All new brakes and a cooked rotor

[zayd]

Well I just finished up my LX's front axle service, including switching birfields. I also threw new rotors, 100-series pads and caliper rebuilds into the mix since I needed to service the brakes anyway. Everything went together fine aside from a broken knuckle stud I'll need to replace. Bled the brakes also.

After I put the calipers on and spun the hub by hand, I noticed the passenger side was slightly tighter than the driver side. I didn't think much of it as I expected the 100-series pads to be a tight fit on the new rotors. I took it out for a quick test drive, came back, and the passenger side rotor was smoking hot -- to the point that it actually blued the outboard surface. The inboard surface was fine but saw just a narrow streak of pad contact.

I pulled that caliper and disassembled it again. I made sure all fluid ports and passages were clear, polished up the piston walls, and checked the bores for any problems. Nothing to report there, so I'm stumped.

I'll put the caliper back on tomorrow and test it out. But what else could cause this issue? If these were sliding calipers and the slides seized, I could understand how only one side of the rotor was engaged. But these are rigid calipers and all four pistons moved smoothly in their bores. Some archive reading suggested it could be a brake line issue, but I don't understand that.

I plan to put a dial indicator on the rotor to see if it warped. Assuming it is within OEM specs, could the heat ruin a rotor in other ways?

Thanks folks.

 

[Parsnip]

<snip>what else could cause this issue? <snip>

I've seen similar failure modes caused by a flex brake line failing internally and acting like a one way valve and another time a tiny little spring in an ABS pump failed and it too acted like a one way valve.

I suggest you attempt to push the pistons out on the caliper with a very gentle push on the pedal to get them to move a bit and then see if you can push them back in. Suppose you had your old pads and assuming they are thin compared to the new ones. If you put them back on that should let you push out the cylinders safely and see if you can get them to return with a disk brake expander tool or the handle of a hammer as shown in the FSM.

If you can't get the pistons to go back in then suspect something in the line or ABS.

 

[Howard705]

New pad or rotor slightly thicker than it should be? Especially outside pat that side. Causing interference on the outside pad. Tightening caliper bolts slightly shifting/cocking it in to get tight. Loosen caliper bolts slighty-try turning wheels. Try pushing pads back one at a time with screwdriver with wheel off. Try other wheel same way.

 

[TAOTAOMOTNA]

Similar situation

Same thing happened to my 85' suburban, it was the brake line. Just today the front passenger is getting hot and you could smell the brakes. I bled it last week because there was a little dirt. I'm going to bleed it tommorrow and hope it , helps cause I wanted to get new lines w/lift kit let's hope for the better. Happy holidays from Guam.

 

[jonheld]

It sounds like you need to remove the anti-squeal shims until the pads wear down a bit. You said it was a tight fit upon reassembly, which it shouldn't be. You can also remove some pad material to give clearance.
On the other hand, you could try using the correct parts for your vehicle, as opposed to trying to shoehorn in pads that were meant for different calipers, but that's just me.
All the other theories presented would not explain wear on only 1 side of the rotor/pad interface, as the fluid pressure is equal to all 4 pistons.

 

[94SRUNNER]

Did you put shims in with the 100 Series pads? If so they should be removed and only pads installed.

 

[zayd]

No shims, just the pads -- I didn't even try given the recommendations here. I'll get the caliper back on and give it another go. If the problem persists, I'll likely try a new brake line first.

 

[Funner]

The problem is that the pads were dragging on the rotor and the dragging overheated it. Many people have had to remove material from the pad to make them fit without dragging as you described. Some just need to remove the shims, others need to remove a little brake material in addition to the shims. I had this problem on my 80 after replacing the front pads with 100 pads. I caught it quickly enough to not roast my rotor.

 

[zayd]

Interesting. I was under the impression that the 100-series pads were the same thickness as 80 pads, only taller. Isn't that the case? If not, then it makes much more sense to go back to 80 pads.

 

[zona]

My understanding is the 100 series brakes will not provide any additional performance--rather they may last a little longer. Since this is most likely not your DD I'd humbly suggest you go back to the 80 pads.

I'm not a brake expert, but, I am an four star armchair general.

Zona

 

[NLXTACY]

Interesting. I was under the impression that the 100-series pads were the same thickness as 80 pads, only taller. Isn't that the case? If not, then it makes much more sense to go back to 80 pads.

The 100 series are both taller and thicker.

 

[86tuning]

Interesting. I was under the impression that the 100-series pads were the same thickness as 80 pads, only taller. Isn't that the case? If not, then it makes much more sense to go back to 80 pads.

The 100 series pads are both thicker and wider, putting more friction material onto the pad, and therefore giving longer service life. There is no noticeable improvement in braking performance, just brake service life.

They're about 1mm thicker, so the pad shims need to be removed for ~5-10k miles until they wear down a bit and the shims will fit back in.

Since you already own the 100 pads I would just fix the sticky issues and put it all back in, unless the pads are so cooked that they're no longer serviceable.

 

[gray rider]

Hey 86
Have you actually put the shims back in after some wear?
I'm running the 100 series pads also...

 

[86tuning]

Hey 86
Have you actually put the shims back in after some wear?
I'm running the 100 series pads also...

Still waiting for my pads to wear down enough. It's been a year and they're still full thickness lol. I'm using porterfield street pads in 100-series fitment, and they wear like iron.

 

[zayd]

The 100 series pads are both thicker and wider, putting more friction material onto the pad, and therefore giving longer service life. There is no noticeable improvement in braking performance, just brake service life. They're about 1mm thicker, so the pad shims need to be removed for ~5-10k miles until they wear down a bit and the shims will fit back in. Since you already own the 100 pads I would just fix the sticky issues and put it all back in, unless the pads are so cooked that they're no longer serviceable.

I see -- thanks. In that case, I may go back to 80 pads. I'm not looking for improved braking, but the extended life was attractive.

I put the caliper back in again and the passenger brakes seem to be better. No overheating rotor but an occasional grind that sounds like a stuck piston. I'm going to cut my losses on this rebuilt caliper and replace it with a reman unit. The driver side is doing fine, but I'll probably replace it as well to maintain braking symmetry. I'm really stumped on this one as both calipers were in great shape when I tore them down -- clean, smooth pistons and smooth cylinder bores.

I'll report back!

 

[86tuning]

Inspecting for bad hoses is simple, just spin the rotor a few times to see if its sticky. If not, pump the brakes a couple times and re-check. If its sticky now, open the bleed valve and watch for a spurt of fluid, indicating residual pressure. Repeat and compare to the other side.

Residual pressure is usually caused by one of two things:

1) improperly adjusted brake master pushrod. This usually affects both sides.
2) blocked brake hose

You can also tear down the suspect caliper again to inspect, there would be no harm in doing so. If its sticky again, then go with a genuine reman caliper even though you spend a bit more its worth it.

 

[IdahoDoug]

80 factory brake pads and 150 posts a year about this issue would disappear from Mud.....

 

[zayd]

Inspecting for bad hoses is simple, just spin the rotor a few times to see if its sticky. If not, pump the brakes a couple times and re-check. If its sticky now, open the bleed valve and watch for a spurt of fluid, indicating residual pressure. Repeat and compare to the other side.

Residual pressure is usually caused by one of two things:

1) improperly adjusted brake master pushrod. This usually affects both sides.
2) blocked brake hose

You can also tear down the suspect caliper again to inspect, there would be no harm in doing so. If its sticky again, then go with a genuine reman caliper even though you spend a bit more its worth it.

Brian -- thank you. I'll check the hoses per your test. As for the caliper, it's been disassembled twice now and checks out, so I can't imagine that it's the problem. If I check/replace the hoses and move to replacing the caliper next, who sells genuine remans? I've put my eyes on remans from NAPA and Advance and they look like different castings.