunch of other posts, and it really seams like it's oil and not coolant "sludge" or tranny fluid. Coolant was replaced at 50k mi and again at 100k mi. Oil changes do not show any coolant in oil. Also, I think this may have something to do with the Low Coolant light issue I've been having. I wonder if a film of oil can coat the sensor's electrode, screwing it up. Maybe? The sensor was replaced at about 95K mi., as was the thermostat. I've been taking some paper napkins and blotting them into the filler neck, which seems to soak up the oil (as well as the coolant), and then I refill the coolant. Any suggestions?

[richtazz]

You can have a sample of your coolant analyzed to see if it is oil. If it is, then you need to find out how it's getting in there. If it is just sludge, a good cooling system flush may take care of it. If it's trans fluid, you probably need a new radiator.

[Brent S]

Ok, I just called Napa, Auto Zone, and Auto Barn; none analyze coolant. Where/who analyzes coolant?
I would be very surprised if it's not oil, because it's deep brown, feels like oil, stays rather separated from the fluid, etc.
With this small amount (a few drops every couple weeks), you think I could keep going and simply monitor it, before I jump into bringing it somewhere for a pricey bill? I mean; does a small amount of oil really damage anything (other than my Low Coolant sensor)?

[richtazz]

Oil in the coolant could damage other sensors in the cooling system (like the coolant temp sensor for example) as well. IT can also build up and coat the surfaces of the cooling system, causing blockages and less efficient heat transfer. If oil is getting in the coolant, it could also be getting in the combustion chamber, which can damage oxygen sensors and catalytic converters.

[BNaylor]

Best way to test for any tranny fluid or oil contamination is drain some from the radiator drain plug over at the driver's side of radiator engine side. The stuff (sludge) is probably heavier than coolant. Hard to get to the drain plug but it can be done. Drain into a container.

IMO what you are seeing is sludge. I get the stuff on the bottom of my radiator cap and lining the filler neck periodically in my GTP. And in the coolant reservoir tank too. But here is the catch all the old Dexcool was thoroughly flushed out a couple of years ago and I switched to Prestone 5/150 green extended life coolant. But from what I understand it is OAT (Organic Acid Technology) based just like Dexcool. The sludge is an effect of air, the heat and the coolant reacts by turning to sludge. Good idea to top off coolant directly in the filler neck instead of into the coolant reservoir only but also keep coolant level well above the half in the reservoir tank.

BTW - I think raw tranny fluid and motor oil will float to the top so that may not be a valid test but in sludge form may be different.