I have a 88 with 193000 and replaced the front pads last week (they were pretty rough) in any event, I am now unable to go more that 5 or 10 miles and the wheels heat up real bad, cant even move the wheel when I jack it off the ground and try to spin it. i have taken the calipers off 3 times, greased the slides put them back together but no help, still heat up, the pads dont back off. Any suggestions ??
Thanks in advance, Dino

 

........all the wheels or just select ones?...kinda sounds like the calipers are locking up or frozen....when was the last time you flushed and bled them?

 

Possible adjustment of actuator rod from booster need correctly adjusted. If booster or master was changed, this could be the cause.

Agree with the flush idea, but calipers might need new seals, and walls of cylinder cleaned up to be free.

When you pushed the pistons back into cylinder, did they slide easy?

Did you crack the bleeder when you pushed the piston in?

And as said, what wheels?

 

.........i don't think he changed out the master but, only the pads so actuator length may not be an issue if he didn't have the problem prior....

....as for seals, unknown as he didn't make reference to any leaking fluid.....

......as for cracking the bleeder, i have heard many stories that pushing the piston back w/o opening the bleeder could damage the abs pump. however, not having first hand knowledge of this, me myself - i always crack open the bleeder and expel the extra fluid at that point in th esystem.....

 

keiko: Some questions for you!

1. Are all four wheels getting hot and locking up or is it just one or two wheels. More info on this please.
2. When you replaced the brake pads, did you do anything to the master cylinder?
3. Did you flush out the ole crappy black brake fluid and replace with fresh fluid?
4. Did you use any petroleum cleaners on the brakes when you changed out the pads.

I assume you did not have this problem before you did the brake work. It sounds like the pistons in the calipers are frozen and will not withdraw when the brake pedal is released.

Something you did during the brake repair has caused this problem!

My comments!

 

Well I figured I would replace the old calipers as new ones were not that much, well the problem is still there. It is only on the front wheels. One thing that may help get me an answer is when I jacked up the car (the wheels were hot and frozen tight) and opened the bleeder it freed up the wheels. the master is only a year old and i didnt have this problem prior to replacing the pads. Any Ideas
Thanks Dino

 

check the hoses.They perish and can break down internally and pressure is able to activate the brakes but it is not released keeping the brakes on.I learned this the hard way with my old Rolls-$4500 hard ways!!

 

The simplest explanation is usually the right one. If it was me, I'd pull 1 caliper off at a time and remove the pads. Place a block of wood in the caliper where the pads were (to keep the piston from fully extending), then have someone lightly apply some pressure to the brake pedal. Watch the piston and see if it travels out smoothly.

Then try lightly pushing the piston back in by hand or slowly with a C-clamp. If it won't go back in, you can try taking the cap off the master reservoir and resting it on top (maybe even put a clean towel over it to avoid splashes). Try to slowly push the piston back in again. Don't force it quickly or you'll shoot brake fluid out the reservoir like a geiser.

If still no go with the new calipers, you may have a stuck proportioning valve or dirt in the brake line that is maintaining pressure to the front brakes.

 

So now he has new calipers so forget about rebuilding them. Having two bad front flex lines, unlikely. So prove my initial theory wrong.

Jack up the car, check to see if the wheels are frozen and then unbolt the master. Just remove the nuts to loosen so it can move forward about an inch. (But do not completely remove from car). Now check the wheels, if they are free, the actuator rod needs adjustment. If wheels still frozen, you have eliminated one simple item and you can move on.

The ABS pump can cause a restriction to fluid flow if defective and has happened many times. However 2 wheels. That’s hard for me to believe also but just one more thing to keep in mind.

One more thing. Possibly when the new pads were installed and the pistons were pushed in, I suppose its possible the prop valve in the master could have moved and got stuck and just wont reset to its normal position. However if you cracked the bleeder as you pushed the pistons in, then forget this.

 

WellI figure the stuck proportioning valve is probably my best bet, after all when I pushed the fluid back into the resivour at the initial repair it hadnt been done in 10 years, is there any way to check this beside replacing it ?
Thanks Dino

 

There probably is with some work.

Remove the master from the car and remove the big bolt on the end of the master. To get out the valve, tap the end of master on a piece of wood till the valve starts coming out. Once it comes, then you can pull it. Be careful of the springs, washers and spacers that come out. Keep them in order and don’t loose anything. Then you can clean up the bore and valve. The actual valve has some internal working parts, spring and such. I’m not saying take it apart (unless something looks wrong, a vice and “C” clamp remover are recommended) at this point, but give it a good visual.

Clean out master best as possible using clean fluid, reassemble and bench bleed. Put back on car and try again.

Give it a shot, hopefully it will work out.

 

If you try this first remove the plastic sensor that screws into the side of the proportioning valve body.

 

jack up the fronts so you can rotate the wheels.
1. start the car, and leave it in neutral/park
2. apply the brakes with the engine running
3. check to see if the wheels release
4. if they don't release, crack the brake line at the master cyl for the fronts.
5. if there's pressure there, the problem is in the master cyl.
6. if the wheels don't move, and there's no pressure at the master cyl, the problem is the hoses, lines, calipers, etc.
7. if you release the pressure at the master, and the wheels free up,
tighten up the brake line again, and reapply the brakes.
if the wheels don't free up,
8. loosen the two bolts on the master cyl. to relieve the pressure that the booster is exerting on the master cyl. If the wheels free up, the booster needs to be adjusted.
9. If it still doesn't free up, the master cyl. should be replaced.

the master cyl is basically an aluminum housing with an aluminum piston with steel springs. the springs may rust and deposit crud in the path of the piston, and the crud can act as an abrasive, and erode the bore, and the surface of the piston or cause the piston to bind. If it indeed looks like the master cyl is no good, replace it as the liability of a rear end accident would break you if a lawyer got a hold of the fact that you were compromising his client with mickey-moused parts that were either defective or non-functioning.

 

Ok let me get this right, I jacked up the car backed off on the bleeder (wheels were frozen) Fluid squirted out and the wheel freed up. is this the master or booster that is giving me trouble ? Also the master is only one year old (rebuilt from Auto Zone)

 

The booster pushrod can cause this. It's possible that prior to this you had air in the system, which gave the fluid room to expand without dragging the front brakes. When you pushed the caliper pistons back in to install the new pads, you forced this air out of the system (excellent way to bleed the system btw). Now when the fluid heats up, it causes the pads to apply. If this is the case, you need to remove the master (keep lines intact) and make sure the booster rod is shorter than the depth to the master piston. Anytime a master cylinder or booster is replaced this measurement should be checked.


It's also possible that you dislodged the proportioning valve somehow during bleeding. This can happen if you're bleeding one circuit while the other is already bled, as it will have pressure only on one side of it, but it should reset after the system is bled. This problem would also cause the brake warning light to go on.

 

buy new brake hoses. 200,000 miles is a tell tale sign.

 

So you think the hoses suddenly decided to fail both at once during the pad install? I don't think so.

 

but with that much mileage (heating and cooling cycles) and that old, it's not a bad idea. but that's not the problem.
your problem is that the fluid isn't returning to the master cylinder reservoir.
The usual stumbling block to that event, is the master cylinder.
if the booster isn't holding the master cylinder partially actuated, it's the master cylinder.
If you got it at auto-zone, you should have a warranty. take it off, and take it back. get a new one, and it should fix it.

 

I'd check the booster pushrod and prop valve first, these cost $zero to do, and are the mostly likely culprits, IMO.

 

Well I suppose I will try a new master, I am not well versed enough to fgure out the travel from the booster rod or what to do if it was to long (I would assume that the rod is hardened steel) I appreciate everyones help and will let all know what the cure was. This board is extremly helpful. Plan on getting to it the first of the week

Thanks Dino