Brake pad bracket behaviour

[454Casull]

How much spring return are you supposed to get from the pins in the pad bracket? The front-left corner of my car has pins that behave normally (I think) that really want to push the pad bracket away from the caliper pistons. However, the front-right corner of my car has pins that don't really push much (in fact, one of them doesn't push at all once it's fully retracted; it just doesn't move). The pins themselves all slide well, but the dust boots don't all behave the same way... I guess they're fatigued?

Is this a big deal? Do I need to replace the pins and boots on that corner, or in the worst case, the bracket?

 

[The_Jeff]

I'm puzzled by your description but concerned that one side is not like the other. What car is this?

Are you sure you aren't describing some sort of anti squeal/rattle spring?

If you can access an infared thermometer you can go for a drive and see if one rotor is much hotter than the other. That would imply either dragging or uneven braking.

 

[454Casull]

I'm pretty sure I'm not talking about those springs. The pad kit called them abutment clips, anyway.

It's a 2005 Cadillac CTS /w standard suspension. What part of the description was not clear?

 

[bullwinkle]

The return action of the master cylinder should pull the piston back into the caliper-possibly there is a brake hose collapsing or the caliper is hanging up?

 

[kevinf]

The caliper pins are just sliders. They shouldn't push anything. They just allow the caliper to stay centered as the pads wear.

 

[454Casull]

Originally Posted By: bullwinkle
The return action of the master cylinder should pull the piston back into the caliper-possibly there is a brake hose collapsing or the caliper is hanging up?

Ah, I didn't know that the caliper pistons have a self-returning action. I thought the caliper pins pushed the bracket (and therefore the pads) away from the pistons.
Originally Posted By: kevinf
The caliper pins are just sliders. They shouldn't push anything. They just allow the caliper to stay centered as the pads wear.

If this is the case, by what means do the pins center the pads? The pistons would then be the only force in the system, and once retracted, the pads would basically drag on the rotor, yes?

 

[mechanicx]

As long as the calipers pins move freely and the boots aren't torn or letting grease escape, they are probably fine. The pins are just to allow the caliper to slide and don't provide any real "push" to the caliper. The pads slide on the pad anchor and are clamped by the caliper. When the brakes are applied the pads and caliper can slide together but the pads are sliding on the pad anchor and the caliper is sliding on the caliper pins.

 

[454Casull]

The next time I have the assemblies apart, should I remove the boots and give everything a deep cleaning and regrease fully?

Also, what is the optimal amount of grease inside the pin bores?

 

[The_Jeff]

I've had issues with the grease hardening up and or mixing with brake dust, rust and grime at the bottom of blind pin holes. You don't want so much grease it hydrolocks, because then one pin jams before it bottoms out before the pads wear out, then you get a pad that jams at an angle and brakes poorly. When I do brakes I pick the old goo out of the holes with a drill bit, spraying a little brake cleaner in there to loosen it up.

I do try for a decent glob of grease on the pins near the little rubber bellows to defend against water ingestion and corrosion.

 

[The_Eric]

You're experiencing air in the slide pin holes. It's being sealed in by the grease and boots. That's what is pushing the pins back out.

 

[mechtech2]

The pins should be cleaned perfectly and lubricated .
But there should be NO spring return from them!
The slight return of the piston is from the seal flexing a tiny bit, and returning to it's original position when you release the brake pedal.

 

[454Casull]

Originally Posted By: The_Eric
You're experiencing air in the slide pin holes. It's being sealed in by the grease and boots. That's what is pushing the pins back out.

Makes sense, though the self-accordioning action is very strong in a pair of boots on one corner of the car.

If this is of no concern (the car drives and brakes straight) then I'll pay it no mind.

 

[454Casull]

Originally Posted By: mechtech2
The pins should be cleaned perfectly and lubricated .
But there should be NO spring return from them!

How do I fix this? As far as I can tell there is no easy way to suck the air out of the pin bores.

 

[kelpie]

If you're heating up on one side, or if the car is pulling while braking, you probably need a new flexible hose (from the caliper to the metal line). For example, if the car is pulling to the right, the left hose is collapsed on the inside. When that happens, the left caliper will usually overheat due to it dragging because it can't let the fluid back out of the caliper due to the collapsed hose. Sometimes, the problem is a bad caliper, but more times than not it's the flexible hose gone bad. For sure if you decide to replace a caliper, replace the flexible hose too.

 

[MontyD]

Pushing the slide pin all the way in the bore and then gently lifting the sealed area of the boot to expel the trapped air is the recommended procedure.

If it is still sucking air in the boot afterward, then more than likely the boots are drawing in air from a bad boot seal when being moved.

 

[mechtech2]

Suck the air out of the pin bores??
Just install them .

Besides, any pressure or vacuum in them would work BOTH ways, with no braking effect.