1952 m38 brake master cylinder question

joebuck · Last edited by joebuck on Wed Aug 26, 2020 9:00 am; edited 1 time in total

I gave up on removing the master cap. I am afraid to heat it do to it being cast and don’t know it brake fluid is flammable. Main problem is getting a wrench or vice grips on it tight. Now thinking about unscrewing or trying to the brass vent bushing . But that will take some type of special wrench curved. Only access I have is through the hole in the floor board. Any more suggestions?
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1952 M38

wesk · Posted: Mon Aug 24, 2020 10:44 am Post subject:

Is you floor's little round access plate missing?

That little line is only a vent line that goes to the air cleaner.

joebuck · Posted: Mon Aug 24, 2020 11:04 am Post subject:

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1952 M38

joebuck · Posted: Mon Aug 24, 2020 11:08 am Post subject:

I have the plate, i removed it. I wonder if i should clip the value line going to the air breather and plug the cap? It's going to be a bugger getting my hand back on that inline value nut.
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1952 M38

mdainsd · Member Joined: Oct 20, 2017 Posts: 444

The cap must NOT be plugged, it has to have an opening to the atmosphere for the M/C to work properly.
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'52 Dodge M37, '42 GPW, '48 FrankenJeep CJ2A/M38, '50 CJV-35(U), '51 M38, '42 WC-57 Command Car, '44 WC-51 Weapons , (2) M1941 Sperry 60" Anti-Aircraft Searchlights, John Deere M-gator, '44 White M3A1 Scout Car

joebuck · Posted: Mon Aug 24, 2020 11:36 am Post subject:

dang!
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1952 M38

wesk · Posted: Mon Aug 24, 2020 11:45 am Post subject:

Here are a few options and special tools.

Or simply remove the old cap and vent line and install a vented cap without that 1/8" pipe tap hole like my cap.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php

OKCM38CDN · Posted: Mon Aug 24, 2020 12:08 pm Post subject:

The line attached to the M/C cap is 3/16" vent line, you can remove the vent line from the elbow with a 3/8" wrench, use caution as it may be tight or corroded. Then the cap can be pulled off. It is a tight fit, but a little patience and it will be OK... remember to put the vent line back on after servicing the brakes...
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Hal, KB1ZQ
TSGT, USAF (Ret)
1952 M-38 CDN CAR 52-31313
1952 M-100 Strick #104
1951 Willys Wagon (For Sale)
1954 Willys M38A1 201001205
Tornado Alley
Del City, OK

4x4M38 · Posted: Mon Aug 24, 2020 1:26 pm Post subject:

The one photo looks to be shot through the firewall. Am I off my nut or is there not a banjo fitting on the nose of your master cylinder? You do have brake lines to front and rear, right?

Maybe I’m just not seeing it.
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Brian
1950 M38
MC11481
http://www.willysmjeeps.com/v2/modules.php?set_albumName=album372&op=modload&name=gallery&file=index&include=view_album.php

joebuck · Posted: Tue Aug 25, 2020 7:08 am Post subject:

Thanks guys! I bought a 3/8" wrench and after some hours of letting Liquid wrench do it's job , the vent line was fairly easy to get off. But that master cylinder cap is a bugger to get off..cant budge it.. my have to put a cheetah bar on it
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1952 M38

joebuck · Posted: Thu Aug 27, 2020 1:29 pm Post subject:

i was able to get the brass bushing off the top of cap. i gave up on the cap before i tore something up ! Got a funnel and hose and filled the cylinder to proper level and BAM i got brakes again!! i guess i never had them for last 8 years since i bought the jeep refurbished. They have alot of resistance and really stop the jeep about 1/2 stroke! thanks for the help
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1952 M38

wesk · Posted: Thu Aug 27, 2020 1:40 pm Post subject:

Since you had no brakes it is safe to assume the fluid was empty or low enough to let large amounts of air into the plumbing which means the current pedal you have is still a soft pedal until of course you complete the next step and bleed the air out of the rest of the brake system at each of the four wheel cylinders.
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Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100

Mjeeps photo album: http://www.willysmjeeps.com/v2/modules.php?set_albumName=Wes-Knettle&op=modload&name=gallery&file=index&include=view_album.php


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