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#1 (permalink) |
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Opeler
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Unanswered: front piston damage
I've almost got the pistons out of my caliper but both edges of both pistons, that part that pushes on the pad has damage. Is there a source for just the pistons? Wonder how that happens?
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"Being ignorant is not so much a shame, as being unwilling to learn." Benjamin Franklin
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#4 (permalink) |
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4246 Post Club
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Spares ....
Opel did supply the pistons as spares - PN 3434322 for all 1.9L GTs 69-73
There are two sizes of caliper pistons - one for 1.1 (45mm) and the other for 1.9 (48mm) GTs. I have a set of the smaller ones for my Kadett off EBay. I would suggest trying a BMW dealer if OGTS have none - they are ATE brand calipers usually and both BMW and VW used similar calipers in their range. Otherwise they can be made - done here out of stainless steel! - or scavenged from other caliper sets. Did your calipers have the anti-vibration shims between the pads and the pucks (pistons)? Without them the pads will rattle against the ends of the pistons and eventually damage them. I guess you could even get the pistons ground flat again - the outer ends are usually 'crowned' by the damage you see. |
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GTJim
Opel Owner since last Century! Copyright © 2000-2008 J D Henry All Rights Reserved |
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#5 (permalink) |
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Opeler
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no anti-rattle shims
not as bad as I thought at first, I just figured out that part of that rim is supposed to be missing but a bit, small bit, is chewed a little, even a tad of the rim hanging there BTW how are you supposed to get the pistons all the way out? I clamped one and since I don't have a compressor (yet) I reattached it to the brake line and pushed the other this far but it won't pop all the way out just moves a bit, then settles back, don't know what I'll do if I get one out I don't have the "special tool J-22429"
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"Being ignorant is not so much a shame, as being unwilling to learn." Benjamin Franklin
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#6 (permalink) |
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Opeler
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Looks like you have the same problem I do. The sides of your pistons have rust and bubbles under the chrome on them. That makes them junk. The pistons need replaced for sure. For me, this gives me a good reason to upgrade to larger and better brakes. Stopping fast is much more important than going fast. ( just my way of thinking )
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#8 (permalink) |
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Opeler
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Yea, sorry but with the top lip missing that means that the rubber boot that is around the piston will not work and water will get inside there. The big problem is when you put new pads on the rusted area of the piston will be pushed below the seal in the caliper. When that happens it makes the piston want to stick and the brakes will drag. Most of the time the caliper can be saved if you have new pistons. If you pull out the square seal in the caliper I am sure you will find a bunch of white junk that is built up in there. All that needs scraped out before you put in new seals. It is not hard to fix, it just takes a bit of time.
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#9 (permalink) |
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4246 Post Club
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A Thought
Before getting too enthusiastic dismantling them check to see if your local RockAuto or AutoZone has exchange rebuilt calipers.
Last edited by GTJIM; 04-15-2007 at 01:25 PM.. |
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GTJim
Opel Owner since last Century! Copyright © 2000-2008 J D Henry All Rights Reserved |
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#10 (permalink) |
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6,000 Post Club
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Two things here, that square o-ring is a bear to find if you do disassemble the calipers. If your local auto parts store doesn't have them, give Gil or Dennis at OGTS a call Monday, you can get a set of packed, that is rebuilt calipers, complete with pads, pins and the anti-rattle shims. If you just wanna go with new pistons lemmee know, I've got the old shims out of Willit? laying around with a bunch of other stuff I didn't re-use.
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Ron
72 GT 3.4L V-6/T-5/ZF posi - almost done - Just need AC installed. ![]() 75 Chevy monza 5.7L/TH350/Auburn 3.08 posi - Next |
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#11 (permalink) |
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Über OpelGT.com Moderator
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It's not absolutely clear in the photo, but IMHO, the piston looks fine and should clean up with some very fine polishing of the sealing surface. The lip looks intact to me, so I don't understand that comment. The small chamfered edge is normal; make sure you re-install the piston with the chamfer at the correct angle (refer to the FSM).
As for removing the pistons, I have typically used compressed air through a blow gun with a rubber tip against the brake line connection. Be CAREFUL! Don't get your fingers between the piston and the caliper as it can eject with a BANG! Another technique is to use master cylinder to force the piston out. Leave one caliper in place with the pads against the rotor, and the other off the hub. When you pop the first piston out, it will spray brake fluid around so wrap it in rags. Then clean up that piston so it slides in and out easily, slid the piston back in and clamp it in the retracted position (or temporarily re-install the pads against the rotor). Then pop out the other side. HTH |
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Keith Wilford
working on my '71 GT and '75 SportWagon |
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#12 (permalink) | |
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Opeler
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"Being ignorant is not so much a shame, as being unwilling to learn." Benjamin Franklin
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#14 (permalink) |
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Opeler
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Yes but that's not to say a leak hasn't developed somewhere else in the system. I pumped pretty vigorously and it didn't pop out the piston. Will try again. Checking for leaks and such.
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"Being ignorant is not so much a shame, as being unwilling to learn." Benjamin Franklin
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#15 (permalink) |
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Über OpelGT.com Moderator
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I thought you were having trouble with the other side. With the piston that far out, just pry it the rest of the way. The bottom has probably passed the seal and just needs to be "helped" the last 1/4 inch or so. You can use the outer sealing groove to pry it, with a couple of flat-bladed screwdrivers to lift it evenly. Don't get TOO rough with it, but if it has come that far, it isn't seized.
Then clean it up, re-insert it (temporarily) and repeat for the other side. Remove the remaining piston by prying up on the groove. When you get both pistons out, polish them with #400 or finer wet/dry, clean up all the machined surfaces, and install new seal rings into the calipers, and new dust covers. Follow the FSM and you'll be good to go. HTH |
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Keith Wilford
working on my '71 GT and '75 SportWagon |
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#16 (permalink) |
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Non Civilian
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For $63 at partsamerica.com I'd just get new ones. Raybestos rebuilds are usually pretty good.
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Some People Are Like Slinkies. They're Not Really Good For Anything, But They Bring a Smile To Your Face When Pushed Down The Stairs."
![]() Remember: Advice and Opinions are free, take it for what it's worth. Caution: Driver carries less then $20 of remorse. |
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#17 (permalink) |
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4246 Post Club
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PartAmerica
Online Auto Parts and Auto Accessories Store at PartsAmerica.com do list them - they want a $30.00 core charge though so they need your old calipers in exchange.
They also list new discs, rear wheel cylinders and master cylinders plus pads and relined rear brake shoes - treat yourself! Last edited by GTJIM; 04-15-2007 at 02:40 PM.. |
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GTJim
Opel Owner since last Century! Copyright © 2000-2008 J D Henry All Rights Reserved |
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#19 (permalink) |
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Senior Contributor
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The missing part on the piston is probably from a PO trying to pry it out with a screwdriver, instead of using pressure to eject it. You should not have to "pump" the pedal to push the piston out, it should come out a little with each push of the pedal, and not return very much each time. As previously stated, air in the system can cause this method not to work. I used compressed air, held the other piston in with a C clamp, put a thin block of hardwood in between to avoid damage to the piston, and put 100 psi on it. It darn near flew out, very dangerous to fingers, be careful. BTW, the caliper was in the vice in my shop when I did this, not on the car.
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Jeff
'73 GT,5spd,Recaro,EDIS4 2.2 EFI by MegaSquirt,15" Wheels,Lecarra,F&R Sway Bars,Custom Exhaust,1" Sport Spring,Koni Reds,Big Brakes,3 Core Ali Radiator,Hse of Colors Kandy Pagan Gold. '64 VW Karmann Ghia '08 BMW M3 |
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#20 (permalink) | |
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Opeler
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"Being ignorant is not so much a shame, as being unwilling to learn." Benjamin Franklin
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