Sludge in coolant, high pressure

[MySons68C20]

Originally Posted by dmjlambert

That is weird. pour that sludge water in a clear glass and come back and look at it in a week or so and see if it separates into water with oil on the top. I'm sorry to hear you're having this trouble on a new engine.

That is a great idea!

[Steeveedee]

I got a face full of black coolant when a vehicle was seriously overheating and I popped the cap. The cap was partially loose and I didn't notice, so when I started to turn it, the coolant spooged. Fortunately I had the radiator water gun in my hand and could do an immediate rinse/cooldown. This could just be from serious overheating? What do the radiator hoses look like inside?

[70STOVEBOLT]

If it was oil, it should look like a chocolate milkshake and not black.

[guyryan100]

I've got some brown milkshake evidence too, in the overflow reservoir. I think I've decided to do a detailed cleanout of the coolant passages, put an inspection camera through it to try to try to spot anything in the block, and then just replace all the gaskets and hoses and see what happens. If there is somehow a hairline crack between an oil and water passage in the bowels of the block, not something I could fix anyway. But hopefully it was a gasket issue. If not, I may just have an oil-cooled engine.

[slikside]

A quick way to determine if you have coolant in your oil, although this will be harder with your intake and a head removed...

Run the engine until it's at temp, and the exhaust manifolds are HOT.

Pull the dipstick and let a few drops of oil land on the exhaust manifold. If you only have oil there, it will just sit and smoke, but if there's water/coolant in the oil, it will sizzle and boil til the liquid is evaporated.

It's truly amazing what you can remember from high school auto shop some 40+ years ago. Just don't ask me about day before yesterday!LOL!

[LNP]

Through the years I worked in the garage we just put the vehicle in a bay let it sit for a while then drain the oil. If theres water/coolant in the oil then it will come out before the oil. Easy to spot that way.

[70STOVEBOLT]

Please post the results of your findings. It may help someone else in the future.

[guyryan100]

Yesterday I flushed each side of the block, both sides took about 15 gallons of water to get water I could see sunlight through. My approach was to pour water in until full (about .75 gallons) and pump it out with a small utility pump I have in small batches, so I could monitor its color. I have relatively clear water now, but there was quite a lot of sludge in both sides.

In my analysis, for this to have leaked in from the head gasket or above is unlikely - there is no pressurized oil this high, no oil flows through head gaskets or the intake manifold, so oil would have to have leaked in with only gravity pressure - probably through a head bolt from the top of the head. I think this is impossible without coolant, under pressure, leaking into the oil in return. There is no coolant in the oil. Even when I open the oil drain plug, brown oil is the first thing out. I sampled the first pint of oil from the drain plug and it has no water.

This tells me oil is entering from the pressurized oil galleries, which don't have gaskets other means I can service them.

I'm considering a test of sealing off the block from the top with a rubber gasket rectangle and a 1x8 board bolted onto the head with thread-sealed bolts, and then adding pressure via the 1/4" NPT drain plug - connecting a pressure gauge and my compressor there to put some coolant under pressure. Perhaps one side would reveal a leak into the oil, which I could observe via a drop in pressure and possibly water coming out of the open drain plug.

This would tell me if I do have a leak, and on what side it is. The block would not have heat, that's the only gap I can think of in my plan, hiding the leak if its heat dependent. But I think in this test since there are no permanent gaskets or rubber hoses involved, I should be ok to put the system under higher pressure as a test - possibly up to 50 psi like the oil would be.

Thoughts?

[dmjlambert]

Are there places where non-pressurized oil pools on a problem gasket, where the pooled oil could be sucked into the coolant when the engine is cooling down? The coolant passages would have vacuum while the overflow coolant is being drawn back into the radiator. Just a thought.

[guyryan100]

Yes dmjlambert that's a good point. Oil sits on top of the threads of several head bolts, blocked out of the coolant only by thread sealant. And the bolt holes are not sealed by the gasket so that same oil would sit on top of the gasket adjacent to sealed water ports. Vacuum in the cooling system could pull that in. I believe if that were happening, positive cool