front piston damage

[jvandyke]

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?

[ungermm]

I wouldn't think you could get damage there. What kind of damage are you talking about.

[wrench459]

If its just oh let me put a number out here <15 percent of the ring it should be ok.
But hey thats the dudes that bring you to a halt!!
You can go like a bat out of hell BUT if you cant stop your in big trouble
fudge on alot of places but not the brakes IMOA

[GTJIM]

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.

[jvandyke]

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"

[willis]

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 )

[jvandyke]

Originally Posted by willis 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. ( just my way of thinking )

Ya think? The area below the lip (the important part) has some brake fluid and PB blaster on it from me in my take apart attempts.

[willis]

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.

[GTJIM]

Before getting too enthusiastic dismantling them check to see if your local RockAuto or AutoZone has exchange rebuilt calipers.

[namba209]

Originally Posted by GTJIM Before getting to enthusiastic dismantling them check to see if your local RockAuto or AutoZone has exchange rebuilt calipers.

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.

[kwilford]

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

[jvandyke]

Originally Posted by kwilford 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

This is what i tried to do last night but the piston only goes as far as you see then it moves a tad out but settles back again as my daughter pumps the pedal (i had a big C clamp holding the other piston in). Just won't go "over the hump" Maybe not pumping pedal vigorously enough.

[jordan]

Is the brake fluid reservoir full? Unless you are loosing fluid pressure or are low on fluid the MC will push out the piston like nothing.

[jvandyke]

Originally Posted by jordan Is the brake fluid reservoir full? Unless you are loosing fluid pressure or are low on fluid the MC will push out the piston like nothing.

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.

[kwilford]

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

[opelwasp]

For $63 at partsamerica.com I'd just get new ones. Raybestos rebuilds are usually pretty good.

[GTJIM]

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!

[biglefti]

Originally Posted by jvandyke 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.

It sounds like you have air in the system and it is just compressing. If you bleed the system of the air, you should be able to push the piston out with the pedal until it starts to leak brake fluid. By then you can remove it by hand.

[markandson]

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.

[jvandyke]

Originally Posted by kwilford 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

This ended being what I did. A bit more vigor with the pedal one piston came out cleaned it up a bit, put it back, moved the clamp, pumped the other one out until both were touching in the middle, teased one back in and the other out until it came out, then teased the last one out. I used flat screw drivers and tapped gently with a hammer first on one side then the other until it came out. cleaned up, new seals intalled (BTW one of the old ones had a very noticable bevel to it, the other did not. The new ones from my rebuild kit (Beck Arnley) appear symetrical in cross section. I hope these are the correct ones and provide the pistons with the proper "reverse friction". Pistons look fine other than slightly mucked up edge on both of them. No shims available. I'll try another brake shop tomorrow, maybe they'll have a clip too. Almost there. I hope it's okay to rebuild one caliper and not the other (yet).

[kwilford]

Originally Posted by markandson