Rear Drum Brakes

[Ayres]

While bleeding the brakes I found that the left rear brake would not bleed any fluid out of the bleeder valve. I removed the bleeder valve and pumped the brakes and no fluid came out the hole where the bleeder valve was installed. I also removed the inlet line from the back axle two way valve from the brake and fluid came out of the line. Sooooo my guess is the valve is messed up. The questions I have are:

1) Does my analysis sound about right? Piston assembly is messed up somehow?

2) How hard is this to fix? I read through the shop manual I have and it seems like a lot of springs and settings. Would it be worth my time? I am an average mechanic I would say.

3) If I were to take it in to have this problem fixed and the brake bleeding performed what am I looking at for cost?

Thank you for any help you can provide.




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www.inficad.com/~sungodra/fsj/FSJ.html (http://www.inficad.com/~sungodra/fsj/FSJ.html)

[jimzamx]

I think if you have enough corrosion to hold fluid you should just replace the wheel cylinder. They're cheap and easy to replace. Most auto parts shops have them in stock. Just be careful removing the pipe to the wheel cylinder.

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'90 GW all stock
'86 GW w/lift (laid over)
'69 AMX 390 4spd

[andy d]

trine to get oriented here. rear brakeline runs between proportioning valve and rear end, then to a hose which allows for rearend suspension.on the left side is a tee that runs the brake line to the wheels. thats just a tee isnt it? if the hose leading to this passes fluid,but the tee doesnt, i think your problem is forward of the tee. remove the tee. clean out whatever is blocking it,is it rust or rubber? the tee acted as a choke point to catch the disintegrating lines up stream. your rig is 22yrs old. up here in the rust belt, a 78 is on its 3rd set of steel brake lines and prolly the rubber ones are about due. you are prolly looking at redoing the rear lines. might as well do the wheel cylinders at the same time. its not really a bad job


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'88 gwag,pure stock

[UnkleMunky]

Ditto on the Wheel Cylinder suggestion!

If you're getting flow at the axle location, then your next main spot(and last flow spot) is the wheel cylinder. You can get rebuild kits, but frankly, I'd just say buy a whole new cylinder and go with that(not much more and you get a whole unit in new condition).

Your current one can be faulty and even "rebuilding" it might not fix it. Replacing it is cheap, fairly simple, and will take care of any cylinder problems. If you can disconnect the line AT the cylinder, and apply pressure, and see if you're getting fluid THERE, then the cylinder is the problem. If NOT, then check THAT chunk of line. But, still, it wouldn't hurt to replace cylinder(s).

Usually cylinders aren't THAT bad, but here's a fun story: The WORST cylinders I've ever replaced were on my '77 J10 a few years back. Brake line just between the axle junction box and one of the wheels had rusted through and broke......and it looked like it was amazing it hadn't rusted through earlier(like YEARS earlier)!

"Ideally" I would have only had to replace that little chunk of line and bleed the brakes, but noooooo......

Bolts were rusted to the cylinders, busted them off or stripped them(I forget), so had to replace cylinders....BOTH sides. Cylinder bolts were rusted.....umm.....like rust-welded to the housing...NO budging them! Had to take the dremel cutter and cut right through the cylinders to get them loose and out. Those cylinders are cast iron if I recall, and I went through a bunch of cutting disks on that job! Shoes needed replacing too, so what the heck, did a whole brake job while I was at it! http://www.ifsja.org/ubb/smile.gifActually ended up fairly cheap....like under $50 for ALL the brake parts if I recall. A couple days of work on it, due to the fun, and liberal amounts of FSJ-induced cussing!

If I'd taken it somewhere to be looked at, I would have been laughed out of the shop and told to just have a junkyard haul the truck away...it would have cost a LOT to have that brake job done! I drove the truck another 2 years without any brake trouble!

Do what you have to....it CAN be done! Just follow the directions for replacing and you should be fine.

A BIG advantage to new wheel cylinders is how much better bleeding goes....night and day difference on some I've worked on! You might even want to just do a whole brake job if you can afford it.

(PS...bleeding works a LOT better with two people...one on the brakes, and one at each wheel...just in case you haven't done that before!)

Enjoy!

Michael
'78 J10/'76 J10

[Ayres]

The leak is deffinately in the cylinder in the wheel. The tee at the rear azle definately has fluid coming out of it and the wheel cylinder is stopped up with something. From what I am hearing it sounds like a good thing would be to do the back brakes while I am there. I did not look too much at the shoes but I assume they are warn. I am also assuming that if the left side cylinder is broke the right one is not far behind. What parts should I ask for at the parts store? two sets of brake shoes and two cylinders?

[okidoc]

I just bought rebuild kits for the rear cylinders. There are two sizes of rear brake. If you have the ten" drums(or so) you have the 7/8 wheel cylinder. If you have the 11" drums you're wheel cylinders are 15/16. The wheel cylinder kits are $4-5 each and parts monkey carries rebuilt units @ $10 a piece. Rebuilds are easy if you have any questions just e-mail me.

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Dude, where's my rig?

Why do my cars break down when my wife drives them?