How to evaluate brake job

[Redleg130]

I recently got an M37. The brakes were squishy and I had to pump them so I read to bleed the brakes. I suspect what followed will reoccur with other systems (problems leading to other problems).

The bleeders were all frozen and some threads were rounded, so I decided to remove the cylinder to get force on the bleeders. I broke a steel brake line in this process, but got that replaced with a copper nickel one. One rear cylinder was leaking so I rebuilt it, and the front two cylinders were corroded so I honed and rebuilt those. The last cylinder I rebuilt to match the other three. I got them remounted and adjusted brakes per TM - move adjuster until it drags slightly. Replaced the bleeders and then finally was able to do the bleed task.

Now that it is done I test drove it and the brakes feel much better - no pumping and much more responsive, with much faster braking time. While that is good, I am not sure how to know if each cylinder is working correctly and if its behaving like an M37 should. Subjectively, it feels like the current brake power is safe but is there some sort of test I can do?

I cleaned each wheel (brake parts solvent spray) so I should see if there is leaking clearly.

Couple of other follow on questions:

What is the best way to prevent bleeders from freezing? Maint a couple times a year, grease on threads, some kind of anti seize?

The copper nickel lines seem really nice, very flexible and its stated they wont corrode. Is there any reason not to use these?

My front wheel hub is not stock, it has a dial for 2wd and 4wd. There is a grease fitting on the top next to the brake line hose. Who might make those so I can look up how much grease to put in there? I put some in, but didn't see a release valve, and didn't want to overdo it.

When I was enlisted I did operator maintenance, but never anything on this scale. I always send my car to a mechanic. This is interesting/fun, but I have no experience to draw on for this stuff so hopefully my questions do not seem silly. I don’t want to ruin this very nice truck.

[sturmtyger380]

If your brakes are working and all wheels are having the brakes work it sounds like you did the job right. These trucks were not super good at stopping unless everything is perfect.

Best way to prevent bleeders from freezing?

Good question. Time and sitting are what makes things on these trucks freeze up. I would suggest bleeding the brake system once a year enough to replace all the brake fluid. That helps keep moister out and you will free up the bleeder screw each time.

Front wheel hub is not stock, it has a dial for 2wd and 4wd.

Sounds like you have a selector hub that was added. That's a nice item to have. When in 2wd it keeps the front axle from turning all the time and helps increase your gas mileage.

Grease fitting on the top next to the brake line hose.

That sounds like the grease fitting that greases the top bearing of the knuckle. The fitting will grease that bearing but also will send grease down to the axle joint housing right underneath. If you use a hand pump to try and fill the housing it seems like you are pumping for days! I just wonder how much grease is left in that knuckle. I cleaned one out once. There is a lot in there.

How about some photos of your truck. We love photos.

[greeno]

There is a plug on the axle side of the knuckle that you’re supposed to remove, pump grease in the zerk until it comes out of the hole. I pack two tubes of grease in while rebuilding and then pumped another half tube in before grease came out that hole. So much grease!

[sturmtyger380]

Plug on the axle side of the knuckle that you’re supposed to remove

Yep, that's where I was doing all the pumping of the hand pump not the top. Forgot already, durn!

[NAM VET]

Perhaps more important than actual great stopping power, is that your truck does not pull strongly to one side or the other. Suggest you find a safe place and brake hard to see what will happen when you have to stop abruptly. One way to see which wheel may not be braking as well is to brake on a loose surface, and see if all four tires do the same. And when bleeding the brakes, be sure to close the vent line from the master cylinder, or you will just pump brake fluid out the vent, and not to the wheels. I always tend to forget this little necessary trick.

Have fun,,,, Drove my truck yesterday to a friends house, and in an hour or so will drive over to shoot at a nearby indoor range with a shooting buddy. NV

[Redleg130]

your truck does not pull strongly to one side or the other. Suggest you find a safe place and brake hard to see what will happen when you have to stop abruptly. One way to see which wheel may not be braking as well is to brake on a loose surface, and see if all four tires do the same. And when bleeding the brakes, be sure to close the vent line from the master cylinder, or you will just pump brake fluid out the vent, and not to the wheels. I always tend to forget this little necessary trick.

In my test drive I did do this and did not notice a pull in any direction, so it appears I am on the right track. I do not think my brake master cylinder is stock, it has two reservoirs which from my reading indicates a dual circuit setup, which is actually nice to have I think. I will look for a vent but didn't see one in looking, it has a metal cap with a snap clip, nothing like the pictures of stock masters.

I followed the TM "minor adjustment" procedure, but I evaluated the spacing mentioned in the TM -20 "Major adjustment" and found the shoes are not equal spacing, bottom adjuster is a few mm out. The anchor bolts are not just anchors, they are oblong and adjust as well, so Ill do that whole process. I may do a pictorial procedure for this since I had to reread the TM several times before the light bulb went off as to what is happening with these brakes (eg with the 4 oblong adjusters). My tool library is growing quite fast.

An answer to one of my original questions (how do I know the cylinders are working) may be that if they move freely, like if i compress them and they travel back, then they aren't stuck, which is what I am worried mainly about. I think it lurching to one side on a hard brake would be an indicator for stuck cylinder as well, yes?

For pictures:

In the field:

IMGP7668s.jpg (195.96 KiB) Viewed 1060 times

Working on the brakes:

IMG_20210929_170802s.jpg (239.51 KiB) Viewed 1060 times

I got this M37 since it seemed a lot more fun than a quad bike or SxS rec vehicle, and it is, I am having a blast with it. I will mostly do Amateur Radio "Parks on the air" with it, but it seems people like these in shows and such as well.

[NAM VET]

nice truck, and welcome. We lived in Topeka from '84 to '96, out on the west side of town. Next to Westridge mall, kids went to Washburn rural HS and Wannamaker Elementary. rarely back there now. Now in UpState SC. I just couldn't take the cold and the prairie wind. Hal, aka NAM VET

[Cal_Gary]

Great pix Redleg, definitely brings back some memories!
Thanks!
Gary

[Kaegi]

if its stopping well and you rebuilt all the cylinders they wont stick. the only time they stick is from sitting for years. If the shoes were a few MM out the pedal would be low. the space is around .010 in inches. 2 mm is about.050" the pedal would probably be low or spongy if that much clearance. Seems you probably good as is. always measure in inches. its more precise. ;/)

[just me]

If you are a bit more adventurous, you can do SOTA with an M37.

[PoW]

Yep, get a RT-68 with all the trimmings in that bed, the correct AB-243 antenna mount, and go to town on 6m FM.

Period correct and when tuned up, seems to work forever.

PoW