VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 1937 chevy master brakes

Hello needing some help with my 1937 master deluxe brake sytem. I cant seem to build presure on brake pedal with first intitial pump. Only after 2nd or 3rd pump will presure build. Ive changed the master cylinder and bleed brakes numerous times. I changed the two front brake wheel cylinders about a year ago so i recently changed the back rear wheel cylinders to see if that corrected problem and it didnt. Should I start to think maybe i recieved a bad master cylinder? All brake lines are good and dont see any leaks ive even adjusted brakes all the way around just to eliminate that. Any suggestions or ideas would be helpful thanks

Sounds like there is air in the lines . Needs more bleeding ?

Adjust the brakes. You have too much play in the shoes. Each pump is moving them closer to the drum.

Are you bleeding the brakes in the correct sequence?longest first which is the left rear, then left front. right rear and then the right front......from my 1939 shop manual. 1937 should be the same.

Ok so i been bleeding from rear left too rear right . So im going to bleed from rear left too front left per chev nuts advise. Tiny ive adjusted each set of brakes too where tire spins 1 1/2 times before stoping . Lots of people suggested this adjustment. Does that sound about right ? Another question i have is how important is bench bleeding a new master cylinder? does brake bleeding take care of this step ? One more thing where the heck do i find the create new forum tab on this site ? I posted this in the new user which i knew was wrong but i couldn’t find the selection forum tab

I am not sure which way the LHD pipes run but my RHD brake pipes run from m/cylinder along r/h frame rail to rear axle making l/h cylinder furthest then r/h cylinder, the next in line is l/h front and lastly is r/h front. Definitely adjust all brakes first.
Tony

If the brakes aren't spongy when they do pump up it's not air in the line. You can bleed until you have no blood and it won't help. Snug up your brake adjustment. I had that exact issue on my 38. I now have rock hard brakes with little pedal travel.

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I agree with Tiny.

Everything you've said indicates your brake shoes being way out of adjustment.
If you haven't set them up yet, you are wasting your time doing anything else.

Check the shop manual for the correct brake adjustment procedure. You have to adjust each of the 8 shoes separately.

You adjust each shoe until there is a slight drag. Then back off just 4 notches.

I also assume that you adjusted the toe-board clearance after you installed the new master cylinder.

Rusty on the 37 setup you cant adjust any toe board clearemce from what i see. The piston comimimg out of master cylinder is not adjustable and everything esle that touches the master cylinder is also not adjustable. Tony thats exactly how my brake lines are running. Im going to follow Tinys advise before any thing futher and start readjusting all the brakes sounds like thtas probablly whats going on. Infelt i adjusted correctly but let me give it one more try . Ill let you all know

Don't forget that Huck brakes require both shoes on each wheel to be adjusted individually. That's two adjustments per wheel. I set mine a bit tighter than others. I adjust until I start to feel friction then back off one click at a time until no friction. That's often just one or two clicks. I don't have a 37 manual, this is the 38 for setting toe board clearance: https://chevy.oldcarmanualproject.com/shop/1938/38csm125.html

If you look at page 89 of the 1937 shop manual it shows how to adjust the toe-board clearance.

There is supposed to be an eccentric bolt in the connection to the master cylinder push rod. Someone might have replaced that with a regular bolt not realizing the significance of that adjustment.

Thank you rusty for that info going to look at that . So this is where im at. i readjusted all brakes seems like i got the correct presure i need on brake pedal. but now when i slam hard on brakes , seems like the front passenger brake cylinder is getting stuck because right after i slam on brakes and relese brake pedal the car starts pulling hard to the right for about 10 to 15 seconds before it stops pulling. Normal braking will not cause any pull only slamming or hard braking. Im almost positive this would be a bad cylinder correct? Or can something else like air or incorrect toe board clearence cause this on only one cylinder? Jus want some one with more experience to advise if i should just change this cylinder or try the bleeding or toe board adjustment that rusty mentioned before any changing is done. Or maybe s bad adjustment on that cylinder?

It could also be a bad brake hose. They often fail on the inside.

Dave

X2 Another possibility is a broken or missing brake shoe return spring.

Ok im on it again .. going to start with looking for that toeboard adjust Rusty mentioned . I think the adjustment is ok considering i was able to get the pressure but im curious to see what rusty was talking about. Then im going to change out that return spring i have a couple spare ones so that should be a real easy isolation. If that dont do it ill get hose changed out … im exhausted haha … thanks again for all the advise

The toe board clearance is necessary to make sure that the piston in the master cylinder returns fully to the “home” position. That position means that the return hole from the brake line is open so fluid can flow freely back into the reservoir.

In simple terms you should be able to move the brake pedal a very small amount before the piston starts to move.

While you have the brakes uncovered it is easy to check the cylinders are free. With the car pulling to the right there are 2 possibilities (a) a right hand piston is initially sticking and then releasing or a weak spring or (b) left cylinder is stuck in the released position and not working at all.
Tony

Finally had the time to jump back on this . Bad return spring on right front brakes. What a job this turned out to be. Thanks for all the help.

Glad you got it figured out.