Right brake grabs & locks

[firefox]

Not sure if it is front or rear though. It is intermitant and usually at low speed under 5mph.
Does this sound like a brake bleeding or wheel cylinders. How do I test?
Thanks for any help,
Bruce M1008

 

[AceHigh]

I think grabs and locks means some fluid leaked out of the wheel cylinder on to the linings. Best to pull both front and back and inspect.

 

[LanceRobson]

Bruce, when it grabs does it feel like the truck is being held back or more like a giant has a hold of the rear bumper? Sometimes you can feel one or the other. The pull from behind feeling would indicate a rear brake.

You could try to replicate the action on a gravel surface with someone observing from outside. The reduced traction would tend to aggravate the fault and make it easier to find.

When you brake lightly at 20 or so MPH, do you feel any pulsing in the steering wheel or the brake pedal? It could be very slight. Either a rotor with a hard spot that varies in thickness or a drum with a hard spot that wore into an oval may cause low speed grabbing.

If you feel it in the wheel its likely an out of flat or warped rotor.

If you feel it in the pedal it could be that or that a drum with a hard spot wore into an oval and lets the shoes grab the high spot. The best way to isolate that fault is to lightly set the parking brake at about 20 MPH so that it barely makes contact. If the drum is out of round you will feel the truck cogging from the intermittent friction. Since the parking brake only actuates the rear brakes that will settle the front/rear question.

If it's a front brake it could be a sticky piston. A sticky wheel cylinder may drag some but wont usually grab. This will be felt more as you release the brake pressure.

It could an internally swollen flexible brake line. The liner of the line can sometimes swell. That lets the high pressure through but won't let it drop back down quickly. Sometimes this can cause a delay in one brake working and allow it's opposite number to grab but usualy you would tend to feel this as more of a drag when releasing the brake than as a grab when applying it.

It could also be contaminated brake pads or shoes. If brake fluid gets on them they can get very "grabby", especially the rears. If the "grab" is sudden and out of proportion to the amount of brake pedal force I'd check this first.

Occasionally a brake will stay on from a bad hydroboost that does not fully return to rest but that would usually show up in the brake closest to the master cylinder-in this case the left front -and would also show up after you release the pedal, not when you step on it.

To sum up-I think an out of flat/round issue or contaminated pads/shoes are the places to start looking.

Good Luck

Lance

 

[notsosanestan]

i would jack up the right side of the truck and have someone press the brake pedal

 

[grayw0lf]

As mentioned earlier, I'd check & replace the flexible line if it looks old. You can't tell from outside, but they do often clog / collapse when old. If you do that, you might as well replace the wheel cylinder at the same time & take both pieces out of the puzzle.

 

[firefox]

Thanks alot folks!!!
Bruce

 

[chevy79k5]

i got the same thing going on in the back of my m1009. except mine locks up as soon as you hit the brake even the litelest bit. i know that it is the back passenger side just havenot had time to look at it yet.

 

[M813rc]

Something else to check- the pins that hold the caliper on.

When I picked it up, my 'pretty' M1009 dived for the right ditch on brake application (alarming, and enough to immediately deadline the truck pending repair). Turns out the drivers side front caliper is only held on by one of the required two pins (the other pin is MIA) so it rotates up off the disc when you hit the brakes.

Cheers

 

[burbn10]

My M1008 was having all sorts of crazy brake issues and it ended up being mixed brake fluid. The previous owner added DOT3 to the DOT5 system. After I drained it all out and bled the lines clean the brakes have been working great! DOT3 and DOT5 mix like oil and water. Or actually more like silicone and alcohol.....

 

[fstfrdy]

flush the system u have air in lines had the same problemm getting locking up one of the rears had to do full flush to get it right

 

[skark_burmer]

So does mine, you guys actually fix them?
I just turn left as im stopping. The harder the stop, the more left i turn!

 

[firefox]

Thanks fstfrdy. My wife stopped asking. We have one now.
Bruce

 

[ca1517]

Have a 1009 that does the same thing. My problem is actually a leaking axle seal. Oh what fun.

 

[rosco]

Look at the inside bottom of the backing plates. If its been leaking long, you will see fluid. It will make the brake sticky. But also, It can be from broken or missing parts inside. There is the TM, on how to do things, but that doesn't have anything to do with how things are actually done. You should locate the problem as soon as possible and repair it.

Lee in Alaska

 

[justinwregier]

Brakes pulling can be a seized drum but a leaking axle seal could also be a bad wheel bearing. A bad wheel bearing with a leaking axle seal and pulling to that side while braking can lead to wear on the differential gears and axles.

Are the hubs hot to the touch after driving? If so then I would have a look at the differential just to be safe when repairing the drum or caliper.

Pulling brakes in the front may be a seized piston in the caliper. I have seen a rotor that looked like it could be a topographical map of the sea floor from continued braking on a seized caliper, yet my sisters suburban kept on driving?! Like a ROCK

Anyway have a wheel off on each point of concern and check the brakes. A drum shoe and a caliper brake pad both show wear about the same but any other issue will stand out. The axle seal will hang out if its bad and differential fluid will be present if the axle moves noticeably out of center. A bad wheel bearing will typically have the ball bearings trickling out of the axle shaft, if they are still in there
In any case pulling brakes are not safe to drive with since brake failure can be terribly unpredictable and dangerous. U joints can breakup with driveshafts, axles and wheels can disagree on which direction to rotate, or the truck will just dive right if your lucky or worst swerve left... All of which I drove through once just to skip towing to still afford home repairs. Not smart and now that I know the warning signs I would rather walk with my thumb out

Time to take off a wheel FUN! or just get a whole new axle assembly