Rear brake woes

[Subaru_dude]

So, my right rear caliper started intermittently sticking back in June. Replaced it, same problem on left rear. Replaced it, and it's been pretty normal. I had noticed that the rears get warm while the fronts will be nice and cool after a drive. But hey whatever, it's getting good mileage and isn't becoming a problem on my 100 mile 70mph 1 way commute.

 

But last night, the right rear started sticking again. So I removed the caliper to press the piston in which didn't seem stuck at all, and then greased the pin because it didn't seem to be sliding all that easily. Didn't fix it so stayed the night at a friends house and pulled the hose and caliper this morning. Parts store said the hose looked fine and I could blow air either direction through the hose. So, I am a little stumped because, wouldn't a sticking proportioning valve cause both rears to stick equally? Thanks for any input at all. Would love to fix it soon, otherwise I'm stuck driving a 96 Camry to work.

[Subaru_dude]

Completely forgot, 1994 Legacy wagon 4eat awd.

[Bushwick]

Are the pins straight? What grease did you use originally? I forget which car it was I used to own, but it too had the same issue and no amount of grease fixed it longer than a couple weeks. 

 

 

If it were me, I'd replace the pins/slides (my 95's left rear needs looking at, and haven't torn Subaru brakes down yet so I'm assuming they have 2 slide pins?) and spray some degreaser into the holes where ever they set into the caliper. You might have scale rust in there and you might have a slightly bent pin. Be sure to spray the rotor down after and have the pads removed to avoid getting grease/dirt on them. Brake parts cleaner works best. Also, spend a few bucks and get a quality slide lube. Shouldn't be using axle grease.

 

As far as heat goes, that could either be normal or from a dragging caliper. If the rotors are NOT vented in the middle, or have low air flow vs. vented fronts with more air flow, they can get warmer in the rear.

Edited October 11, 2015 by Bushwick

[Fairtax4me]

Did you try to spin the wheel and compare it to the other side?

 

Was the caliper clamped tight on the rotor when trying to remove it?

 

After removing the caliper, can you freely spin the rotor?

Edited October 12, 2015 by Fairtax4me

[Subaru_dude]

It didn't want to spin with the caliper on and was resistant to being removed but once removed I could press the piston in with a wrench, reinstall and put the wheel back on which spun freely before being let down, go for a drive and jack it up again just to have it not spinning freely with . So yes the rotor spins freely without caliper but also with freshly squeezed caliper.

 

Bushwick the calipers came with the part the caliper bolts to with pre-greased pins. Definitely seem to slide side to side smoothly. Didn't think about the rotors being solid, good point.

[Bushwick]

One down side to certain styles of calipers is they drag a little. Might be more pronounced with fresh pads, but after a quick break-in, you should be able to put the car in neutral and have the wheels spin freely off the ground. A slight dragging can be considered normal so long as the caliper isn't binding. 

 

As long as the wear pattern from the pads is one solid contact patch (on both sides of the rotor) and there are no grooves, loud grinding, squeals, etc. and the calipers aren't seized, I'm usually content. When you see reduced wear patches with rust built up where it should be clear metal, OR you can smell the hideous odor of burning pads, that's when it's time to get worried about them. If you can smell brake pad material in the car at stops with windows down, that's normally a dragging caliper.

[Subaru_dude]

When you see reduced wear patches with rust built up where it should be clear metal, OR you can smell the hideous odor of burning pads, that's when it's time to get worried about them. If you can smell brake pad material in the car at stops with windows down, that's normally a dragging caliper.

Yep. These are the reasons for the post in the first place.

[Loyale 2.7 Turbo]

I kindly suggest to check the Brake fluid Lines, because the Flexible Rubber Lines and also the Metallic Lines could become Partially obstructed, due to several reasons; the most common reason for partial obstruction on flexible rubber lines, is old brittle rubber disintegrating from the inside.

 

A piece of dirt could make the lines to work as a Check Valve; and the Metallic lines might have a small Bent, on a curve... 

 

Kind Regards.

[idosubaru]

A collapsed internal rubber brake hose can cause fluid to not be able to move and the piston can't retract.

 

But - this is more common on american and other cars, i've never heard of seen of it in a Subaru.  if this was a Ford Escape, I'd say replace the hose.  But being a Subaru I'm hesitant.

 

Here's how you test these:

1. step on brake - get brakes to "stick".

2. loosen bleeder screw to let pressure off

3. note they are now unstuck

4. press brakes a few times while turning wheel and BAM it sticks again.

5. release pressure again.

the brake hose is collapsing internally and not releasing.

 

Besides repeating the steps - you essentially did that exact test.  Maybe the hose is collapsing only at certain times or only under load?

Edited October 12, 2015 by grossgary

[1 Lucky Texan]

do the pads move freely in the caliper? some folks have had to file/grind pad backplate tabs/ears smaller. Or maybe rust in that area could cause binding?