Brake question.

[Brady]

I have a stock '87 3/4 ton Suburban.I have been trying to fix my rear brakes.(locking up and not releasing)All new parts on the rear axle.Wheel cylinders,hardware and shoes.Also new master cylinder.Still doing the same thing.When I pump the brakes they lock up and won't release on their own.When I crack open a bleeder they release.

I figured I would start get the brakes locked and then crack open fittings working from rear to front.Trying to see when they will quite releasing.Got to that rear brake valve thing that is connected to the rear axle by a lever.When I crack open the OUT side it squirts fluid and the brakes release.When I crack open the IN it does nothing.SO I decided to pull it and see what was up.I pulled the spring and plunger.Both had some corrosion.SO I cleaned the hell out of it.Put it back together without the spring and plunger.Put it on the truck and the brakes seem to work fine now,but the dam adjuster thing leaks around the shaft the lever bolts to.

Anyone know the name of this thing and if you can get a rebuild kit for it?Can't seem find it in LMC or even in the Chilton's book I have.Thanks.

 

[Fordum]

Damnit, brain fart...... I can tell you what it does, and even come up with a name, but the correct term is lost in space right now.
The closest I can come right now, is its a Load Sensing Brake Proportioner.
The lever moves with the height of the frame above the axle, and controls how much fluid goes to the back brakes, and at what pressure, according to how much weight you have in the back. Plus, it also senses how much front end dive you have when braking hard and adjusts for that.
Some people swear by them, some swear at them. I know of some folks who have done away with them and say they have no problem. But I also know people who drive around with wire holding the tie rod ends together for a month or so until they can get around to replacing them.
I'm pretty sure the correct name has load sensing in it somewhere. Might do a search on that.
If it can be bypassed safely, I am sure someone here has done it and will chip in shortly.

J.

 

[Brady]

That name makes sense.I think you can bypass it just by pulling the plunger and spring.There is a bolt cup thing that unscrews from it.The spring and plunger are under this.This is what I was did.My problem is I messed up the shaft seal causing it to leak.I would actually like to have it working.I tow a 18 FT tandem with my CJ/buggy on it with the Sub.So having the brakes working a little more when needed is nice.

 

[Fordum]

If I have taken one of those apart, I don't remember. But you need to examine it carefully. It just sounds like the lever should not see any fluid under normal operation. But, like I said I don't ever remember pulling one apart.
I am sure they are available, just not sure where. I do remember a thread on another forum somewhere that discussed "tuning" one by adjusting the position of the lever via the mount point so as to make it more sensitive or not.

J.

 

[Brady]

You could be right.Maybe I will clean it out really good and put it back together and see what happens.I did try spinning the shaft to see if it would losen up and let the fluid flow.I turned it clockwise which would be like the rear getting lighter.It didn't make any difference.

 

[4X4HIGH]

The part in question is called a "load sensing proportioning valve" and they were notorious for being problemsome and most people remove it from the system.

 

[Brady]

Can't find any rebuild kits for this thing.So I am going to bypass it.Maybe tommorrow since I have a half day of work.

 

[Brady]

Bypassed the load senser thing.Brakes work and actually release now.