The Stovebolt Site Forums The Shop Area Engine Shop Ol' Roy's Overheating Update

I finally had time to get back on Ol' Roy's overheating issue. I won't re-hash the entire story but have narrowed down the cause (I believe) as either a blockage in the water gallery - probably down by the petcock, and/or hot exhaust gas entering the cooling passages via a head gasket leak.

I used a block test kit to see if hot exhaust gases were entering the water gallery and heating up the coolant. If the Tidy Bowl blue fluid turns yellow as air from the radiator passes through it, it indicates an exhaust leak into the gallery.

Well, the fluid turned green. Nowhere on the box or fluid test kit does it mention green. It only mentions blue for no leak and yellow for leak.

What gives?

I'm of the opinion that any color but blue indicates a contamination of some sort and the only place it can be coming from is the exhaust, right?

No fluid loss is present except when the engine boils over. No water in oil. No steam out the exhaust pipe.

Any ideas on the green fluid?

Well, green frequency is between yellow and blue frequencies of light. Maybe you have a "not much of a" leak.

Bill is correct. The fluid turns green on the way to yellow, so you are getting exhaust gasses in the coolant system.

Oddly, the last time I started the truck and ran it to try and do a flush, it overheated in a matter of minutes just idling.

Today it never got over 180 idling for 45 minutes and I was able to drive it a couple miles with no overheating.

I did, however, observe bubbles in the top of the radiator tank. Air bubbles from sitting for a month with no water in it? Doesn't seem like it.

My phone won't download pics to my computer for some reason I can't post any right now.

OK. I left it for a long time and it never got to yellow but I figured any color that isn't blue isn't good.

Have you pulled plugs to see if any have a “steam cleaned” appearance?

The third test stayed blue for nearly 20 minutes and never changed. Weird.

Yes. I did all that back in July or whenever the boilover occurred. Everything is hunky dory and the truck runs perfectly.

It sounds like a small/intermittent leak. I have seen those a few times and they always progress to catastrophic failure.

I would recommend pulling the head and addressing it sooner than later.

I don`t know much but coolant should be churning at the top of the rad with the
thermostat open and cap off.

If the cooling system is pressurizing before it reaches normal temperature, you have compression/exhaust leaking into the cooling system. Rent a cooling system pressure test kit and with a cold engine and normal water level, attach the pressure gauge/rad cap. Start it and observe the gauge.

I already rented a pressure tester witth 22 different adapters. Unfortunately not a single adapter is made to fit antique cars. By that I mean the standard sized radiator cap used on virtually every vehicle up to the 2000s is too large for any of the fittings supplied in the kit.

Hmmm, is there an alternate route to access the cooling system? Maybe rig up something to tee into a heater hose, radiator hose, unused threaded port? It won't make much difference where in the system you take a pressure reading, just compare cold start pressure to that while it is warming up. Or, fabricate a rubber expansion plug to fit in your radiator opening and drill it to accept a gauge?

Already did that the weekend this happened. Pressurized it to 55psi with water. No water ended up in the cylinders and pressure was never lost in over an hour. Heater core and radiator were removed from the loop.

Plumb the tester into a heater hose or just tap into the drain petcock port (1/4" NPT) and run the engine without pumping up any pressure. If pressure builds up before the engine reaches operating temp, you have a compression/combustion gas leak somewhere.
Jerry

The radiator cap is only 4 pounds. Will a pressure gauge (I assume I can use my fuel pressure/vacuum gauge) on the drain port be enough to tell me?

What would I look for? Any pressure above zero below 180 degrees?

I had a nearly identical issue two years ago. Motor over heating, blowing fluid out of the overflow container. I used the dye test, turned green, just like yours. Got a pressure tester on it, it was leaking a little pressure but hardly much at all.

I ended up pulling the head. The copper head gasket had failed in just one tiny area, and was letting combustion pressure into the cooling system. It was such a small failure, it took time to build up. I had Rebuilt another head (just in case it was a crank in the head).

Put the new head on with a fresh felpro blue gasket. I opted not to use one of my spare copper gaskets and went with a fresh composite gasket. The over heating stopped.

Took the old head back to machine shop, turns out the head, which I rebuilt many years ago was likely the cause of the gasket failure. The machining on the head surface was rougher than what is done today.

Ya, I guess the head/intake/exhaust is going to come off.

While all that is out of the way, I intend to remove the core plugs and petcock and clean out any debris or rust that might be in there.

Where was the leak on your head, Dragsix? Why didn't you use the copper gasket? Do you feel the Felpro blue gsket ios superior? What's it made of?

If I have to have the mating surface of the head machined/planed, can that be done with the valve train in place?

Sure, as long as you are not worried about all of the super fine grit and metal shavings all up in your valve train when they are done milling the head. (My tongue is firmly planted in my cheek of course.)

Yea, take the valves and springs off if you are not going to rebuild the head. Just keep the valves marked. After the head is machined flat, get some blue dykem, valve lapping compound and lap the valves in just to make sure no issues. Then clean clean and clean.

I took a pass on the copper gaskets for a couple of reasons. They are not made any longer and my stash of gaskets are all 30-40 years old. All new of course, but I just felt that it was time to use something fresh. That and I have heard very little to no complaints of failure, so I opted for a fresh blue composite gasket.

While the head is off, clean out the passage for the rocker feed. They can get gummed up and now is a good time to clean it out.

If the head needs to be rebuilt, then there is more involved of course.