M37 Brake Question

[Jimma]

We have been working on our 1963 M-37 and doing brake work. Having almost no driving time on the vehicle prior to brake work I am not sure how hard the brake peddle should be. We have been bleeding and re bleeding the brakes. Can anyone tell me just what to expect as to peddle firmness?

 

[m376x6]

The brakes when adjusted properly are pretty hard and little pedal down travel. But there's the catch. Getting these old brake shoes to adjust properly is really tough. There are the bottom adjusters which place the bottom of the shoes close to the drum but also raise and lower the shoe to get even exposure to the drum top and bottom. Often times since a lot of these old drums are worn there isn't a lot left of adustment to get the shoes right next to the drum. Too much gap and you'll end up pumping the brakes each time to get the pedal to firm up at the top when applying them. There are small clips on the drums that you can loosen and get a good look at the shoe/drum gap as you adjust them. A feeler gauge works best. Often since the drum is a bit worn turning them only makes matters worse. So you will often get a slightly out of round drum which will rub at spots. If you suspect you have air in the lines I can offer a solution I found works for me. The filler opening at the top of the master is a standard pipe thread. I went the local big box hardware store and bought some fittings to work on the master cylinder then bushed it up to a 6 inch 1 1/2 inch diameter pipe. I brought it back down at the top to thread a air quick disconnect fitting. I attach the contraption, fill the pipe up and connect my air hose to it with between 10 and 20 psi. I can now connect a hose to each wheel cylinder as I power bleed each. Really helps to fill the lines and get rid of air. Don't let the master run out of fluid or you'll be doing it all over again. If you're interested I can probably post a pic of that neat little inexpensive power brake bleeder. Good Luck.

 

[Jimma]

Thanks for the advice and help. If you can post a picture that would be great.

 

[glcaines]

I drove several M37s while in the Army and one owned by a friend. The only thing I remember about the brakes was that they all had a very hard pedal. Are you planning on bringing it to the GA Rally?

 

[Capt.Marion]

The brake system will also bleed itself out over time through usage and, strangely enough, through sitting. I know two people whose M37s' brakes have stiffened up after sitting for a week or so-- Squirt-Truck and 1958M274.

EDIT: I assume that your truck is not currently driving. I would highly wait until it is driveable before spending too much more time adjusting and bleeding the brakes. Once you get it driving you can test drive it and see how the brakes actually function--i.e. you have to pump the brakes to get it to stop, or it'll lock all four wheels up if you even look at the brake pedal.

 

[Mac53]

The breaks should practically be like stepping on the floorboard.... Very firm

 

[Jimma]

We bought the truck and its at a friends who is working on it. We have not driven it but to the shop to address some electrical issues and he tracked down the problems. It needed a new generator and voltage regulator. Also, needed a fuel pump and the correct fan belt and new spark plugs. Got those taken care of so its running fine. We knew it needed some new brake cyliners and we replaced those. He has been bleeding the brakes but said the peddle is still a little soft. Its drivable now but just need advice on the brakes.

 

[repairs_nooooo!!!]

A few years back my dad had an M-37. One of the main things I remember was that after every time we changed the brake fluid, I would have to sit in the truck and manualy pump the brakes for 30+ minutes. After draining the fluid, all of the pressure is lost and you have to build that pressure back up again.

 

[Jimma]

Thanks for the info.

 

[m376x6]

I'm doing a break job right now as a matter of fact. Adjustin the brake shoes to get as reasonably close as possible before I power bleed them. I really don't worry too much as long as after the truck will stop. The idea is that after I have driven it several miles stopping it at short intervals, I'm seating the shoes and drums together. Then I can go back and get a real close adjustment that I couldn't before.

I'm back late tonight, I'll post a picture of that power bleeder in the morning.

Another thing to mention. If not properly adjusted the front shoe on one or all of the wheels will grab when you apply the brakes and lock it up until the truck comes to a complete stop and rolls back ever so slightly to free it up from the drum. A real attention getter when all of a sudden after just touchin the brakes one or more tires are skidding.

 

[Charlie 6]

My M37 brake pedal is hard as a rock when depressing. Brakes stop the vehicle.

 

[m376x6]

Here's a pic of the power bleeder I made up. It has a small hand valve at the bottom to help with not losing the brake fluid when removing the bleeder from the master cylinder. Hopefully the pic will be seeable.

 

[m376x6]

I'll try a 100k pic. It's a little bigger when you click on this one. I left the top large bushing hand tight to fill the bleeder once it's attached to the master cylinder.

 

[Capt.Marion]

You can also use a garden pump sprayer and use some hose, a brass ball valve, and some brass fittings to connect the hose from the output side of the sprayer to either the junction block on the top of the master cylinder or straight into the master cylinder.

We made one for our M37 and made another one for the M35A2, and they both are incredibly handy.

 

[ranger.41]

jimma,
I used a pressure bleeder to bleed the brakes on my m-37. Also make sure that the vent to the air intake is closed when using a pressure bleeder. As m-376x6 said, on each wheel there is an inspection clip, or a slit in the drum, insert a .006 feeler guage in to the slit and adjust each corner of the breakshoe. I started with the lowwer adjustment first then the upper. Before I adjusted the brakes on my truck The pedal would go 3/4 of the way to the floor then on the second pump they were rirgt on top. The proper adjustment made all the difference in the pedal movement.
ranger.41

 

[m376x6]

jimma,
Also make sure that the vent to the air intake is closed when using a pressure bleeder. ranger.41

I forgot to mention the vent, Good catch, Thanks Ranger

 

[Torisco]

Thanks for the valuable info.

 

[seemach1]

Hello,

I recently purchased a new to me 1963 M37, i am changing all the fluids and I changed the brake fluid. I hooked up my mighty vac and I bleed each wheel in the proper order, keeping the master cylinder full. There is absolutley no pressure in the pedal, if i keep pumping it builds up, but once i stop fluid omes out of the vent in the master cylinder and I loose all pressure.

Any ideas?

Thanks,

Chris

 

[mattveeder]

Sounds like you need a new master cylinder. They were made at a time when things were not as exact as modern master clinders.

 

[seemach1]

Well i bought a new master cylinder, this one had the hole where the vent is blocked off. Having the same issue, i also adjusted the shoes in all 4 corners.

I am at a loss, any ideas?