My Ford Taurus which runs fine just had it's coolant recovery tank turn dark. I pulled some of the coolant out and it's clear but there's dark, oily particles floating around and it looks like they stuck to the sides of the tank giving it a dark appearance from the outside. Was fine one day and not the next. Engine oil is not contaminated so the next thought was an internal leak in the radiator(new) allowing transmission fluid to leak into the coolant but the transmission fluid level doesn't seem to be dropping. Next thought was deteriorating hoses or heater. Since Volvos have problems in this area I was wondering if anyone that's had a heater core start leaking experienced a dark tank first? Dissolving plastic floating around?

 

Inclined to think head gasket is imminent.

 

UPDATE: I took a closer look and there's nothing floating around except a little oil on top of the surface. The tank itself is dark because it was stained by something. I hope it isn't the head gasket. Are there any DIY things I can do to check it?

 

Engine oil can enter the cooling system through a bad head gasket or a cracked head or block.

Transmission fluid gets in the cooling system through the radiator cooler.

 

just about all cars, at least all european cars I've had, the tanks turn yellow then brown with age and heat. at some point the plastic becomes brittle, then they crack and start leaking.

any sign of oil slick, like iridescence on the surface of the coolant in the tank, is bad. as lev says, can be sign of impending head gasket failure, or radiator cooler failure. also look for white cream on the inside of the oil cap, and on the transmission dipstick, these means coolant is getting into the oil or ATF, also both bad news.

 

Think about it... the coolant should be nothing but clean green.


If you have owned the car for a while, and coolant goes oily, you have a problem.

 

Yes, it's obvious something leaked in. But strangely, it seems ok now. I skimmed the oil off the top of coolant and checked the coolant color and level, the oil color and level and the trans fluid color and level, and all seem fine and the car runs fine. Is it possible for a head gasket to start to leak and magically reseal itself and stop?

 

its possible for a leak to be intermittent initially, where maybe it only leaks a little when very hot and under high acceleration, or something, but eventually it will get worse until it blows completely and you'll need a tow.

 

Today I did a hydrocarbon test on the expansion tank for combustion gases and there were none. So either, it's what you say about high acceleration or it's an internal radiator leak, which I know is possible in theory but I've never heard of that happening to anyone. And if it did wouldn't there be some coolant in the transmission? The dipstick looks clean and red, as it should. And my radiator is less than 6 months old. Strange.

 

maybe it was just some left over oil that got into the coolant during servcing, like when you swapped hte radiator.

 

Possible but the expansion tank(1 yr old) was clear one day and stained dark the next. Something happened 3 days ago.

 

all I would do at this point is pull the tank, clean it very well, flush coolant and see if it happens again.

sounds like you have a blown headgasket. Hard to diag over the web...

Tranny fluid is red. You would notice it in the coolant.


It couldnt hurt to drain the tranny fluid and see what color it is. its not hard on these cars.

I would also plan for a headgasket job. Get ready to do some 8 out of 10 skill level wrenching!

 

All valid possibilities, but here's a thought. Initially a little oil got in the coolant. But there is no coolant in the oil or the tranny. And as I said, I did a co2 test on the tank and there is no exhaust fumes in the coolant. Everything works fine. A head gasket cannot reseal itself. So I think I might have slightly warped the head. And at low and medium rpms it still seals. But like Pierce said, maybe at high rpm when the pressures are greatest it loses it's seal and the leak occurred. Possible?

 

who knows?!

you could do a pressure test on the cooling system...

 

If you do need to do a head gasket and you don't value the car much, or you just are unwilling or unable to do the job, you can consider a product called Blue Devil. it's an additive you just put in the cooling system and it works! It really does! It seals breaks or cracks permanently and without side effects. I used it on a Saab that was visibly losing coolant and oil, and it sealed it all up! The engine has to be cold when the stuff is added and run for about an hour, and done!

 

I will.

 

It's just a work car and I don't think I'd sink money into a rebuild but if things get worse I was thinking about using a product like this. There's many out there and it's good to hear that someone has positive personal experience. Thanks, I'll check it out.

 

How good are your water hoses. If they are old they will deteriorate inside and shed black rubber that will stain the tank. Check for bulges and soft hoses and if you have sufficient mileage on them you might consider changing them.

 

Just crack a raw egg and dump it into the coolant.

 

Because?