97 Astro rear brake issue

[astro fan]

Replaced worn drums, shoes & springs and cylinders last fall. Flushed fluid and bled whole system. The right rear wheel has been locking up ever since at low speeds in city driving causing the ABS to kick-in sometimes.

When gently applying parking brake at low speed, something seems out of round as the deceleration is sort of on & off, you know like when you have out of round drums or disks. Replaced drums 3 times, replace right axle as I thought it was bent slightly and the problem won't go away.

The van might be pulling slightly to the right when brakes get hot which may indicate the right side works better?. It is possible that one of the new cylinder is defective or that someone screwed up somewhere and that they'd have different piston diameters.

Please someone steer me in the right direction before I go completely insain!!

[old_master]

Drums would be the obvious thing to check first, but you mentioned that you have replaced them 3 times, I assume that means both sides. If that's the case, you can pretty much rule out drums. The big clue here is that it acts up with the parking brake. That eliminates the entire hydraulic system and the front brakes as being the cause. You replaced one axle, check the other one. Excessive lateral runout of the axle hub, (bent) can also cause a pulsation in brakes. If both axles and wheel bearings are ok, and the axle seals are not leaking fluid onto the shoes, the only thing left is the shoes themselves. Possibly an out of round condition with the lining, or some other abnormality with the shoes.

[astro fan]

Thanks Old Master - I will swap lining between sides and if the problem moves with the parts I'll know it's the lining.

[old_master]

Make sure you have the shoes on correctly. The shoe with the short lining, (primary) goes toward the front of the vehicle.

[astro fan]

Old Master,
I compared the shoes from side to side and no obvious differences. I put them in the drums and they fit nicely.

I did find a broken spring on the right side, you know, the little one that keep the shoe against the back plate and the wheel is not locking up anymore.

I still have the issue when the parking brake is applied. I tried checking the axles with the wheels off the ground and the right side may be off a little, but it's hard to tell for sure. I'm gonna have to visit a friend of mine that works in a workshop and we'll put a dial indicator on the end of the shaft.

Anyways thanks for your help again and I hope this might help others.

[old_master]

Did you notice a difference in lining length when you compared all 4 shoes? There should be two with shorter linings than the other two. They are to be installed toward the front of the vehicle. Did you swap the shoes from one side of the vehicle to the other and try it? If one or more linings are not arched correctly, you wouldn't see it with the naked eye and it still could cause locking. Years ago we used to have to arc the shoes to the exact diameter of the drum before installing the shoes. EPA said it was too dangerous breathing the dust and outlawed the procedure.