The Stovebolt Site Forums The Shop Area Driveline 1946 Chevy 1/2Ton - Brake Adjustment

Hey guys, I finally got my '46 back on the road and completed two test drives. When I returned on this last drive I could not push or roll the truck once in the garage. E-brake was off. I probable adjusted the brakes to tight to start with, so I backed off the adjustment and followed the shop manual. All four wheels were spinning. I hopped in the cab and pushed on the brake pedal a few times and it is stiff. Then, I went to spin the front wheels and no go - they are tight again. I re-adjusted both fronts and then pushed on the brake pedal and the same thing, wheel is very tough to spin. Back wheels seem to spin OK. Do you think this is a brake master cylinder issue? Maybe the master cylinder is not releasing the pressure? My brake pedal is very stiff from the start. No inch of free play - feels like it's pushing hard right from the start. I'm going to let it sit for an hour and try to spin the front tires again to see it maybe there will be a pressure loss. Any ideas are very much appreciated.

Note: I am using the original master cylinder. I cleaned it, honed it and installed a new rebuild kit.

Thanks Dan! I'll go check that right now! Yes - the pedal is solid right at the top.

Have you replaced the front rubber hoses .I had a car that built up pressure and it was from the rubber hose they collapse inside and you can push fluid when you step on the brakes but the fluid won’t release from the collapsed hose. There are a hose can also look like new on the outside .

All new hoses and brake lines Kevin. I'm trying to adjust the clevis, but if I go too loose the brake light comes on. I can adjust it so it's 1/4 inch from the floor board, but the front wheels get hard to rotate after I press on the brake pedal and release.

I'm going to loosen both fronts so that the wheels spin without any drag, then step on the brake pedal a few times and see if the fronts continue to spin freely.

I just loosen both fronts so they spin freely. Then, I stepped on the brake pedal a few times and checked to see if the wheels would spin - NOPE. I think I'll disconnect the clevis next, to see if that releases the front drums and let them spin.

John - There's one other possibility that may be involved. The below screenshot is from a 1947 Chevy Truck Shop Manual, which is still applicable in your case as the Huck brake system remains the same. There is a possibility that your master cylinder has an obstruction in the compensating port which is preventing fluid return to the main cylinder.

PS - This page covers checking the clearance for the compensating port in the MC.

I just remove the clevis and the front brakes are still hard to rotate. Dan, It looks like I'll be removing the brake master cylinder. Hindsight - Maybe this is one of those parts I should have bought new and not use an old part? It looked OK when I rebuilt it. Oh well.

Looking at your LINK and this is something I should be able to check when I get the MC removed. Thanks again Dan!

Did you rebuild the master cylinder? If not, you can do so or buy a new one. Save the original to rebuild later.

I installed a Dynamic Friction mc from Rock Auto 5 years ago and its working fine. I think it was less than $40.

Yes - I did install a rebuild kit. I will remove the MC later today and see if there's anything obvious that is keeping it from working properly. After sitting over night, the front wheels do turn easier this morning.

Note: I just looked at those Dynamic Friction master cylinders and they have the mounting bolts on the side. My MC has the mounting bolts pointing down.

Interesting. I see they're all incorrect. Could an L bracket be fashioned to utilize one of the later design?

Dan, I don't want to label you a "Genius" until after testing. But, I got my MC on the bench and noticed the bypass hole is completely plugged. I didn't even know there was another hole in there. I took a pick and opened it up. I just got it installed, so I'll go around to each corner and adjust the brakes from scratch. Then I'll get the brake lines bled and try another test drive.

I'm hoping this was the issue - and it probably was. Thanks for all the suggestions guys!

John - I'm going to jump the gun a little and say WOOHOO!!!

I'll wait to hear your results, but I'm thinking you're going to be pleased.

I am lurking here, and picking up a lot of good input!
I am (slowly) getting closer to completing the resurrection of the brakes on my project.
Thanks!

Finally had a friend show up and I got the brakes bled. Pedal feels so much better. It goes down an inch or so before feeling pressure starts and afterwards I can push the truck back/forth in the garage. I will test drive tomorrow morning.

I looked in the dictionary for the definition of "genius" and it had a picture of Dan's avatar. 🙂 I went for a drive today and the brakes worked as they should. I now know more about brake master cylinders then I knew yesterday!

All you have to do is take the test and you will be 46 master mechanic😎. Great to hear.

Absolutely not a fact John - hahaha! But thanks for the kind words. The crazy back story on my suggestion dates back many moons ago (I was just a very young wrench turner in the Army) when I had the same brakes not releasing issue on an M60A1 tank. Same problem and same solution, but much harder to do inside the drivers compartment in the belly of the beast. Took me hours to figure it out.

Very glad your brakes are back in business!

That's a good question, Otto. I see many of these replacement MC for my truck and they have the side mounting points. After everything settles down from my test drives, maybe I should look at this for future replacements.

Contact these guys. Maybe they have one like your original or can rebuild yours if necessary.

Specializing in antique, vintage, classic, obsolete, unique and hard-to-find brake parts, bonding, riveting, rebuilding, drum and rotor machining, custom made brake hoses

Brake Materials & Parts Inc
800 Sherman Boulevard,
Fort Wayne, IN 46808
260-426-3331
http://www.brakematerialsandparts.webs.com/

A check of some of our usual vendors shows they are listing/offering the correct style 1/2 ton master cylinder that has the same mounting design as John's picture.

Classic Parts 1936-46 1/2 ton MC (Currently listed as arriving soon)

Jim Carter 1936-46 pickup MC (Currently listed as out of stock)

Chev's of the 40's 1938-46 1/2 ton MC (Currently appears to be in stock???)

The various vendors like several I found on ebay, partsgeek and others advertising master cylinders for John's application often seem to not use the correct picture for the application, showing pictures of the larger truck master cylinders which mount with bolts through the body sideways. Even Google AI results shows the wrong pictured style.

Best to thoroughly review the part description and applications list before buying to be sure you don't end up with the wrong part.

Since I was able to remedy the issue of a blocked by-pass hole in my master cylinder, I'm planning on using it unless I run into additional issues. I did see that Chev's of the 40's has an after market MC. Thanks for looking out for me guys!

Great it was the master cylinder for the fix, but the other problem could have been collapsed inner brake line even on brand new rubber hoses. Quality today. Btw I actually bought my master cylinder from rock auto for a lot less than the vintage resellers for my ‘37. I was shocked it was available. My original was extremely pitted and I found a place to sleeve it at a crazy price too.

I also bought a Dynamic friction MC from RockAutol and works like a charm. I am actually surprised. For $40 you can't beat it.