1952 m38 brake master cylinder question

joebuck · Post by **joebuck** » Mon Aug 24, 2020 9:37 am

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?

Post by **wesk** » Mon Aug 24, 2020 10:44 am

Is you floor's little round access plate missing?

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

what size is that but on the back

I assume you mean the square raised portion of the cap which gives you a way to use and open end wrench or channel lock pliers on the cap?

joebuck · Post by **joebuck** » Mon Aug 24, 2020 11:04 am

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joebuck · Post by **joebuck** » Mon Aug 24, 2020 11:08 am

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.

mdainsd · Post by **mdainsd** » Mon Aug 24, 2020 11:35 am

The cap must NOT be plugged, it has to have an opening to the atmosphere for the M/C to work properly.

joebuck · Post by **joebuck** » Mon Aug 24, 2020 11:36 am

dang!

Post by **wesk** » Mon Aug 24, 2020 11:45 am

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.

OKCM38CDN · Post by **OKCM38CDN** » Mon Aug 24, 2020 12:08 pm

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...

4x4M38 · Post by **4x4M38** » Mon Aug 24, 2020 1:26 pm

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.

joebuck · Post by **joebuck** » Tue Aug 25, 2020 7:08 am

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

joebuck · Post by **joebuck** » Thu Aug 27, 2020 1:29 pm

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

Post by **wesk** » Thu Aug 27, 2020 1:40 pm

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.