Sticky caliper?
 

I've been battling a repeating problem for the last several months on my 123 coupe. The left front caliper appears to be sticking or not retracting enough. I've rebuilt the front calipers thinking that was the problem. Nope.
Ive changed the brake hoses. No change.
I've beveled the pad material and even ground the metal on the pads thinking the pads were sticking in the caliper. The last ideas helped for a few hundred miles but its coming back again. The wheel bearings appear OK. I didn't seem to get any play in the wheel on the spindle.
I'm getting frustrated to the point of thinking about buying new calipers and pads. But before I blow the dough on new calipers I'd like to get some advice here. Maybe I'm overlooking something very basic?
Any ideas would be greatly appreciated.

What brand of brake pads are you using?

I think they're ATE's but I really don't remember. I didn't have any problem in the beginning when I first installed the new pads. There's still quite a bit of material left.
The issue started a few thousand miles later. It only seems to occur on one side. The affected wheel has more brake dust on it.

On some pad brands, the friction material is exactly flush with the metal backing plate (ie: OE and Textar.) On others, the friction material stops short of being flush (ATE and domestic aftermarket.) I think that this results in the pad tilting slightly and sticking in the caliper.

Do the various manufacturers stamp their brands on them? I don't recall if mine did or not.

Some do, some don't.

I honestly don't remember what brand the pads are. It's just become annoying to hear a constant squeal starting up again from that caliper. Once it starts it only becomes louder.

sounds like rebuilt caliper time.

Tom W

So maybe I screwed something up when I rebuilt them? It was a very simple job. The pistons and cylinders looked fine when I rebuilt them. I even lined up the pistons correctly as they were shown in the FSM.

I doubt you did anything wrong. The bore or piston probably has a sticky place. Fortunately the cure is not too expensive or hard to do.

Tom W

You've made a diagnosis of a sticking caliper.

However, maybe that's not your problem.

Provide the symptoms of the problem (in lieu of the diagnosis) and we'll probably be able to help you with some better advice.

Do thess cars have a front/rear or side to side proportioning valve? You could have something blocking the slight return of fluid keeping pressure on the caliper to appear as if it is sticking.

I started getting a slight squeal coming from the left front wheel again with no brake applied. It's constant and is getting more audible all the time. It really squeals when I hit the brakes and disappears when coming to a complete stop. It doesn't pull at all though.
Those are my symptoms.

Have you compared the right and left? Jack them up and use a fish scale or something to pull on the wheel to see how much effort it takes to turn each one to get a comparison of how much difference in drag there is. Could it just be something causing a squeal and not a true sticking caliper.

no.

Tom W