Brake Caliper Rebuilding

[George7941]

I got a surprise when I switched from snows to summer tires and noticed that the front right inner(against piston) brake pad was worn about 70% whereas the other three pads were worn about 50%. IR temperature measurement shows front right rotor running a bit hotter (10C) than front left.

The caliper is not binding much because the right wheel offers about the same resistance as the left wheel when spun after jacking up and applying the front brake once.

Truck has 122k km (75k mi) and these are the original pads. I flushed the brake fluid once about three years ago and am planning to do it again soon.

Would rebuilding the caliper myself likely solve the issue? RockAuto has the square cut seals and the dust boots for about $5. Should the bores(twin piston) be honed if there is corrosion? I am thinking of picking up a used caliper from a wrecker and rebuilding it so that I can just switch calipers without losing much fluid and then having to do a ABS bleed.

 

[Merkava_4]

Originally Posted By: George7941
Should the bores (twin piston) be honed if there is corrosion?


Yes you should, but the question is, how much metal is allowed to be removed...

 

[Cardenio327]

Since the truck is only eight years old and you have already flushed the brakes once I wouldn't be in so much of a hurry to condemn the pistons, bores and seals.

It is more likely that you have a bent, worn or rusty pin. I would leave the hydraulic side alone except for flushing it again. I would go ahead and put two new hardware kits on. You might want to clean out the bores that the pins go in by hand with an old drill bit. Be sure to lubricate everything that moves with an ultra high temperature brake grease.

If you do decide to do the hydraulics I would go ahead and install all new pistons. If there is rust or pitting inside the bores, don't worry about it, on calipers the sliding surface is on the piston, not the bore. If you have to replace one piston, be sure to replace all of the pistons on both sides, the material the replacements are made of is usually different from the originals.

 

[George7941]

The caliper floats freely on its pins, it can be easily moved back and forth. The pins are rust free and well lubricated. If the caliper wasn't floating freely the wear would be on the outside pad, not the inside pad. Same with sticking hardware, wear will be on the outside pad.

Thanks for the tip about pistons. I will pick up a used caliper and take it apart and then decide if new pistons are warranted.

 

[Donald]

Look up rebuilt calipers on RockAuto. Some are pretty cheap. Your caliper could need to have the cylinder honed, chrome plating on piston corroding off.

How about the rails where the tabs of the pads move on? Nice and smooth and slightly greased?

 

[JHZR2]

Originally Posted By: Donald
Look up rebuilt calipers on RockAuto. Some are pretty cheap. Your caliper could need to have the cylinder honed, chrome plating on piston corroding off.

How about the rails where the tabs of the pads move on? Nice and smooth and slightly greased?


Beware of the cheapies. I recently had a thread where the rebuild rusted severely in just a couple months, and looked far worse than the original did after 23 years.

 

[George7941]

The problem with rebuilt calipers is the core charge. Shipping charges to return the core will be high from Canada and a 13% tax gets added on to the core charge in addition to 13% on the cost of the rebuilt caliper itself. For my truck, at RockAuto, the core charge is more than the cost of the rebuilt caliper itself for a lot of the calipers listed. The cores must be in short supply. Perhaps an indication of a trouble prone part with a high failure rate? New calipers are about $130.

As stated in a previous post the caliper floats freely on its pins and the pads float freely on the locating hardware.

 

[Tegger]

Originally Posted By: George7941
As stated in a previous post the caliper floats freely on its pins and the pads float freely on the locating hardware.

Step on the brake pedal to eject the piston most of the way out if its bore (careful not to eject it entirely!).
Or, if you can grab it with Channel Lok pliers, rotate it and pull it most of the way out of its bore.

Pull back the rubber dust boot. Do you see anything like this on the piston?
(these are rear caliper pistons, but the idea is common to all)

 

[George7941]

I won't get to it for a few days. I will pick up a used caliper first, disassemble it and check the condition of the piston.