Farm Equipment - Radiator cap For B?

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Radiator cap For B?

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=181000
Printed Date: 22 May 2025 at 11:25pm
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Topic: Radiator cap For B?

Posted By: mdm1
Subject: Radiator cap For B?
Date Posted: 05 Jun 2021 at 12:01pm

My 1939 B popped a free plug. I replaced the radiator on this tractor last fall. I really don't what it had for a cap. Is it possible the cap is wrong and it build up to much pressure and forced out the plug? The pugs are relatively new. What should I use for a cap on that tractor? Do I understand right this is a non pressurized system. Just looking for a cause!

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Everything is impossible until someone does it! WD45-trip loader 1947 c w/woods belly mower, 1939 B, #3 sickle mower 1944 B, 2 1948 G's. Misc other equipment that my wife calls JUNK!

Replies:

Posted By: Boss Man
Date Posted: 05 Jun 2021 at 1:11pm

The same plugs are used on cars and tractors with 15 lbs systems. I would say the plug was improperly installed. Might have been tweaked a little from not being driven straight in or not having the right tool. Dont remember for sure but think its a 5 or 7 lbs system. Better chance of blowing a hose or seam on the radiator than popping a plug.

Posted By: NICKMI
Date Posted: 05 Jun 2021 at 6:31pm

I believe the older ones were not pressurized our 39 uses the same cap for the fuel tank and radiator

Posted By: steve(ill)
Date Posted: 05 Jun 2021 at 10:35pm

the original EARLY Bs did not have a pressurized cap... Later they did.. You can install a low pressure cap on any of them.. I have a 1940 and put a 7 psi cap on it.

Like BOSS said, a 14 psi cap should not effect the plug... But i would suggest a 5-7 psi cap.

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Like them all, but love the "B"s.

Posted By: 1939Dodge
Date Posted: 06 Jun 2021 at 9:51am

The 39s had a vented gas and radiator cap. There is a little hole in the cap.

Posted By: HudCo
Date Posted: 06 Jun 2021 at 10:08am

80 year old frost plug,? over heated once, frooze once?

Posted By: Gary
Date Posted: 06 Jun 2021 at 12:32pm

He said the Pugs are relatively new.

G

Posted By: mdm1
Date Posted: 06 Jun 2021 at 1:38pm

Plugs were put in 2 years ago when the head was redone! Never froze or overheated. Just looking to avoid it in the future. I guess just one of those things that happen. Had an old plug measured and maybe it was a tad small.

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Everything is impossible until someone does it! WD45-trip loader 1947 c w/woods belly mower, 1939 B, #3 sickle mower 1944 B, 2 1948 G's. Misc other equipment that my wife calls JUNK!

Posted By: Ted J
Date Posted: 14 Jun 2021 at 4:47pm

Probably that's what happened Mike. You should have measured the hole. Also could have been the thickness in the plugs too. That would make a difference too. HTHs

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"Allis-Express"
19?? WC / 1941 C / 1952 CA / 1956 WD45 / 1957 WD45 / 1958 D-17

Posted By: steve(ill)
Date Posted: 14 Jun 2021 at 5:30pm

sometimes i turn the plug upside down and smack the flat side.. Spreads the flare out a few thousands for a better PRESS.

to go along with that, during INSTALL, you should use a socket that just fits inside the plug and smack them in... If you use a 1/2 inch rod or similar, you can BELL the center inward and make the OD slightly smaller - less press.

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Like them all, but love the "B"s.

Posted By: mdm1
Date Posted: 14 Jun 2021 at 6:50pm

Got back up to the cabin today and pull started the B. Drove it around and got it up to temp. No leaks, anti freeze level didn't change and no smoke. I think I am good to go. I put this one in with a bearing driver. The cap is a pressurized cap. The old cap wouldn't fit the new radiator that I put on it.

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Everything is impossible until someone does it! WD45-trip loader 1947 c w/woods belly mower, 1939 B, #3 sickle mower 1944 B, 2 1948 G's. Misc other equipment that my wife calls JUNK!