Rear Rotors Show no Sign of Use?

[CaptainXL]

Interesting dilemma going on with my brakes that has left me scratching my head.

About a year ago I put some Wagner thermo quiet pads all around with new hardware and new rotors. I also flushed the brake fluid all around.

From day one the front pads made a horrible squealing like a city bus stopping and didn't brake worth a damn unless I was getting off the highway. So I chalked it up to these thermo quiets not braking well when relatively cool. Yet the problem continued even after a few months of use. So after much debate and realization that I must have gotten bum pads I replaced the fronts with Wearever ceramics and the noise is gone, problem solved. Now braking is much improved but still feels somewhat heavy to stop this beast.

Fast forward one year later and I think there is still a problem with the rears. After close inspection it appears the rear rotors have no groove marks or any marks whatsoever to indicate the rear brakes are wearing normally. the other day I felt back there and it was toasty warm so the rebuilt calipers must be clamping.

So I ask myself are the pads taking the abuse and not the rotor? or is my master cylinder not proportioning enough fluid to go to the rear? Does anyone have any tips on where to start looking?

The vehicle still seems heavy to stop and my suspicions are that the thermo quiet pads I left on the rear are not working at all to bite into the rotor. Maybe change those pads as well like I did the fronts?

Also curious would a pad ever just glide over a rotor and never bite into it? In my 20 years of working on cars I have never experienced this. Perhaps I bedded them in wrong?

 

[Old Coot]

If it were mine, I would want to have front and rear brake pads with the same coefficient of friction, i.e. from the same manufacturer and type material.

Double check the hydraulic system for air in the line. It is very easy to introduce air into your brake lines. With a dual section master cylinder if one section is air free and the other is not, it may be difficult to tell by the feel of the brake pedal if there might be air in the brake lines. It might not feel mushy or soft. Be sure to have the Mrs. or a friend help with the process. Be certain to hold the brake pedal to the floor when tighening the spigot! Also, be sure to keep checking the master cylinder for fluid during the bleeding process. Do not allow it to get low and introduce air into the system. Since you are looking at the hydraulic system this is a great time to inspect metal brake lines for corrosion and flexible lines for cracks and replace as needed.

Just because the caliper is rebuilt doesn't always mean it works properly.

I would check to be certain the caliper is functioning properly. Pull the wheels and set up a dial indicator to check for pad movement on both the inner and outer pads. Bear in mind this movement will be quite small, perhaps only a few thousandths of an inch.

Make sure the pistons are not cocked in the caliper. If they are, piston movement may not happen, with pressure applied they may just get wedged into a locked position and do no braking at all.

Many vehicle these days have floating calipers, meaning they are allowed to move back and forth. Be certain this function is working properly and that the mating surfaces have the proper lube if required.

I hope this helps ...keep us posted on what you find.

 

[dockers]

If you don't see signs of use after a year something's not working properly. Agree with above, same pad manufacturer and material is a best practice.

 

[CaptainXL]

Thanks for the help guys. I will get the new pads/ scuff up the rotor a bit and see where that takes me.

I also remembered that I replaced the rear axle seals at that time. Perhaps they failed again and there is oil back there and that's part of the problem.

Will keep the forum updated.

 

[Sparky]

If the seals were bad I'd think it would be fairly obvious on the backside of the rotor. When mine on my old axle started leaking it was a nice greasy mess inside the parking brake area and the tube was damp where it had run down it a bit.

 

[CaptainXL]

If the seals were bad I'd think it would be fairly obvious on the backside of the rotor. When mine on my old axle started leaking it was a nice greasy mess inside the parking brake area and the tube was damp where it had run down it a bit.

Well I took the rear drivers side rotor and that's exactly what I found. Fluid is everywhere. So I guess I need to drain the diff fluid, remove the c clips and axles and then put in new bearings and seals. Should I be worried about using a micrometer to check the axle bearing ride surface to see if it's ground down or just replace the bearings and seals and call it good?

 

[Sparky]

If they are ground down at all they will have pitted first. Any pitting = replace or they'll destroy your new bearings. And don't bother with any of those "axle repair" bearings as they don't last.