I have one hot brake drum

[kiotiugly]

On my new-to-me M35, it seems as though I have one rear brake shoe sticking (maybe).

The symptoms consist of one brake drum that is about 400 degrees, while the other 3 rear drums are all about 70 to 90 degrees. There's also a smell of something burning (brake shoe material might be my guess).

I've looked at the TMs, although not as thoroughly as I will in the next few days. I thought that I might get some advice from you guys that have worked on your brakes before. Any idea what might be the most likely culprit as to why the brakes aren't releasing? I'm not familiar with an air/hydraulic braking system (I've only had the truck 4 days so far). I am fairly familiar with regular drum brakes, and the diagrams for the TM look pretty similar.

Also, is there any trick to getting the drum off? I know on some of my old trucks you can manually pull the shoes in and (sometimes) the drum comes off fairly easily.

Thanks in advance for the help. Take care.

 

[Recovry4x4]

Read your TMs for more details. Chances are better than average that you do have dragging shoes. Causes are mal-adjustment, broken return spring or broken hold down springs. Rarely will a wheel cylinder cause this. Don't fear the air/hydraulic system. All the air pack does is boost your brakes and meter air to the rear for trailer brakes, everything else is a basic hydraulic system. On the backing plate there are what appears to be 2 11/16 bolts at about 10 o'clock and 2 o'clock. These are minor adjustment points and the ones at the bottom with a big locking nut are for major brake adjustments. If you can't remove the the drum, you can rotate both of these adjustment bolts towards 12 o'clock to adjust them back and relieve pressure. I seriously doubt that your problem is hydraulic as it's only effecting one wheel but after a drive if you want to crack the wheel cylinder to see, you can do that. Just be forewarned that the BFS will be scalding hot and will burn you in a nano-second. Now, go to work.

 

[Lex_Ordo]

I just recently found the same problem with mine.

It is my right rear, rear.

There are those adjustment screws, and small cover plates that are on the backing plate.

Jack the wheel up, remove the covers on the backing plate. Now rotate the wheel and see if it sticks anyplace. loosen the top adjustment screws on the 10 and 2 position and see if the wheel turns more freely.
(Remember, turning towards the center tightens the shoe against the hub. turning away from center loosens it.)

There is a feeler gage number of I believe .020 that needs to be between the shoe and the drum.

This should correct the condition. If your axle was hot then I would also recomend the bearing re-pack, but if it was just your drum, you probably are ok.

 

[gringeltaube]

........................................
...........................................................There are those adjustment screws, and small cover plates that are on the backing plate.
..................................................

Cover plates on the backing plate?????

(Remember, turning towards the center tightens the shoe against the hub. turning away from center loosens it.)

??????????????????????????

 

[maxim]

Per haps you should consider having a new brake cylinder, and axle seals on hand before taking it all apart. If the hub/drum got that hot the seals may be toast. If the removal shows only the brake shoes stuck, fine, but if the cylinder will not retract it should be replaced and no better time than when you have it all apart. The TM's are most helpfull and walk you through the procedure of seal, cylinder replacement, and brake adjustment.

 

[rosco]

Usually, but not always, the problem is with mal adjustment, or broken return springs. Check the adjustment first. That is easyest. Those vehicles, while in service, don't always get the level of service described in the TM's!

Lee in Alaska

 

[gringeltaube]

Usually, but not always, the problem is with mal adjustment, or broken return springs. Check the adjustment first. That is easyest. Those vehicles, while in service, don't always get the level of service described in the TM's!

Lee in Alaska

, especially on the last sentence!

 

[kiotiugly]

Here's and update, with some comments and other questions:

First of all, this is my first vehicle larger than a one ton. So I jacked the truck up, took off the lug nuts, then removed the outer wheel. Then I tried to take off the inner wheel (like on my old one-ton dually). I pulled and pulled, I pried with bar, with a long piece of wood, got to the point of getting a chain and come-a-long hooked to my tractor, and then I thought .... I need some advice.

So I called the fellow that I bought it from and explained that the inner wheel must be frozen/galded on the hub. There was some discussion, and then he said the magic words.

"You DID take the inner lug nuts off, right?"

More silence on my part.

In the end, that did the trick. By the way, there was hysterical laughter on his end of the line after my silence.

Anyway, after that, I go the axle/hub/etc. dissassembled and the drum was stuck on. So I adjusted the bolts as indicated in this thread. After I got the drum off, it was pretty obvious that the shoes where dragging at the top. For what it's worth, the shoes, cylinders, springs, etc. looked practically new (I had noticed that the bleeder on the inner sides was shiny when I bought it). It makes me wonder if the truck has possibly had a brake job prior to a term or storage and just was never adjusted properly.

So me and the boy took it for a test drive and after a few miles up and down the road with a lot of intermittent braking, we got back home and I checked the temperature. Both of the drums ont he back axle were about 120 to 130 degrees. The front-rear axle (middle axle, whatever) drums, however, were only about 70 to 80 degrees. So here's my next question:

Should all of the drums be about the same temperature? I'm wondering if it's possible that the middle axle shoes might be out of adjustment (to the "loose" side). Again, I've been reading through the manuals and they don't indicate that you shoudl get more or less braking from one axle than the other, so I'm guessing I need to check all of my adjustments.

Thanks for the help, fellas. It turned out to be not as bad as I had feared.

And I haven't gotten it to overheat again, so maybe everything is okay.