Paging Rick and Gary T. and anyone else who might have experience with rear disc brakes on a Ford!
About a year ago, I did a complete brake job on my Freestar. When I tried to compress the pistons on the rear calipers, they wouldn’t compress. I had the tool to turn the piston, but it didn’t work. I went to a parts house to get new calipers, put everything back together, bled the brakes and everything was fine.
As soon as the brakes started to wear down a bit, I started getting a “clunk” sound when I hit the brakes, coming from the rear. This turned into a rattle, which stopped when I stepped on the brake or pulled up the handbrake a couple of notches.
I took everything apart on the rear brakes and everything seemed to be normal. I replaced the 8 anti-rattle clips and it quieted down for a while. Then the rattle and clunk started again.
Now, a year later, the rattle is getting really bad.
I can reach under the car and move the rear calipers around. Everything is mounted properly and tight. But the pistons seem to be retracting when the brakes are off. It seems like the pressure should release when the brake is off, but not actually retract the piston to the point that the calipers float around 1/4". The brake pads are just sitting in the little mounts on the end and rattling around between the caliper and the brake disk.
I’ve bled the brakes multiple times, both the normal 2-person way and with a vacuum bleeder.
At this point, I don’t know what to try next. Is it possible the calipers are defective? It’s happening on the both the right and left sides. Is there something I’m missing here?
BTW, the emergency brake is not the shoes-on-hub type. People I’ve talked to about this keep asking me this. The cable connects to a lever on each rear caliper.
What you’re missing is an understanding of how these particular calipers operate, and the importance of using the parking brake regularly.
The significance of the parking brake design is that it uses the rear pads, just like the service brakes, but operates them mechanically, not hydraulically like the service brakes. There is a mechanism inside the rear caliper to accomplish this.
Let’s go back to a year ago (information for future reference): the way to retract the pistons is to turn them AND press them in. Turning allows the piston to move past the internal adjuster, but turning alone won’t move them, and they will only press in ~1/8" if not turned. You’ve got to PRESS and TURN (back and forth or simultaneously).
Unlike simpler calipers without a parking brake mechanism inside, which self-adjust from just using the service brake, these calipers self-adjust by application of the parking brake – which I’ll bet dollars to donuts has not been used. As the pads wear, if the caliper self-adjustment has not been actuated then excess play will develop between the caliper and the pads. If the parking brake cables and the mechanisms inside the calipers have not seized from lack of use, you can solve your problem by repeatedly actuating the parking brake until the pistons are adjusted out to their proper position.
I’m curious as to why you replaced the rear calipers on an '05 in the first place. You’re saying you couldn’t roll back the pistons on your original calipers? I didn’t quite grasp that.
I’ve never worked on a Freestar, but I’m pretty familiar with brake systems.
Do these calipers have a spring to assist with piston roll back?
Are any warning lamps on? Specifically ABS or BRAKE?
Do the pads fit tightly in the brackets? Could be wrong pad size?
yeah, GaryT is on this. The set of caliper tools I used to have had a special plate for Ford rear calipers that would press and turn the pistons simultaneously; the pad face of the piston has two slots in it which were engaged by a pair of pins on the tool’s plate.
The pistons wouldn’t retract. I was using the tool to turn them and putting pressure. This isn’t some kind of press that turns them and puts pressure at the same time, it’s just a tool that fits into the grooves on the piston that you attach to a ratchet. I put the caliper in a vice and pushed hard while I turned. The piston turned, but wouldn’t retract.
I was in a hurry, it was getting late, and had to leave on a trip the next morning, so I found a set of calipers in stock for like $60 each, and I went and got them.
No, I don’t regularly use the parking brake. The parking brake works fine, and I can start using it every time I park, but someone suggested this almost a year ago when the problem first started and I used the parking brake for about a month and it didn’t solve anything.
If any of the parking brake mechanisms were frozen, the parking brake wouldn’t work at all, right?
Okay, it looks like you did know what I mentioned, sorry if I appeared condescending.
On pushing the piston in: I have to figure either the mechanism inside the caliper was seized, or the piston wasn’t being pushed in hard enough. Seized mechanism, replacement is the fix. How hard to push? I don’t push by hand. My tool lets me put a wrench on a hex to rotate the piston, then has a screw to push it in (I alternate – turn the piston some, then screw it in some, back and forth). Sometimes I can turned the screw’s knurled handle by hand, other times I have to use pliers on the screw to turn it – and this is with the mechanical advantage (leverage) of the screw threads. Even simple calipers won’t push in by hand, I use giant Channellocks (460, 16" long) to do it. If you were using just muscle to push on the piston, that probably wasn’t enough force.
On adjusting by using the parking brake: I know there are some GM designs where this applies, I was assuming it was the same with your car. My repair info does not address this detail, so I can’t be certain, but the symptom you described is identical to what happens on the GM products. As to why operating the parking brake didn’t seem to avoid/solve the problem, I’m afraid I don’t know. So far I can’t think of anything else that would explain your situation.
On the parking brake working: One frozen cable might prevent one side from working but not the other (depending which cable). The caliper mechanism might work in terms of applying the parking brake yet not work in terms of self-adjusting (those mechanisms are a bit complicated). Still, my expectation would be that with calipers just one year old, it all should work. I would suggest, if you haven’t tried it yet, to operate the parking brake on-off a hundred times or so and see if there’s any reduction in the amount of play.
There’s a pretty good possibility that I wasn’t putting enough pressure to compress the piston. The tool I had is just a little cube shaped thing that has a square hole to put a 3/8" drive ratchet in it on all 6 sides. Each side also has a pattern of little pieces that stick out that will fit into the various pistons. Mine had two notches at each side of the piston, and of course, no side of the universal tool had that pattern, but one had 4…two of which lined up with mine, so we modified the tool with a grinder. Unfortunately, the tool doesn’t give ANY type of leverage when pushing in on the piston beyond putting the caliper in a vice and leaning into it. There’s really no way to put any type of clamp on it and still be able to turn it.
Someone I spoke to in the process of doing all this told me that there’s an internal sleeve that the piston screws into and they can break free, so turning the piston is also turning that sleeve and you get nowhere.
I was in a rush to get the job done because I had to leave for a 1500 mile trip the next day, so I ran out an bought new calipers.
Anyway, I noticed today that when I pull the parking brake all the way up (it’s a handbrake) with the button pushed in, at the top end of the pull, I can feel a little resistance and can hear a faint click coming from the rear end. I don’t know if this is the activation of the adjuster. I have to pull the handle WAY up to get it to do this. Even if I had used the handbrake on a regular basis, I probably wouldn’t have pulled it this far up because there’s a lot of resistance. I pulled it a dozen times or so when I parked tonight, but I don’t know if that did any good. The handle is awkward to pull in any case, and after a dozen pulls, I felt like I’d been on some kind of strange workout machine at a gym.
I’ll see what it does in the morning and maybe see about pulling it a hundred times and see what happens.
I suspect the click is the adjustment occurring. I was going to recommend a cable adjustment, but my repair info says there is none. I’d try for a hundred clicks, and if that makes a difference continue until it won’t click any more (or it’s obvious that all is working well). If lack of caliper adjustment is the problem, then I expect when all is in adjustment the handbrake lever will stop firmly before it gets all the way up.
