(Yet Another) Brake Thread

[dbesade]

So,

last summer I was driving along in my M35A2 and my airpack locked up, causing me to drag my brakes for around 5 miles until I had a place to pull over. I drained the tanks and the brakes released... called a buddy and we slowly got the truck home. I decided it would be a good time to rebuild the brake system with new lines, wheel cylinders, rebuild the airpack (duh), and repack the bearings. I had shoulder surgery in December so just now getting around to doing the finishing touches like getting wheels on and bleeding brakes. Got all that done today.

Result... a super hard and high brake pedal with pretty decent braking power. I hear a "whoosh" when I step on the pedal and nothing appears to be dragging (I got up to 15MPH and hit neutral to see if brakes were dragging). A few drums are hot but I suspect they need further adjustment. Any suggestions from those who have done this before?

Regards,

Dave

 

[texas30cal]

Did you clean/rebuild or replace the master cylinder? Drums may be warm due to adjustment being too tight or due to brakes not releasing completely. Jack it up and apply/release brakes and see if they drag. If you turn the adjusters top and bottom to increase the clearance (drum to shoe) and they still drag then you have a problem, if this releases them then readjust to spec. I’ve had issues with frozen adjusters, patience, oil, and hammer required, you may have to remove the drum and shoes in order to get adjusters out then polish/anti seize them. You can’t just set the bottom, set the top , and be done, one affects the other so I always go back and forth a couple times per wheel. After the first one it gets easier. My brake pedal as well as two others I’ve worked on gets firm approx 3/4-1” above the go pedal. Results may vary, some assembly required.

 

[gimpyrobb]

I would lean toward the brake pads being too close to the drum. I've found .015 gap top and bottom to work really well.

 

[dbesade]

I would lean toward the brake pads being too close to the drum. I've found .015 gap top and bottom to work really well.

You are probably spot on... when I got this truck it had amazing brakes so in all the years I've never really had to adjust them. I did try the TM method but I may readjust using the .015 method.

I did not touch the master cylinder since it had no issues... I'm gunna check it tomorrow when I do some more brake adjustments. Any tricks to adjusting with wheels on ?

-Regards,

David

 

[dbesade]

I would lean toward the brake pads being too close to the drum. I've found .015 gap top and bottom to work really well.

Nailed it. Adjusted the front brakes and found the passenger side was all wacked... took it apart and re-adjusted.. pedal is normal now. Thanks for the assist!

 

[gimpyrobb]

Sorry I missed your earlier reply.

I usually jack up an axle then use the hole in the brake drum to instert the feeler gauge. If you don't jack up the whole axle, you won't be able to spin the wheel.

Glad you found the issue.

 

[oboyjohn]

When I was still in the service, I would jack up one wheel at a time and remove the drive flange ( or drive axle for the rears). Then I would adjust the pads so that when I gave the wheel a good spin, it would make approximately one complete rotation after I let it go. I would then road test it and verify that all the drums were at or around the same temperature. This method always worked for me.

 

[gimpyrobb]

That works best for me too, but if you don't want to replace the axle gasket and get gear oil all over, just jack up the whole axle and you can get by.