Pre-war (up to 1942) 1940 Lasalle radiator cap

[Ben Medlock]

I'm noticing that when I top off my radiator, go for a drive then shut it off in the drive way afterwards that the overflow has water coming out. So, I'm wandering if the radiator cap should be replaced. The rubber seat looks Ok but it is an old cap. The cap is stamped #7 so I assume that means it opens when the pressure builds up to 7 psi. Questions and thoughts:

1- Being that its an old cap, maybe the spring is weak

2- Is the 7# cap the right cap

3- Even if 7# is the right cap, should I go with a higher setting, and if so, what setting is too high?

BTW... this car has a 346 engine and NOT the 322 as it should. If that makes a difference.

[J. Russo]

This may help......

https://forums.cadillaclasalle.club/index.php?topic=154304.msg423148#msg423148

https://forums.cadillaclasalle.club/index.php?topic=138020.msg315988#msg315988

https://www.ebay.com/p/1626565725

[Ben Medlock]

Looks like a 7# cap is the correct one.  Thanks

[LaSalle5019]

7 lb cap is correct. 346 vs 322 doesn't make any difference. If you fill the radiator up close to full it will always purge out coolant from the overflow. The fairly high volume of coolant in these cars expands considerably with temperature and, since there is no coolant recovery system, the cooling system will tend to find a happy level. On my 1939 LaSalle, that level is about 3 inches below from the flange on the neck where the rubber seal on the cap seals.

Looking down in my tank, there is a support flange and you can see the fluid just covers it.

[Ben Medlock]

Thanks for that help. I did order a new 7# cap but good to know that the coolant level will not stay topped off.