Let the pictures do the talking. Looks like water is collecting, but the rocker assy. and the actual oil in the pan are all water free.

Regularly driven truck, never sits.

 

That is what an engine looks like when it has not been up to operating temperature. It takes heat to boil that moisture out. Are you running a thermostat? Do you take the truck out and drive it a while? Around the block or just down the road won't do it. More prevalent in cold weather.

 

Not up to operating temp often enough just as raytasch suggested

 

What they said ^^^^. It's condensation forming from a warm engine to a cold valve cover. Also, check your PCV valve if equipped. Do you have a PCV valve on the valve cover?

 

This truck is driven daily, 10 miles to work, with highways often involved. I have two temp gauges: one sender positioned in the stock location at the rear end of the head; the other is in a home-made water neck positioned between the thermostat housing and the radiator.

Thermostat is a 180ºF unit.

Temp readings are like clockwork: temp at rear of head during normal warmed operation is 160º.

Temp at waterneck is 180-190º, generally.

Yes it does, and that slime has been present for the last 2-3 oil changes, but I never noticed it before then. Doesn't mean it wasn't there.


I have--since day one after engine rebuild and installation--had a "disappearing coolant" mystery: coolant regualarly needs topping off, but I have no considerable leaks. I have thought it was a slow head gasket leak, but never did anything about it after not finding any water in the oil.

Maybe this is where it goes. This is also the first time I've had the cover off in 15k+ miles.


I also found a surprising amount of black sludge on the opposite surface on the head. I think I'm going to run this oil(brand new today) for 1000-1500 miles, and then change it, and do that once more thereafter. After those 3000 miles I'll tear the valve cover off once again to inspect.



Thank you very much everyone.

 

Question about valve covers.... do you need a new gasket every time you take off and reinstall a valve cover?

 

It may be a good time to add some sealant (Bars-Leak?) to the cooling system.
If you are having a coolant mystery.
...Terry

 

I have a newer car that has an oil temperature gauge from the factory. It is really surprising to me how long it takes the oil to get to temperature. At least 15 minutes after the water temp is at setpoint, in constant driving.

From what I see your oil is getting warm enough to drive off water vapor, but not long enough. Maybe once a week take it for a longer drive?

I think if you were getting antifreeze into the oil it would be obvious, it would be all over the rockers.

 

I was told as a kid this stuff is a band aid mess that doesn't really help, this won't hurt my engine in the long run will it? Maybe I oughta replace the darn head gasket.

This is a fair point. Next time the engine is out, I'm installing a bung for an oil temp gauge.

 

An engine won't reach full thermal equilibrium until it has operated for about twenty minutes under load, and the thermostat has cycled at least five or six times. On a carbureted engine consider 5" to 7" of vacuum a load.
Since you stated the possibility of a coolant leak but no visual signs of one, there are only two places the coolant can disappear to: 1) Out the exhaust; casting crack or head gasket, 2) Directly to the atmosphere; either from a casting crack, blown seal or leaky hose. Do you have a coolant recovery reservoir installed? You can get those combustion gas testers for cooling systems at NAPA or other parts houses.

 

Electric sending unit as a drain plug.

 

^^That is not a bad idea, never heard of that. Thanks

 

Abe to answer your question, No.

OP, I say you have a slight leak of water/coolant into your engine, that is more than just condensation.

 

I agree with the others - that mess is normally from condensation not getting burnt off in a hot engine. But when you couple that with slow, regular coolant loss, it could very well indicate an internal leak of coolant. A surefire way to check for this without tearing things apart is to run a pressure test. Most big box auto part stores will loan or rent you the pressure test kit. Set it up, pump some pressure in, and walk away for an hour. The gauge shouldn't drop at all or very little. Just be careful not to go overboard on applied pressure. These old systems don't run much to begin with. I like to warm the engine up with the radiator cap loose or off before I run the test in case there is a leak that only opens up when it gets warm.

 

I have--since day one after engine rebuild and installation--had a "disappearing coolant" mystery: coolant regualarly needs topping off, but I have no considerable leaks. I have thought it was a slow head gasket leak, but never did anything about it after not finding any water in the oil.

I went back and read this addition, could be significant. As someone asked, are you running a recovery tank? These trucks will throw coolant out, usually down a couple inches as measured in the top tank. As others have mentioned, it takes a bit of work to get these things hot enough to boil all the moisture out of the engine. A ten mile easy drive is not much work for one of these trucks.
It sounds like you have a good running engine, we need to get rid of that excessive moisture. Have you considered a pressure test on the system, as suggested? How about an oil analysis? Either test will show up a coolant leak. Frequent oil changes?