99Stangsix

99 Mustang six, auto, 180,000 miles, running great - original engine and trans - took it to the dealership for an oil change and they found quite a bit of oil in the bottom of the coolant reserve bottle, and radiator. They cleaned it out, added a dye, and said to return in about 500 miles to check it out again. Did this, and they found no oil in fresh coolant, but radiator hoses were swollen due to oil they said -
About 3 years ago my electric cooling fan died, and I blew the upper rad hose - I bought an expensive hose bandage, loosened the rad cap, and tried to limp home about 13 miles away, keeping a close eye on the heat gauge. Didn't realize the fan was out, and the hose blew again right next to the hose bandage. I pulled over when gauge started to show hot, added water if necessary - was told this was a mistake, temp gauge does not register accurately if coolant level is low -
Car been running fine all this time - thoughts on oil in coolant? Dealership said unlikely head gasket would blow and reseal at all - am wondering if maybe someone actually dumped some in perhaps when I had the hood open briefly at an auto parts store or such -

08'MustangDude

Head gasket...

Urambo Tauro

Yeah, could be head gasket, or possibly an internal radiator leak (transmission oil). Strange that they couldn't find oil 500 miles after cleaning the old oil out. How was the dye supposed to work? Did they add it to the oil, then look for that dye to show up in the coolant?

Head gaskets usually reveal themselves through a loss of coolant first. Was the coolant low? And was there ever any coolant in the engine (or transmission) oil? You did mention having to add water, but only in the part about limping it home after a blown rad hose 3 years ago. (Speaking of which, I didn't know they made bandages for radiator hose. Would have been better off just buying the right hose instead...)

I doubt somebody just randomly dropped some oil in it while you weren't looking, but stranger things have happened I guess.

Derf00

Compression test the motor, pull the plugs to check their condition. Pressure test the cooling system. If those don't reveal anything you could go as far as a leak-down test to confirm things. I have seen leak down tests find things that a compression test could not.

sremle

Hmm, I may be having a brain short circuit, but I think the oil would be on the top of the antifreeze?

99Stangsix

I notice when I use a handheld pump to remove the coolant from the reserve bottle, there is sometimes oil dripping off the tube of the pump, so I assumed it was at the bottom of the reservoir. Very occasionally I would see dark circles on the surface of the coolant reserve bottle. Last time I removed the coolant from the bottle it looked normal, bright green. Currently the car has almost 197,000 miles on it, runs great, uses little oil, going in to talk to ARCE motors on next Saturday to schedule getting car in to be checked out -

sremle

I know for sure oil does float on Ethylene Glycol. I do not use anything but Ethylene Glycol in any of my older engines, gas or diesel. Oil may mix with the newer antifreeze blends containing Propylene Glycol. Like salad dressing mixture of oil and vinegar, the oil is generally on top.

If you say it was bright green, I suspect you are using Ethylene Glycol. The dark rings may be dirt from the inside the block, or aluminum from aluminum components in your system breaking down. The black from the aluminum would be similar to the black you get when polishing aluminum wheels with Mothers Aluminum Polish.

Also do you use the same hand held pump for oil transfer?