FJ Rear Brakes Sticking...way worse when hot... (1 Viewer)

[71GFER]

I have a nightmare going here, working on my buddies 71 restored FJ, so we have no idea of what parts it has...
It ran great last year, but after storage the rear brakes are sticking and just about every other fluid is leaking, it basically went to crap mechanically.

It has a 4 disc conversion
I see a new master cylinder, and new lines
Both rears a dragging hard when hot (a little when cold), when you park it you can hear them release after a couple minutes
Rear discs are 100 degrees hotter than front, so I'm sure its only the rear.
As I said before, this did not happen last year, it only presented after storage...(that should rule out a few issues, rod length, heat etc...) On short trips it seems fine.

Any help would be appreciated...

 

[peesalot]

Replace the rear calipers, you can take a look at the existing ones, when they release like you described its a sign they may be able to be saved but I find the cost of new calipers vs. the time it takes to rebuild/refurbish a win and Oriellys has a lifetime warranty so after you get the first set they are free.

 

[71GFER]

Replace the rear calipers, you can take a look at the existing ones, when they release like you described its a sign they may be able to be saved but I find the cost of new calipers vs. the time it takes to rebuild/refurbish a win and Oriellys has a lifetime warranty so after you get the first set they are free.

I have no problem doing that, it an easy fix, I just didn't think both would go bad at the same time so I didnt consider it.
The car is cool now and they move freely.
There is a splitter back there, while everything else looks pretty new, it looks very old, do they ever clog up in one direction?

 

[Tancruiser]

I had the same issue ended up being the rubber lines

 

[71GFER]

I had the same issue ended up being the rubber lines

Someone installed stainless braided lines in the rear, I don't like how tight some are flexed, but I'm hoping that isn't the issue. I just shortened the rod a little bit for now, I think its a longshot, but its all I can do on a Sunday night. Plus it's easy...

Oddly enough, the brakes never seem to stick for me, I'll have the owner stop over and drive it in the next couple days.

 

[4x4veteran]

I had the same issue ended up being the rubber lines

There should be one rubber line in the rear connecting the metal line from master cylinder to the metal lines running across the rear axle to the right and left brake calipers.
That rubber line is probably collapsing on the inside and not letting the brake fluid pressure release thus holding pressure on the brake calipers.
I have seen rubber lines that look new on the outside but are deteriorating on the inside.
Work the brakes until they get warmed up and sticking then release pressure via the bleeder valve.
If it frees up the brakes then dollars to doughnuts it is the rubber hose.

 

[Downey]

I suspect rear brake pressure that is not bleeding off once the rear brakes are released, pressure staying at the pads, pads rubbing constantly while you are driving. If this is the case, then after a long drive, while you are parked at a red light the pads can literally melt themselves onto the rotors, then the vehicle will not move at all. Been there, done that. Possibly residual valve or proportioning valve are working as a one-way valve, not pissing off pressure once you release the brake pedal ???

 

[71GFER]

There should be one rubber line in the rear connecting the metal line from master cylinder to the metal lines running across the rear axle to the right and left brake calipers.
That rubber line is probably collapsing on the inside and not letting the brake fluid pressure release thus holding pressure on the brake calipers.
I have seen rubber lines that look new on the outside but are deteriorating on the inside.
Work the brakes until they get warmed up and sticking then release pressure via the bleeder valve.
If it frees up the brakes then dollars to doughnuts it is the rubber hose.

They are definitely all braided...

 

[4x4veteran]

I suspect rear brake pressure that is not bleeding off once the rear brakes are released, pressure staying at the pads, pads rubbing constantly while you are driving. If this is the case, then after a long drive, while you are parked at a red light the pads can literally melt themselves onto the rotors, then the vehicle will not move at all. Been there, done that. Possibly residual valve or proportioning valve are working as a one-way valve, not pissing off pressure once you release the brake pedal ???

Ok, so the metal lines have been replaced with braided rubber, all the more room for collapsed lines.
Might check the proportioning valve as Downey mentioned but my money is still on the rubber lines.

 

[pbgbottle]

Next time they lock up crack the bleeders and see what happens. FLuid may spurt out. I don’t think those stainless lines have rubber inside just saying. Those caliper are slightly different that what I’m used to seeing usually the brake lines have a banjo fitting on the ends also.

 

[71GFER]

I cant figure out why someone would do a complete restoration, including brake lines, and keep the old hoses. I will change all three, since it should be done anyway. I'll report back, in a few days...

 

[71GFER]

Also, should I go back to rubber, or stick to braided? Recommendations on where to get them?

 

[pbgbottle]

I would think the stainless lines are fine for now. I would think the calipers may be cooked now and the pistons are not sliding in and out freely maybe
Or what master cylinder did he use if it is a stock 1971. It may still have the residual valve in the master used for the rear drum brakes. Or if used the mini truck or 80 series master it may not be adjusted properly at the brake booster rod. That’s where I would look.

 

[71GFER]

Here is the master cylinder, I have no clue where its from... This entire FJ is a mystery...

 

[peesalot]

If they were power washed or even the little sprayers at the car wash and the calipers were directly sprayed then I would bet that the calipers are sticking. May have been just a thin line of crust that has broken free. Could also be the residual valve in the MC, have you checked to see if thats gone ?

 

[bikersmurf]

I'd go for a drive, get them to lock up and see if loosening the master cylinder bolts 1/2 a turn will get the rear cylinders to release. If the push rod is too long, it'll cause the brakes to lockup. Typically it'll lock all four... however something else could be at play.

 

[peesalot]

change the calipers and be done, they are done, sticking randomly, happens , had it happen on 3 calipers, every time after I washed the truck and sprayed the calipers off, truck sat, brakes stuck, would unstick sometimes, tried compressing piston, cleaning and what not, never really got a sticky one going again to my satisfaction, just swap em out.

 

[71GFER]

Trying to piece these parts together sucks. Is there a kit that includes hoses, t, calipers, rotors, and pads? I'll just do everything and be done with it.

 

[71GFER]

Ok, so the metal lines have been replaced with braided rubber, all the more room for collapsed lines.
Might check the proportioning valve as Downey mentioned but my money is still on the rubber lines.

Can you guide me to where I can find hoses like the picture I posted above?
There are about
1 foot - right disk
2 feet - left disk
1.5 feet hard line to t-fitting

I replaced the calipers and they still stick.
When I crack the bleeder, fluid squirts out. The lines are new, so I believe you were correct about the hoses. But I can't find them anywhere...

 

[Tools R Us]

... When I crack the bleeder, fluid squirts out. ...

Was that master intended for rear drum brakes, looks like it? If so there is likely a residual valve under the fitting for the rear brake line. On a drum setup, the residual valve holds slight pressure to prevent them from fully retracting. When converted to disk, if it's not removed, will cause them to drag. It's just a little spring and like rubber stopper thing, that works kinda like a one way valve. In most cases can be removed or replace the master with one intended for four wheel disk.