Milky Oil

[Sonnysib]

Good morning everyone. I have searched and couldn't find answer so I'm posting new thread. I am not a serious mechanic and learning one project at a time. So forgive the dumb question.
But I had a leak and wanted to change my valve cover gaskets yesterday on my 69 C10 SB. Standard 350 engine and 4 barrel carb. . After opening one I changed and moved on no issue, the 2nd had a milky substance all over one side underneath the valve cover. I cleaned out replaced gasket and put back in. What is the substance? I have seen different answers everywhere I look online. Also. Now my truck is blowing black smoke out and barely idling at all. I didn't mess with anything else yesterday either. Do I have a bad head gasket? Any info is appreciated. Thanks all!
Sonny
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[special-K]

Sounds like coolant in the oil, likely a head gasket. That would make white smoke, so not sure about the black (carbon) smoke. Run the truck till warm and look in the radiator for air bubbles, a sure sign compression is blowing air into the water jacket.

[hamjet]

Another cause this time of year is condensation from the cold temps. I've noticed it on the oil fill cap, and valve covers through the years here in the cold climate. as for the black smoke/ idleing sounds like the choke is stuck. while removing the pass valve cover did you maybe hit the choke stove on the intake,( if thats what you have) and its binding on the choke shaft?? a pic is worth a thousand questions.

[GASoline71]

Do you have a functioning PCV? It will aid in reducing the amount of condensation that can build up in the engine on these cold frosty mornings. One sure fire way to get rid of condensation is to make sure the truck is driven at an extended period of time past full warm up. It's the short trips where the engine barely reaches operating temp and then gets shut off... that then lets the condensation accumulate without being "burned off".

Or... it's a head gasket.

Ditto on checking the choke. A stuck choke will cause all kinds of sooty black smoke and erratic idle. Even if the choke butterfly is only cocked slightly, it can affect the engine.

Gary

[toolboxchev]

Uh oh.

Do not frett my good man, it is fixable, do a coolant system pressure test. That will tell you a lot.

[truckster]

Originally Posted by GASoline71

Do you have a functioning PCV? It will aid in reducing the amount of condensation that can build up in the engine on these cold frosty mornings. One sure fire way to get rid of condensation is to make sure the truck is driven at an extended period of time past full warm up. It's the short trips where the engine barely reaches operating temp and then gets shut off... that then lets the condensation accumulate without being "burned off".
Gary

Ditto on the PCV. If the milky oil was only under the valve cover and not on the dipstick, it's likely you just need to make sure you PCV system is functioning properly and drive it until it warms up.

If the oil on the dipstick is milky, then I'd be worried about a head gasket.

[davepl]

Originally Posted by truckster

If the oil on the dipstick is milky, then I'd be worried about a head gasket.

I'd agree. It's almost certainly water in the oil, the only question is how much and why - and the how much seems to be "not much", which is good. But if its in the pan too, at least more than a skim coat, that'd be bad.