250 losing coolant but no noticable leaks

A friend has a mid 70s 250 that is losing coolant with no noticeable leaks and no coolant smell from the exhaust,put a pressure tester on the system and even running its losing pressure so could it have a head gasket starting to go.

bet its a cracked head, time to pull it before anymore damage happens jmo

bad head gasket, cracked head, cracked block, bad radiator cap, leaking freeze plug, leaky hose, leaky heater core, leaky radiator are all places to start. first thing to do is check the oil to see if the level has gone up. also pull the valve cover and see if the oil in the head looks like a milkshake, or is still oil looking.

I went over it and looked at everything including the heater core and nothing noticeable,I did tighten all the hose clamps as a couple were loose but no signs of leakage on the hoses. The coolant loss started quickly and it still runs like a swiss watch.

If it's not in the oil it's either got to be going out of the exhaust, out the overflow, or hissing out from a pin hole somewhere in the radiator, heater core or somewhere else in the system. When the engine is good and hot and you shut it down, listen and smell, anything?

Can not smell anything under the hood.

& no "white smoke" out the tail pipe?

Gotta use those senses (eyes, ears, nose, wave of the hand, thank goodness this 1 don't take taste).

Nothing noticeable out the tailpipe.

55sunliner":32ibhjry said:

A friend has a mid 70s 250 that is losing coolant with no noticeable leaks and no coolant smell from the exhaust,put a pressure tester on the system and even running its losing pressure so could it have a head gasket starting to go.

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yes, no doubt…
how much, how often?
leave it pumped up over nite (pressure tester) & back to the eyes, ears, nose, hand,
the guys listed all I could think of - gotta B one or more of them.
Even a large paper under motor can show something...

thank goodness this 1 don't take taste).

I used to work with an old timer, he would taste the oil on the dipstick to see if it was sweet. That would tell him if there was anti freeze in the oil.
When I say "old timer", I mean it. He used to cut school as a kid and take a boat out the rum runners offshore and then smuggle it back for $ !
DannyG

Hi, I would check your compression. A blown head gasket is possible. Look closely at your spark plugs, the bad cylinder(s) will likely be very white or very clean. If that is the case I would think about a valve job. The seats are hammered, the valves burnt and crusty, tips mushroomed, seals hardened, guides worn, springs tired. Make sure to check for flatness on the bottom and on the exhaust flange. I have seen engines drink a lot of coolant with no sign of smoke or smell. UView makes a tester where you can sample the coolant for exhaust, #560000. You might see your cooling system hoses blowing up like balloons. It depends on where the head gasket lets go. It may be between 2 cylinders, but that may not result in coolant loss, it may be between the cylinder and water jacket (coolant seeps into cylinder). A cooling system pressure tester may help in the diagnosis. If you pressurize with the spark plugs out you may get coolant out of the bad cylinder. Your engine may hold pressure when cold. but leak when warmed up, metal expands=holes get bigger. Hope that helps B RON CO. Still workin' on it!

guys oil floats on water / antifreeze. pull drain plug........................... when engine is cold. or get oil sample done. if it was me and alls been checked externally I,d open it up/ you could also use a bore scope down the plug holes.

BCOWANWHEELS":31yucdt9 said:

guys oil floats on water / antifreeze. pull drain plug........................... when engine is cold. or get oil sample done. if it was me and alls been checked externally I,d open it up/ you could also use a bore scope down the plug holes.

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that is why i suggested checking the oil to see if it has risen.

Oil was fine and when i talked to him today there was no mention of filling the radiator again so it might have been a clamp loose enough to force coolant out on the highway but not leak while sitting.

55sunliner":wvhh8hd4 said:

Oil was fine and when i talked to him today there was no mention of filling the radiator again so it might have been a clamp loose enough to force coolant out on the highway but not leak while sitting.

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its also possible that there was a bubble in the system some where that needed to bleed out as well.

:x :mrgreen: