Disappearing coolant

[crazyal]

I would replace the radiator cap. You would think that the overflow bottle would catch anything it lets out but it's cheap and it's the one part of the system that you don't test when you do a pressure test.

 

[2458n]

Old Datsun truck did the same thing. Head was warpped and it was using very small amounts of Prestone. Just disappeared out the muffler. Took it to a shop that made their living fixing this problem. Have you ever had to run it hot for any reason?

 

[Coyote machine]

It's likely being burnt in combustion and being vaporized as it goes through the exhaust. Small amounts might not show up as smoke.

 

[Egon]

Pull the head. If the carbon build up in the cylinders is pretty well gone you know there is coolant getting in somewhere. Might have to take it to a shop for the tests to find the crack.

 

[RaydaKub]

So if you run for 2 hours, does it drop 3/4 to a full inch? Does it ever drop below the core?

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[flusher]

Check the exterior sides of the engine block carefully. Could be a hairline crack in the thinner parts of the casting where the coolant passages are located.

When I had the Hercules engine (4 cyl, gas, 27 hp) rebuilt for my 1951 Minneapolis Moline BF tractor, we found such a crack. The engine guy was able to braze it OK.

The block on my Farmall Super A has a similar crack that the previous owner repaired with epoxy.

Good luck.

 

[arrow]

I would replace the radiator cap. You would think that the overflow bottle would catch anything it lets out but it's cheap and it's the one part of the system that you don't test when you do a pressure test.

Tested cap and is fine. Holds a steady 13lbs after 28 years. The longer I run it, the farther down the coolant goes so I'm guessing its a slightly cracked head at the exhaust. Here's a $700 bill for a new head I didn't want.

 

[arrow]

So if you run for 2 hours, does it drop 3/4 to a full inch? Does it ever drop below the core?

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Yes. Always catch it in time before that happens.

 

[Soundguy]

i type on a tablet.. so get plenty of misspellings.

word was clean.

normal on a good head gasket or other leak that is going into the combustion chamber.. you get steam cleaned parts.

plugs on gassers.. and possibly injectors and gp's on diesels.

at 1/4" loss.. it simply maynot be enough.

with no steam in the stack.. no external leaks.. and no oil in the water and water in the oil. it's either boiling off thru the cooling system.. or going out the tailpipe in non sufficient amounts to steam.

i'm not a mechanic.. but those have been my observations over the years...

 

[tjcapt]

I would agree with the cracked head and its burning out the exhaust. You could purchase some fluorescent die and put it in the coolant, a black light inspection should then show where it is going.