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RIGHT REAR BRAKE LOCKS UP


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dave691971
New User

Nov 9, 2008, 9:20 AM

Post #1 of 3 (5315 views)
RIGHT REAR BRAKE LOCKS UP Sign In

YES THE CYLINDER WAS LEAKING. THE INSIDE OF DRUM WAS FILLED WITH GREASE AND BRAKE DUST. REMOVED ALL SPRINGS AND OTHER HARDWARE AND CLEANED THEM BEFORE REPLACING EVERY THING. THE PARKING BRAKE WORKS FINE. THE SHOE FACING THE REAR OF TRUCK IS THICKER THAN THE FRONT ONE BY[ ] THAT MUCH. IT IS VISIBLE ON THE TOP 3 INCHES OF REAR SHOE WHERE IT IS GRABBING THE DRUM WHEN I APLLY THE BRAKES. THANKS FOR YOUR HELP.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Nov 9, 2008, 10:51 AM

Post #2 of 3 (5302 views)
Re: RIGHT REAR BRAKE LOCKS UP Sign In

Somehow you have this thread in two spot but no problem.

The "wet" shoes from brake fluid might clean up - only a maybe. Oil soaked ones don't and either will have erratic friction from too much to too little. Even wet drum brakes do that - if you ever owned a vehicle with drum brakes on the front you had to get used to wet weather driving and purposely DRAG them the heat them up to dry.

Brake fluid is water soluable and will also look clean with "BrakeKleen" but they really aren't IMO. You know almost nothing used drum on fronts anymore so it's rare to even know how those felt.

If cables and adjustment are in spec and one back brake is selectively grabbing more than the other I'll blame the lining. What you might notice is when it's hot - like purposely drag it with parking brake in a safe area without overdoing it, it may improve or change such that other side grabs more.

The solution is to get rid of those shoes and really is best to machine the drums as new shoes will break in better with machined or new drums and new wheel cylinder to other side as well. If you didn't change out the return springs - just do it. They probably don't cost $10 bucks for all of them!

There's another lurking possibility - the other side may have ONE frozen (probably front) piston in its wheel cylinder such that more psi of force is applied to the now fully working one. Some trucks will design rear brakes to work harder than fronts by the "proportioning" valve to accomodate expected loads.

Note: You don't really notice imbalance of force of rear brakes like you do fronts.

Again - If grease seals are leaking that oil won't clean off and you'll be right back there doing the shoes again so bite the bullet and do those if evidence of gear oil is there.

Remember - brake fluid will wash off with plain water and the grease won't so you can tell which is which if a total mess.

IMO - gotta go back and finish the job,

T



Loren Champlain Sr
Veteran / Moderator
Loren Champlain Sr profile image

Nov 9, 2008, 11:09 AM

Post #3 of 3 (5300 views)
Re: RIGHT REAR BRAKE LOCKS UP Sign In

Dave; Yes, usually when a brake locks up prematurely, it is because of contamination (brake fluid, gear oil). The 'longer' of the two shoes is the secondary shoe which is towards the rear of the vehicle. The primary shoe (shorter one) goes to the front. The secondary does most of the braking. The primary is a trailing shoe. If only the upper portion of the shoe is showing wear, I would presume that the brake is waaaaay out of adjustment. If your vehicle has a slot (at the bottom) of the backing plate, you can adjust the brake through that slot. This can be a bit tricky if you (and probably do) have self-adjusting brakes. Take a good look at how the self adjuster operates while you have the drum off.You will notice that by putting a small flat blade screwdriver through the slot, you can push the adjuster lever away from the star wheel. You'll need to do this while you are adjusting with the drum in place. Put the drum, wheel/tire assy. back on. A rule of thumb; Hit the brake pedal a few times to position the shoes; Using a brake spoon or another flat blade screwdriver, Adjust the star wheel to the point that you can't turn the tire/wheel by hand. While pushing the adjuster lever away from the star wheel, back off the star wheel to the point that the tire/wheel is 'just' free.
If your vehicle doesn't have the slot in the backing plate, you're screwed. No, just kiddingSmile. Adjust the star wheel manually a little bit at a time, putting the drum on and turning after each adjustment. Continue doing this until the drum is contacting the shoes while you turn it. Then, with the drum in place, hit the brake pedal a couple of times, recheck your adjustment. Whew. I hope you can understand what I wrote. :)
Use denatured alchohol (or Brake Clean) to clean the drum and backing plate and any greasy fingerprints. You can use fine emery cloth to clean the shoes. Remember, cleanliness is next to Godliness. Btw, you mentioned grease. If it was, actually, grease (and not brake fluid) then, you have an axle seal leaking and will have to replace it or the same thing will happen to your nice, new, brakes. Good luck.
Loren
SW Washington






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