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Coolant Pressure
#1423851 Mon Sep 13 2021 05:19 PM
Joined: Jun 2019
Posts: 32
G
'Bolter
Hi I recently acquired a 1951 3100 there was a radiator but wasn’t installed I brought the radiator to a radiator shop to get it cleaned and checked. The shoo stated everything was good but they weren’t to sure about the built in pressure relief valve. Does anyone know what the pressure is to build to. It’s a 235. The pressure relief is built in to the upper tank and has a copper tube soldered to the side of it

Re: Coolant Pressure
Gmetzger #1423857 Mon Sep 13 2021 05:55 PM
Joined: Mar 2010
Posts: 691
B
Curmudgeon
The original 1951 Chevy truck radiator, made by Harrison, did not have a "built-in" pressure relief valve. There is a zero (see below, thanks Tim) pound radiator cap that twists on/off onto the neck on the top radiator tank. Soldered into the neck is a tube that runs down the side of the radiator that allows expanded coolant to escape (overflow) if the radiator is filled too full of coolant (coolant expands with heat). I believe it wasn't until 1954 that a 4 pound pressure cap was used. The old radiators can't stand a lot of pressure so I wouldn't go higher than 4 pounds.

If you do not have an original Harrison radiator, see if you can find identifying numbers or manufacturer. A picture would be nice.

Last edited by buoymaker; Mon Sep 13 2021 06:11 PM.
Re: Coolant Pressure
buoymaker #1423859 Mon Sep 13 2021 06:04 PM
Joined: Sep 2001
Posts: 31,334
Bubba


Tim
1954Advance-Design.com [1954advance-design.com]
1954 3106 Carryall Suburban [stovebolt.com] - part of the family for 49 years
1954 3104 5-window pickup w/Hydra-Matic [1954advance-design.com] - part of the family for 15 years
- If you have to stomp on your foot-pedal starter, either you, or your starter, or your engine, has a problem.
- The 216 and early 235 engines are not "splash oilers" - this is a splash oiler. [chevy.oldcarmanualproject.com]
Re: Coolant Pressure
Gmetzger #1423881 Mon Sep 13 2021 08:51 PM
Joined: Apr 2010
Posts: 323
6
'Bolter
Sounds like you have a GMC radiator with the built in pressure relief in the upper tank.

Re: Coolant Pressure
Gmetzger #1423905 Mon Sep 13 2021 11:50 PM
Joined: Feb 2004
Posts: 23,180
H
'Bolter
All it takes to check that relief valve is an air hose and a pressure regulator. Should you really be dealing with a "radiator" shop where they don't know how to do that?
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Coolant Pressure
Gmetzger #1423958 Tue Sep 14 2021 01:48 PM
Joined: Jun 2019
Posts: 32
G
'Bolter
Thanks for the info the shop stated that the pressure relief was working just that it was active at very low pressure since it is only set at 4lbs that would be normal.

Re: Coolant Pressure
Gmetzger #1423989 Tue Sep 14 2021 05:30 PM
Joined: Feb 2004
Posts: 23,180
H
'Bolter
Since every pound of pressure on a cooling system raises the boiling point 3 degrees F., a #4 pressure relief will raise the boiling point at sea level to 228 degrees F. Most stovebolters would get their lacy drawers in a wad and have fainting spells if their engines ever got that hot!
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!

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