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Bob, my first Buick was a 1940 Special back when it was just a used car. 1954, to be exact.


  If the coolant continues to heat past the thermostat temp while driving, the radiator is almost certainly partially plugged. NOTHING will clean it except to remove and have it rodded out. Everything else is pi++ing in the wind.  Spray the radiator with a garden hose next time it is run, after coming up to temp. The part that STAYS wet after a few minutes is plugged.



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Ben's check works well and I used it on my '40 LTD.

Did you do the standard bypass valve fix yet ?

Just below the thermostat is the bypass valve housing, where the big hose comes up from the bottom of the radiator.

Pull that housing and discard what ever is left of the valve. You may have to grind out the brass shaft, if it's still there.

Tap in a frost plug of the correct size, and drill a 5/16" hole in the center.

I did this fix, as was recommended here on the forums, after fighting overheating for about 3 years, and it fixed it immediately.

This fix lets the hot water out of the head, instead of being "overpowered" by the water coming up from the radiator, as it's being sucked into the pump.


Mike in Colorado

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Ok, have a question for Flyer15015, i have took the bypass valve housing out and see the brass valve and shaft inside the housing, once out i dont understand what you are saying about taping a frost plug drilling a 5/16th hole in the center?, Hope you can reply to this, thanks Bob

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  If you go to the 1936-1938 Club website they have become custodians of the old 1937-1938 newsletters and an index. You can find a few articles and descriptions there. I've never felt the need to do this with my 1937.

 I believe this is what the finished product is supposed to look like;


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This is how I did my ‘38 Special.


Used all the bits from standard and  added some brass tube from K&S Engineering (hobby shops keep it) to prevent the valve moving against the spring.


The tube goes over the centre brass rod and keeps the first brass cup from seating on the cast housing. You can see this better in the second picture.


This keeps a restriction on the flow yet allows it to bypass until it reaches the thermostat. So far it keeps good operating temperature but I also have the benefit of a recorded radiator and rebuilt water pump.


used a brass split pin before the install too!

Rodney 😀😀😀😀😀😀😀😀




Edited by rodneybeauchamp (see edit history)
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