Sticking front caliper conundrum.

[Nuvo]

Bit of a strange one this, well, it is to me at any rate.

The car was showing symptoms of a sticking front left brake, i.e., very hot disc compared to the right hands side and increased pad wear on the inner brake pad.

I'll cut a lengthy story short to say that I rebuilt the nearside caliper using new seals and bled the caliper without to much trouble.

I put the wheels back on with the car still raised on axle stands. I started the car and selected first gear. The left wheel can be seen running freely now but the right wheel is sticking.

The right wheel can be turned by hand but with more resistance than the left.

Any idea why this should happen and what I need to do to fix it?

Thanks in advance,
Rob.

[Mikes2]

normally both calipers should get done at the same time

[Nuvo]

I Agree. Ideally that's what I would have done. But on this occasion I thought it would have been sufficient to rebuild the problematic side only. Maybe my decision to not fix what isn't broke wasn't a good one in this instance.

[Nuvo]

Just an update to this fun filled adventure. I stripped down and replaced the seals on front right caliper and bled the air out of this side too.

A quick few pumps of the brake pedal to settle the pads then and start up the car and select first gear as before.
Now I'm back to seeing the front left wheel stuttering as seen from the outset. Lightly depressing the accelerator is sufficient to overcome the friction.

So I then decided to replace the piston as some of the chrome below the gaitor (the groove in which the dust boot sits in) is missing. The level of corrosion seen was fairly minimal and I originally thought that it wouldn't interfere enough with the square cut O-ring in the piston bore to cause a problem. Fitting the new piston didn't improve the situation as I suspected.

After all of this I am beginning to wonder if this might actually be okay and whether a little bit of wear on the new pads would sort this?

Please share your pearls of wisdom.

[stocious]

i just did a stuck calliper for a neigbour and its cured the hub, but noe the d/s hub is sticking dragging. weired one. clean the disks both sided's and check for warpage whit a a screwdriver on the carrier bracket and rotate disk if warped much it will touch in spots and clear in other. other that that apply copper grease on on contact to carrier area on pads. fixed a few syptoms like this by just cleaning things. possible that a break hose/s could be interianaly brok down and there lining is now detaced and resrtiction flow out of calliper.. hope it help in some way. vicegrips clamping brake pipes when calipers are off causes these hose failure

[Nuvo]

Thanks for the reply.

I have applied fresh grease to the carrier guide pins and filed the surface corrosion off the areas which come into contact with the brake pads and lubricated them with some copper grease.

The flexi hoses were fitted by me some time ago so I know they have never been clamped with grips. I always cap the ends to stem the flow. The flow of fluid is unrestricted when pressure bleeding each side.

I've still to check the discs for run out. I'll look into that the next chance I get.

The only other thing I can think of is that it is the piston bore is the cause of the problem. I mention this because I wasn't able to push the piston fully home using just my hands when it was properly seated into the bore seal. I had to use a G-clamp to assist me. It only need a gentle turn to fully retract the piston.

I used a small electric tyre compressor to supply air directly into the hose inlet of the caliper to check for leaks and check piston operation. It was leak free but the piston wouldn't extend. So I resorted to reconnecting the caliper to the hydraulic circuit and testing it on the car. The piston extended okay using this method.

In my limited experience I would have thought that I should be able to push the piston fully home by hand and extend it with a compressed air supply. I'm a bit baffled by this as the bore was thoroughly cleaned and lubricated with brake fluid and it was free from scoring.

[Mikes2]

That's normal - it's very rare to be able to push a piston by hand.

New caliper may be needed

[Nuvo]

Thanks Mike. I'm beginning to wish I'd just bought a new caliper in the first place.

[Nuvo]

Well, My faith has been restored, both in my car and my abilities.
I was able to fix the sticking by running the car several times up and down the length of the car park and applying the brakes firmly but not bringing the car to a complete stop. Presumably this must have been sufficient to remove any high spots on the discs.

I'm feeling rather pleased about closing this chapter.