Brown oily substance in radiator overflow

[gooch]

I am looking at purchasing a complete ac cobra
Upon doing an inspection i noticed the radiator overflow is almost empty and there is a brownish oily substance in it. It also seems to have a lot of sediment in it.
I checked the oil and it seems ok.
There is also a small leak it seems at the bottom of rad. Fluid looks exactly the same as in overflow
Thoughts

[NAZ]

Sounds like what you get when an oil to water heat exchanger leaks into the coolant system. Many Fords come with these heat exchangers (oil coolers) and leaks are problematic. You can get a similar looking mess when someone uses the wrong coolant to top off the system. If your engine is not equipped with an oil to water heat exchanger then my guess is the second scenario. However, if your engine is equipped with one or more of these type heat exchangers you need to determine if what you're seeing in the coolant is oil and if so, fix the oil leak. In either case the coolant system must be chemically flushed (triple flushed) and the overflow bottle replaced as you'll never get it clean. If you're buying a car in this condition I'd make the sale contingent on the owner fixing the problem to your satisfaction first.

[AC Bill]

I was thinking a head gasket is gone. Oil getting in to the coolant.

[NAZ]

Bill, sure a good possibility. And a much bigger problem to correct.

[Avalanche325]

I agree that it sounds like oil in the coolant.

Likely a head gasket. Not that big of a deal in itself. An afternoons work to replace it. "Why did it blow?" would be the bigger question. Could be just one of those things, or something major.
It could be the intake manifold gasket or it just isn't torqued properly. More likely water in the oil than oil in the water on this one.
Then comes the ugly stuff. Warped or cracked head. Cracked block.

I would certainly treat this as a potential major issue. If you don't walk away, due diligence needs to be taken. You either need to figure out what it is prior to purchase, or get a good enough deal to where replacing the engine wouldn't be that bad.

[HCP 65 COUPE]

Like avalanche said plan on tearing down the whole engine for inspection, new rings and bearings and maybe more,maybe alot more. Coolant in the oil will destroy an engines internals very fast, brearings rings valve guides all lose lubrication and sustain corrosion damage the longer the engine runs in this scenario. The likley cause was an overheat and head gasket failure or an intake gasket that never sealed from first install.

[BEAR-AvHistory]

Did you check the oil filler cap for a milky substance?

[AC Bill]

Seller may have recently changed the oil, and not run it since, so clean oil isn't a reliable tell. Be great if you could look into the rad, but you might get additional hints if you pull the cap on the T-filler, and take a gander for any signs of oil contamination.

[Norm B]

I suggest, if allowed by the current owner, you remove the coolant filler cap and start the engine. Do this when the engine is fully cold. It might blow a little coolant out when the engine first starts because the water pump spinning displaces some fluid. I normally put the palm of my hand over the filler opening to seal it and let it push this initial surge into the overflow tank. When I don't feel any pressure against my palm I carefully remove my hand a watch for bubbles. If the feeling of pressure never goes away then have the engine shut down and wait for it too. Bubbles or building pressure on a cold engine normally indicate the failures mentioned by Avalanche325 in post 5.

HTH

Norm

PS. MAKE SURE THE ENGINE IS FULLY COLD AND DON"T RUN IT TOO LONG. YOUR HAND WILL GET HOT!

[Mesa Mike]

I agree with AC Bill. Head gasket is bad.

[Sgt.Gator]

I race Subarus which are infamous for head gasket failures. I've found the UVIEW 560000 Combustion Leak Tester to be invaluable. It can tell you BEFORE you have any sign of oil in your coolant that there is a leak. It reacts to CO2 in the coolant, and it only takes a tiny amount to get a reaction. I use it on every car I'm considering buying as part of a pre-purchase inspection and also every 3 months or so I check all my cars as routine maintenance.

[Avalanche325]

I race Subarus which are infamous for head gasket failures. I've found the UVIEW 560000 Combustion Leak Tester to be invaluable. It can tell you BEFORE you have any sign of oil in your coolant that there is a leak. It reacts to CO2 in the coolant, and it only takes a tiny amount to get a reaction. I use it on every car I'm considering buying as part of a pre-purchase inspection and also every 3 months or so I check all my cars as routine maintenance.

I didn't realize how inexpensive those were these days. I would spend that $50 if you are still looking at that car.

I agree with AC Bill. Head gasket is bad.

Likely, but I wouldn't bet the farm on it. A cracked block can have the very same symptoms. I bought a 66 Mustang fastback with the same symptoms. I hoped for a head gasket. But it was new engine time.

[gooch]

So I had a performance shop inspect the car and there is a small leak in rad. 1 drop every 2 days basically. The shop recommended one of the rad sealer pills. Everything else is perfect. No oil like I thought. Compression was good.
Car only has 1000k on motor.
Needless to say I bought it right away and I have had a stupid grin on my face since

Thanks for the advice

[AC Bill]

Congrats on your new roadster. I hope you enjoy many miles of fun and safe cruising.

I'm going to guess that the brownish substance and sediment, you mention in your first post, is actually some Bars Leaks the previous owner may have been adding to stop the rad leak. That will discolor the normally green, or sometimes red colored antifreeze.