# Stuck Rear Caliper Piston



## Stinky999 (Sep 14, 2006)

I was trying to do my rear brakes today, pads and rotors, and ran into a little snag. I could not get the piston to retract back into the caliper. Every other car I have ever worked on, there is a fairly minimal amount of effort required to push the piston back into the caliper. In most cases, I simply squeeze it back in with a big pair of channel lock pliers. I wound up trying the large C clamp route. No dice. As a matter of fact, I had to put so much force on the clamp to twist the screw, I wound up bending the handle on the clamp. This isn't normal.
So, is there something "unique" about the Phaeton rear caliper that I am missing? Should I assume the caliper is frozen? This seems very unlikely given that the caliper appeared to be working fine. There was no abnormal wear pattern on the rotor, etc. I understand there is a VW/Audi tool for compressing the piston. Is this tool intended to put "herculean" force on the piston?
Any insight would be appreciated. Thanks.
Roger


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## Phat One (Jul 10, 2009)

*Re: Stuck Rear Caliper Piston (Stinky999)*

You have to turn the piston as you squeeze it back in. Did you try that? You can get the tool from somewhere like Autozone for 20-30 bucks.
Graham


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## Stinky999 (Sep 14, 2006)

*Re: Stuck Rear Caliper Piston (Stinky999)*

No, but I'm not sure that this would keep the piston from retracting though. I also looked at the official VW/Audi piston retractor. It only has a hand turned knob on the end. There is no way this could apply enought force to push in the piston. I had the C clamp squarely on the piston, applied an extraordinary amount of force, and didn't budge. Again, I've done dozens of brake jobs on all kinds of cars and never experienced anything like this before.


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## PanEuropean (Nov 3, 2001)

*Re: Stuck Rear Caliper Piston (Stinky999)*


_Quote, originally posted by *Stinky999* »_...is there something "unique" about the Phaeton rear caliper that I am missing?

Hi Roger:
I believe that there is some kind of special procedure (not too complicated, but "unique", as you put it) applicable to work carried out on the rear brake calipers.
I have never done this kind of work before, so, I can't help you based on my own experience. You might want to browse through the post entitled Brake Service, Overhaul, Brake Pad and Disc (rotor) Replacement and see if you find the missing kernel of information there. That is a fairly long post (5+ pages), but I think there are reports by folks who have done their own brake servicing in there - or perhaps archival notes that will lead you to a discussion about doing your own brake component replacement.
Michael


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## Stinky999 (Sep 14, 2006)

*Re: Stuck Rear Caliper Piston (PanEuropean)*

OK, it looks like I needed to turn the piston while I applied pressure (Phat One was right). I'll get the Harbor Freight tool and give it another try.


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## flyin_vr6 (Jan 16, 2007)

I got mine all apart and then realized it required a special tool that none of the local auto parts stores carried. I need my car for work and couldn't wait for a tool to come in the mail so I improvised. It is possible to retract the piston with a large C-clamp and a large pair of Channel locks. It's tedious but it works. Tighten, turn, tighten, turn, repeat.... Be careful of the boot with the pliers though. I was able to get it retracted in about 10-15 mins.


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## cai (Mar 22, 2009)

*Re: Stuck Rear Caliper Piston (Stinky999)*

I recall having to "sort of" screw the piston in for the rear brakes on an old Audi I have. The piston would not go straight in with only force applied. I do not recall having to apply much pressure while turning, I think the piston just about screwed in with almost no effort. The trick was finding a way of clamping on the piston to turn it.
cai


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## Stinky999 (Sep 14, 2006)

*Re: Stuck Rear Caliper Piston (cai)*

I bought the tool. I'll try again this weekend.
I still can't visualize how the spiraling is effected inside the caliper. The bore has to be smooth, or the seals won't hold pressure. There must be some sort of threaded, expandable shaft pushing up on the bottom of the piston. Weird.


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## dlouie (Oct 31, 2008)

*Re: Stuck Rear Caliper Piston (Stinky999)*

The rear caliper is no ordinary caliper. Most of the German cars I've worked on have an integrated disc/drum setup for parking brake functions. The Phaeton apparently has the parking brake function integrated into the caliper. It probably was not a good idea to try to force the piston back. If it that process warped your tool, then it could certainly have damaged the caliper also. It would be prudent to check it carefully. See the attached for more info. It's from the self study guide and I'm not sure if it applies to all Phaetons, but it could be a clue. For those who don't do their own work, beware of taking your Phaeton to any mechanic who isn't familiar with Phaeton as it is obviously not an ordinary car and stuff like this can get really bad in a hurry compromising your safety. So... there was a guy who swapped out his brakes for an aftermarket set... I wonder how he retained the parking brake function?
I couldn't attach the pdf so here are the images:
























Damon


_Modified by dlouie at 9:13 AM 11-4-2009_


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