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overheating in a 39 special

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<TABLE style="TABLE-LAYOUT: fixed" cellSpacing=0 cellPadding=0 width="100%" align=center height="100%"><TBODY><TR><TD vAlign=bottom width=140 align=left></TD><TD style="WHITE-SPACE: nowrap; OVERFLOW: hidden" vAlign=top><TABLE style="WHITE-SPACE: normal" cellSpacing=0 cellPadding=0 width="100%"><TBODY><TR><TD height=30></TD></TR><TR><TD> I inherited a 39 special from my father when he passed. He had rebuilt the whole car and drove it frequently before he died. The car sat for about 4 years however with a little elbow grease it started and ran fine. I'd take it out for our local memorial day parades and drive it every so often on nice days. He is the problem last year the car overheated during a parade. I stopped ,let it cool down filled it back up with 50/50 water and anti freeze to bring it back home. it overheated again.. I thought maybe I blew the headgasket so I replaced it. Now, The car will run fine all day long at an idle and not over heat if you drive it or keep it at a high idle 1200 rpm the temp gage goes to 220 and the radiator starts to push out steam and water out of the overflow. If I leave it at this speed it will overheat and puke every thing out of the radiator.

I have taken the nose off and I put a radiator from a 40 in a frame secured it and ran the motor same result. I have replaced the following new water pump thermostat and checked out the lower hose to make sure it wasn't collasping

I have a digital infra red thermometer and when I check the block it stays consistant at 185/ 190 degrees the radiator stays at 160/170 at the bottom and goes up to 190/210 at the top

the car has a bypass hose about 18' long in place of the heater core lines

I remember my dad telling me that these cars had an overheating problem due to the grill design However now I have the nose off I can feel the air passing thru the front of the radiator still it overheats

any thoughts on what I should try next?

It seems the radiator gets hotter then the motor it seems like it comes in in spurts when it starts to run hot kind of puffin out the overfloe tube

I will change the water pump again flush ou tthe radiator and block again I will put in a new thermostat and new radiator cap

I do not see any white smoke coming out of the exhaust or out of the crankcase breather tube

any thoughts on what the heck I am missing? any special tricks? any where I can turn to/for help

thank you

Kurt Bober

294 haddam qtr rd




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Welcome to the 39 Buick world !

See this thread http://forums.aaca.org/f165/boiled-39-anyone-280470.html

I suggest you remove or disguise your email address to stop web scannners (--> junk mail). Also very few people put there home address in a public forum. You can be contacted via private message thru your user name.

Edited by 1939_buick (see edit history)
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What about hot compression gasses getting into the water? Any way you can plug the overflow and put your hand on the filler to see if there is pressure being generated?

Since the block is staying cool, it may be a possibility that the very hot compression gasses are heating the water.

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Sort of........ but there could be other ways for compression gasses to get into the cooling.

A crack or eroded head. I would think a bad head gasket would get worse (bigger gap) and when that happens, water would leak back into the cylinder and you could detect that.

Something like a crack might expand with heat and allow the compression gas which is under higher psi than static water, to get into the cooling lines. When the engine cools, the crack would close and little or no water would be in the cylinder.

The test to see if you are getting pressure or CO2 in the cooling is pretty easy.

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I believe in doing the cheap fix first....

First check the bottom hose from the radiator to see if it will collapse easily. This will cause cavitation & damage the water pump too. New bottom hoses have a spiral wire inside to keep it from collapsing. If you can squeeze it together with your fingers, replace it.

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If the lower hose, like you said, is all good then first just check all the vital signs, make sure everything is right. Timing, fuel, etc. Make sure it's not too rich or too lean, carb is alright...a small issue but nothing wrong with putting everything equal. I assume it does start and run smooth and sound right? If yes then I'd argue the timing is probably within range, but check it anyway.

Definitely do a compression test, crank it with all spark plugs out, engine already warmed up, wide open throttle while cranking with the compression gauge hooked up.

Was the engine rebuilt? Entirely gone through, paint stripped off, hot tanked and cleaned out? I was utterly shocked honestly to not find tons of crap in my 248 when I had the head off this winter, but they say buildup likes to occur in the back of these engines because they are mounted such that they tilt backward just a little bit. Might have plugged passages. Do you *KNOW* the radiator is good? I learned that lesson, I thought it flowed pretty well, filling it and letting water run out the bottom, it came out fast. But clearly that's a poor test....it must have had too many cores plugged because I threw down the stinkin' $110 and had it boiled out, a couple small leaks they found patched, and painted. That was the silver bullet. Granted this is a '38 not '39 with the grille problem (which is not a myth, the airflow is restricted and doesn't help but doesn't guarantee brutal overheating like you're experiencing in any conditions.

Youre in CT, we've been having some hot days recently but up until today here in NY anyway it hasnt been 95-100 degrees or more. What I mean to say....is that don't let someone tell you that "all those old straight eights always ran hot". I heard that from soooo many guys at car shows when my rig was blowing up. And not to slam them, they are all good people but these things get passed on and on and circluate like any old wives' tale. The cooling system on a late 30's Buick I-8 is AMPLE to take care of the engine's heat output. Anything below a hot humid 80 degree or higher summer day and my '38 won't go above 160. A cool 50 degree evening, it wont go past 130. All I know is what the gauge says, I aint lyin!!! And Ive done nothing like change the pulley size or go to a bigger more-bladed fan or anything. 100% stock cooling system, 91000 miles young. ;) Just saying that it should be able to take care of itself....

I think it's the radiator. The cooling system is not very complicated, only so many things that can go wrong. Naturally make sure you installed the thermostat right, what temperature was it? If it wasnt a 160 degree, get a 160 degree one. Test it in a pot of boiling water on the stove, make sure it works as it should. I've had a bad brand new thermostat, that wasn't fun to find out!

Edited by ZondaC12 (see edit history)
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