Rear brake not engaging

[wlkstout]

For inspection the other day I had to replace the all the brake hoses and rear pads for my new 92 Olds Cutlass supreme i just bought. I swapped the hoses and bled all the lines, adjusted the e-brakes but cannot get the passenger rear brake to grab upon driving conditions. And I know it was the one that was working previously because it was the pads that were worn down to metal. E-brake is holding.

 

Rebuild, replace or any other ideas? Thanks

[pitzel]

How are you testing it?  On mine, setting the e-brake when the car is in motion won't lock the wheels.  It will slow the vehicle by causing friction, but it won't actually lock the wheels.  However, it works as a parking brake, providing enough static friction to keep the vehicle in place. 

[Schurkey]

I had to replace the all the brake hoses and rear pads for my new 92 Olds Cutlass supreme i just bought. I swapped the hoses and bled all the lines, adjusted the e-brakes but cannot get the passenger rear brake to grab upon driving conditions. And I know it was the one that was working previously because it was the pads that were worn down to metal. E-brake is holding.

 

Rebuild, replace or any other ideas? Thanks

HOW did you retract the REAR caliper pistons to get the new pads in place? 

 

Did you BLOCK or REMOVE the brake hoses before pushing the rear caliper pistons back into the bores?

 

HOW did you "adjust" the "e-brakes".

 

 

 

 

 

Wild-ass Guess:  You need to set 'n' release the park brake about a hundred times.

[Imp558]

HOW did you retract the REAR caliper pistons to get the new pads in place?

 

 

Yeah that could be a factor but it seems like a hell of a lot of force would be required if one were to refuse to acknowledge that tool to turn the piston in properly.

I wonder if something rusty crusty fell in when the old line came off.

[wlkstout]

Have set the e-brake too many times to count. Have set the e-brake while rolling down the ally and it will grab and hold the tires, did lock them at the end but was on an early morning damp road. Used the loan a tool set from a-zone to turn the piston back in. And the testing is visual as it is showing no signs for wear on the rotor whereas the drivers side is showing wear and is putting off a hot brake smell occasionally.

[wlkstout]

I did not remove the hoses prior to doing the rear brakes. Probably should have but didn't think about it at the moment.

[95GS]

This may not be your trouble, but:

 

Last week a mechanic told me of one front grabbing caliper on his older GMC minivan  >> pulled to one side.

He changed both front calipers & fluid - didn't help.

 

Called his uncle, retired GM dealer mechanic.

The problem was corrosion within a brake line union,

I believe where the rubber hose meets the steel line w/ bracket.

 

Apparently one line was almost blocked, like an artery on the Standard American Diet.

Let me know if you need more details.

[Schurkey]

Yeah that could be a factor but it seems like a hell of a lot of force would be required if one were to refuse to acknowledge that tool to turn the piston in properly.

I wonder if something rusty crusty fell in when the old line came off.

Actually, I've NEVER "turned" the piston using the crappy "special tool".  I don't turn the pistons at all.  I remove one nut and one washer from the emergency brake lever, remove the lever, and then push the pistons STRAIGHT into the bores with a C-clamp Vice Grip.  The screw turns instead of the piston.  About a thousand times easier.

 

My concern about blocking or removing the brake hoses is that the most contaminated fluid in a brake hydraulic system is usually in the calipers, and when you push or turn the pistons into the caliper bores, all that contaminated fluid gets shoved backwards through the ABS valving.  This is NOT GOOD.  Therefore the hose should be disconnected or blocked, and the bleeder screw opened so that the fluid leaves the caliper via the screw and not the hose.

 

And I never did get an answer about how the E-brake was adjusted.

[wlkstout]

And if you read the original post you would have seen that I bled the system at all 4 points. And by doing it the entire system has fresh fluid so pushing the piston in albeit did push contaminated fluid back was subsequently all bled out.

 

As far as ebrake adjusted... how I read and did it on my 91 by repeatedly setting the brakes. Worked fine on the 91 both sides and the drivers side of the 92 but not the passenger.

[RobertISaar]

My concern about blocking or removing the brake hoses is that the most contaminated fluid in a brake hydraulic system is usually in the calipers, and when you push or turn the pistons into the caliper bores, all that contaminated fluid gets shoved backwards through the ABS valving.

 

do the pistons displace enough fluid to push fluid all the way up from the rear calipers to the ABS modulator? quick calculation assuming 3/16 brake line with an inner diameter of 2/16 is that the entire distance of line from the modulator to the caliper should be something like 1.8 cubic inches assuming a ~150" line run. with a 35mm piston, it would need to travel around 1.2" to fill the entire line's volume with fluid from the caliper. I've never measured rear piston travel, but the combined thickness of both pads is just over 29mm(1.14in), including the backing plates(about .2" each).

 

I don't know how much mixing occurs, but it seems like if the pads were run all the way down to their wear indicators, pushing the piston back in would only send the fluid about 2/3 of the way back towards the master cylinder. for the front calipers, i can easily see it happen though, those line runs are just too short for it to not happen.

[Schurkey]

And if you read the original post you would have seen that I bled the system at all 4 points. And by doing it the entire system has fresh fluid so pushing the piston in albeit did push contaminated fluid back was subsequently all bled out.

 

As far as ebrake adjusted... how I read and did it on my 91 by repeatedly setting the brakes. Worked fine on the 91 both sides and the drivers side of the 92 but not the passenger.

1.   IF the ABS gets contaminated fluid, the valves may stick and no amount of bleeding could fix it.  Maybe yes...maybe no.

2.  Repeatedly setting the e-brake?  You didn't adjust the e-brake.  You adjusted the rear caliper piston.  The e-brake adjustment is done to the cable, using a nut and threaded section, under the chassis, below the driver's door somewhere.

 

do the pistons displace enough fluid to push fluid all the way up from the rear calipers to the ABS modulator? quick calculation assuming 3/16 brake line with an inner diameter of 2/16 is that the entire distance of line from the modulator to the caliper should be something like 1.8 cubic inches assuming a ~150" line run. with a 35mm piston, it would need to travel around 1.2" to fill the entire line's volume with fluid from the caliper. I've never measured rear piston travel, but the combined thickness of both pads is just over 29mm(1.14in), including the backing plates(about .2" each).

 

I don't know how much mixing occurs, but it seems like if the pads were run all the way down to their wear indicators, pushing the piston back in would only send the fluid about 2/3 of the way back towards the master cylinder. for the front calipers, i can easily see it happen though, those line runs are just too short for it to not happen.

That would be good news.

[White93z34]

I'd say chances are the sliders are siezed solid in the calipers. I don't know why that happens so much on those early calipers, You'll likely need to either pound them out, clean and re-grease or replace calipers.

[Dreaded Mechanic]

The calipers and hoses are known to get corroded and blocked.