Radiator Cap Question

[dpcd67]

Will a 7 pound radiator cap cause the lower radiator hose to blow off? Twice?
I was sold an "original cap for an M38" and I was too stupid to notice the 7 on it instead of a 4. And I should have noticed the chain loop but I didn't.
Stupid mistake.

[artificer]

No.
I always ran my MB's from 1960's to my last one with 7# caps. No problem.
Pressure test the cooling system with no cap on the radiator up to 8 or 9# to check for leaks.
Suggest the cap may be the problem.
Pressure test it to see what pressure it is actually cracking @.

[dpcd67]

ok; I have the pressure gauges but no adaptor; so I am going to replace it with a 4 pound cap anyway as it is obviously not working.

[Joe Gopan]

4# is best, the MB/GPW, M-38, and M-38A1 were all designed with a 4# Pressure system. As for the hose coming apart, did you apply some sort of gasket cement to the inside of the hose? It's a no, no.
Keep them original-less chance for trouble.

FYI, the pressure caps used on these 4 Jeeps all interchange.

[dpcd67]

Oops; I used Permatex on everything on this engine, not sure why. I am not looking too good on this one.

[Joe Gopan]

You will encounter instructions to apply gasket cement in some manuals, amd I believe in a WWII TM, but it is not foolproof and the gasket sealer will act as a lubricant.

[dpcd67]

That it did; and the second time (today) I had tightened the clamp tighter than ever. First time (yesterday) was normal tightness.

[artificer]

Correct about acting as a lubricant.
Over-tighten ruins hoses.

[dpcd67]

There is still something else going on as this is the first time I ever had a radiator hose pop off (from the water pump) no matter how I installed it. And I have put many of them on my restorations. Like you said, it must be the cap. Which I will replace.

[W. Winget]

Has the lower radiator output been deformed by overclamping, resulting in a tapered pipe which will shoot off any rubber hose you put in it?
V/R W Winget

[dpcd67]

It came off the water pump. I'll check and see if the iron is deformed.
(That is a joke; I know some guys do not do humor.)

[Joe Gopan]

Not so sure about the radiator connections deforming, but any 5/8" heater hoses that have sealer are more apt to slide off. (Some of you do have heaters)
The repro 1-1/2" Hose Clamps of today do not clamp as well of the OEM of yeaseryear. One can recognize the original 40's Hose Clamps by the shape of the Fillister Head Screws, the repros are usually round head slotted screws.

[dpcd67]

Yep I have the Hunter Heater and you will be pleased to note that I did not use any sealer on those hoses!