Rear Brakes Locking Up

[bookit]

Let’s think simple for a minute check the “E” brake / parking brake to make sure they are fully releasing the lever should release nearly to the rear shoe it only takes a little bit of tension on that cable to make a rear wheel lock up also make sure the rear brake shoes are the correct size and installed correctly

 

[Knuck55]

Was not going to sift 8 pages but Make SURE the master cyl has been bench bled correctly. Seen that problem more than once. Sorry if this has been mentioned already.

 

[59840Surfer]

Never push a brake pedal to the floor.

If the master is contaminated - it can pack crap in the forward piston seal and ruin it.

Always assume the master is contaminated and put a 2x4 or 4x4 under the pedal to keep your "helper" from jamming it all the way down.

Good help is hard to find and bad help makes you buy a lot of extra parts.

In all my years as a Brake/Lamp/Smog Inspector for the state of California, I have never seen GM use cross-fed brakes; that is if one fails the other two will take up the load, diagonally.

Dual masters have always had a front-rear split in that once the proportioning valve shuttles to the leaking side, the brakes that are applied are the survivors ---> front or rear.

Yes --- there were systems that shut off any flow to the ruptured system (front or rear) because the reservoir only had a small dam to keep the front and rear fluid kinda-sortta-almost segregated.

Has anyone told the OP to physically inspect the rear brakes for 90wt or brake fluid contamination or reversed primary/secondary shoes?

Brakes that grab or chatter or make noise, do it for a simple reason --- stop looking for zebras when you hear hoofbeats. Dem's only horses!

 

[Ricko1966]

Never push a brake pedal to the floor.

If the master is contaminated - it can pack crap in the forward piston seal and ruin it.

Always assume the master is contaminated and put a 2x4 or 4x4 under the pedal to keep your "helper" from jamming it all the way down.

Good help is hard to find and bad help makes you buy a lot of extra parts.

In all my years as a Brake/Lamp/Smog Inspector for the state of California, I have never seen GM use cross-fed brakes; that is if one fails the other two will take up the load, diagonally.

Dual masters have always had a front-rear split in that once the proportioning valve shuttles to the leaking side, the brakes that are applied are the survivors ---> front or rear.

Yes --- there were systems that shut off any flow to the ruptured system (front or rear) because the reservoir only had a small dam to keep the front and rear fluid kinda-sortta-almost segregated.

Has anyone told the OP to physically inspect the rear brakes for 90wt or brake fluid contamination or reversed primary/secondary shoes?

Brakes that grab or chatter or make noise, do it for a simple reason --- stop looking for zebras when you hear hoofbeats. Dem's only horses!

O.P. had his brake lines reversed at the master. So bias was totally wrong.

 

[idahovette]

I thought some of the old Citations had the cross split systems

 

[59840Surfer]

I thought some of the old Citations had the cross split systems

I know I inspected a bunch of them and to tell you the truth --- I do not remember seeing cross-fed brakes on any domestic vehicle.

Some Euroboxes did it --- Citroens, Vauxhauls, Opels, a few Fiats and maybe the Gordinis --- but I do not remember any domestic cars doing that.

If I'm wrong ---> I can learn.

 

[Goldie Driver]

If you are still not sure if you have the front and rear in the right spot, trace them from the MC to the Portioning Valve. If they are correct, I’d say change the PV.

OK - I believe this picture is correct. Now, I would have ASSUMED the rears get a smaller line versus the fronts. That is not the way my 1980 half ton is plumbed and you can not reverse the fittings on the master cylinder- different sizes. I tried and found out.

So - is my stuff mis-plumbed from the General? Assuming the rear chamber is the rear brakes - both appear to be the same displacement.
Color me lost.

 

[Moodyalaskan]

I was always taught in front disc and drum rear vehicles large reservoir is for front brakes as they require more fluid in the caliper to function properly.

 

[Broken85]

OK - I believe this picture is correct. Now, I would have ASSUMED the rears get a smaller line versus the fronts. That is not the way my 1980 half ton is plumbed and you can not reverse the fittings on the master cylinder- different sizes. I tried and found out.

So - is my stuff mis-plumbed from the General? Assuming the rear chamber is the rear brakes - both appear to be the same displacement.
Color me lost.

@Goldie Driver; when you have eliminated all the possible, what remains no matter how improbable, must be the truth. So if you traced them from the PV back to the MC, then what you found has to be the truth. I can’t really tell from your pictures how they trace back, but those lines don’t look factory and that master cylinder looks like it belongs on a B17, so; is that the correct master cylinder? Did the PO mangle those lines into place to make them work on the wrong MC?? Hard to tell without more info.

 

[Goldie Driver]

@Goldie Driver; when you have eliminated all the possible, what remains no matter how improbable, must be the truth. So if you traced them from the PV back to the MC, then what you found has to be the truth. I can’t really tell from your pictures how they trace back, but those lines don’t look factory and that master cylinder looks like it belongs on a B17, so; is that the correct master cylinder? Did the PO mangle those lines into place to make them work on the wrong MC?? Hard to tell without more info.

Actually, I was doing a little research on my work computer earlier today so can't link it but found a video of a 78 with the same set up and a you tube video showing that the forward ports on older cars often power the rear brakes.

So , I believe it is factory. Doesn't explain why my issue is the opposite of the POs but it is what it is !

 

[AuroraGirl]

Actually, I was doing a little research on my work computer earlier today so can't link it but found a video of a 78 with the same set up and a you tube video showing that the forward ports on older cars often power the rear brakes.

So , I believe it is factory. Doesn't explain why my issue is the opposite of the POs but it is what it is !

You must be registered for see images attach

This is for a van, but i cant find your master in the lists in the service manual
Should be obvious looking in the master which is the front and rear, front uses more space. if your fluid isnt clear you can stick your finger in the nasty to feel the iron casting for which one is bigger

 

[Goldie Driver]

You must be registered for see images attach

This is for a van, but i cant find your master in the lists in the service manual
Should be obvious looking in the master which is the front and rear, front uses more space. if your fluid isnt clear you can stick your finger in the nasty to feel the iron casting for which one is bigger

Well, here is my old one I saved in a plastic bag in the garage. So much for protection from the Houston humidity...



However, it does show the front chamber is smaller. The front is to the right.

I never knew.

 

[AuroraGirl]

Well, here is my old one I saved in a plastic bag in the garage. So much for protection from the Houston humidity...



However, it does show the front chamber is smaller. The front is to the right.

I never knew.

So I guess just make sure the combination valve, the front circuit is hooked to the rear chamber

 

[Goldie Driver]

So I guess just make sure the combination valve, the front circuit is hooked to the rear chamber

Yup.

Large line up front and connected to the right of the spool valve switch.