Yet another brake question

[supton]

Since the Camry had a sticky brake pad, I decided to check the pads on the VW since I needed to do a tire rotation.

Is it a bad sign when you have to hammer the pads off??? I mean, literally, I had to use a screwdriver as a chisel and whack away at it, they were stuck in place that badly. [Sliders are just fine, go figure.]

Worse is the fact that I knocked rust off the rotor surface, so it'll never be smooth again. So I am up to new pads and rotors. Despite the pads being only half worn. I *think* these rotors are only 3 years old / 80kmiles, the pads are about 4 years / 120kmiles. I guess on an age basis it was about time.

Worst is the fact that the pitting on the rotor indicates that the rear calipers are not working. I don't have the proper windup tool, so I tried a basic test: I used a screwdriver, and tried to get it just right, to see if I could make it spin, even just a little. Nada.

So, my question is, shouldn't these pistons turn relatively easy? Or do they really need force? Last time I did this one side was easy, albeit with the tool (the other side was shot--what is it with VW calipers? this car has always gotten brake flushes every 2-3 years).

I am not looking forward to changing calipers. I'm tempted to put it all back together and let someone with the tool to make the ABS pump work do this. I've thought about getting VAGCOM to do this sort of work, but at $250 I've held off.

 

[Sawdusted]

Originally Posted By: supton


So, my question is, shouldn't these pistons turn relatively easy? Or do they really need force? Last time I did this one side was easy, albeit with the tool (the other side was shot--what is it with VW calipers? this car has always gotten brake flushes every 2-3 years).


Depends on the spring rate and the amount of runs on the piston. I would also slide some grease or brake fluid on the piston when rotating the piston. Yes it takes some force. That is why they sell tools to help you rotate the piston.

It takes more force than a regular screwdriver with bare hands can give.

 

[supton]

Ah, so I should get the tool first, and then re-evaluate? Could do that, need to run to the parts place anyhow for pads&rotors if I want to finish this job this weekend.

 

[Falken]

The tool is cheap. It looks like a box with 2 pins on each side that clicks on to a 3/8" drive ratchet or extension.

 

[tommygunn]

Consider Centric Premium rotors. They have a black coating to deter rust.

 

[Sawdusted]

most auto parts stores will let you rent them for free (with deposit).

 

[Tegger]

Originally Posted By: supton
Is it a bad sign when you have to hammer the pads off??? I mean, literally, I had to use a screwdriver as a chisel and whack away at it, they were stuck in place that badly.

This is VERY bad. You have tons of rust somewhere that's clamping the pads in place.

Originally Posted By: supton
So, my question is, shouldn't these pistons turn relatively easy? Or do they really need force?

Should be really easy to turn, as in one-handed. You can't turn your pistons because they are rusted. And a screwdriver ought to be just fine for turning the piston.

This is the most likely reason your pistons are seized and are un-turnable. See the rust below the groove?

 

[supton]

I hammered it back together, just to sorta button things up for the night. The stainless shims appear to have thick rust layers on them, once scraped off things slid better. Was no fun sliding the caliper back in place though. I suspect the caliper is toast.

What I find odd is that the rust was under the braking surface. Like in the center of the braking surface.

 

[WhyMe]

open the bleeder and they should be easier to turn in.

 

[Tegger]

Originally Posted By: supton
I hammered it back together, just to sorta button things up for the night. The stainless shims appear to have thick rust layers on them, once scraped off things slid better.

Do it RIGHT! Get rid of ALL the rust!

Originally Posted By: supton
Was no fun sliding the caliper back in place though. I suspect the caliper is toast.

Peel the dust boot back and check for rust, like this:

The caliper is almost NEVER "toast" unless the parking brake mechanism has been compromised by water (which is rare). the PISTON is usually rusted which, if you're a true gearhead, is an easy fix.

 

[supton]

That piston is a long ways out--did you turn it out? Mine is most of the way in.

When I get the tool I'll check. I got most of the rust but I really need new shims. From now on I'll be using that grease to cut down on rust.

 

[Tegger]

Originally Posted By: supton
That piston is a long ways out--did you turn it out?

Yes, so that I would be able to more easily observe the rust. As the piston was turned out, the turning got a LOT easier. As you might guess given the location of the rust.

Originally Posted By: supton
Mine is most of the way in.

Note the location of the rust in the photos I posted...

Originally Posted By: supton
When I get the tool I'll check.

You don't need a "tool". A large screwdriver will work, provided you supply enough elbow-grease. Hold the caliper still with one hand and grip the screwdriver hard with the other. You may need to file or grind your screwdriver so as to obtain better bite on the piston. Use common sense.

Originally Posted By: supton
I got most of the rust but I really need new shims.

If the shims are stainless, then you just need some 50-grit emery cloth. Not sure about VWs, but usually it's the caliper mount bracket that contributes the rust, not the shims.

Originally Posted By: supton
From now on I'll be using that grease to cut down on rust.

What kind of grease? Don't use just anything, but use the correct substance. Molykote M77 molybdenum paste is amazing for this purpose.

 

[Donald]

Originally Posted By: tommygunn
Consider Centric Premium rotors. They have a black coating to deter rust.


I have had Centric coated rotors on my Jeep less than 1 year and the black coating is long gone and the sections that I can see that were coated are now rust color with minimal surface rust.

I am hoping being "Premium" there was more too it than a short lived black coating.

 

[supton]

Tackled the other side. Same story. I did use the screwdriver as a chisel and beat on it with a hammer, and got the piston to turn. Quarter turn anyhow. Parking brake mechanism works fine. Really need the proper tool.

Spent half hour cleaning the shims, scrapping rust and filing--don't know why but cast iron rust seems to like to adhere.

Maybe I can eek out another year on the hardware. The pistons should turn out on their own, regardless of rust, right?

 

[Tegger]

Originally Posted By: supton
The pistons should turn out on their own, regardless of rust, right?

I do hope you weren't attempting to drive the piston around using a hammer and screwdriver/chisel. Turning the piston requires steady, sustained hand-effort, not sharp blows.

The pistons will operate to some degree with the foot brake and the parking brake even when rusted, but turning them in may be extremely difficult.

Can you post a photo of what the face of the piston looks like?

 

[supton]

Yes, without the tool it was the only to make them turn. I've thought about running to town, but that means over an hour of driving for one tool. I don't know of any friends who would have it either. It did get easier after a bit.

Face was bad at all. No scaly rust. Only rust is on wear surfaces.

I haven't read up on how to post pictures.