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Can you push caliper piston too far back in??

Mossyoakglock

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Mossyoakglock Senior Enthusiast

Mossyoakglock

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Can you push a caliper piston too far back into the caliper to where it gets stuck?

 

I was checking my brakes last night and needed to push the pistons back in some and I might have pushed too hard and too far in. Is that possible? I have no pedal pressure and I'm wondering if that's the reason. This is only on the driver's front since that's the only side I was checking.

 

Is there a way to get the pistons to push back out while they are still on the truck so I don't have to take the caliper off and then bleed the system?

 

There should be no air in the lines since I did not disconnect any lines or anything. The only thing that I forgot to do was take off the master cylinder cap before I pushed the piston in. I only had to push the piston in maybe 1/4 of an inch.

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SILVERADOSC540 Senior Enthusiast

SILVERADOSC540

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If you didn't open the system you're fine. Pump the brakes a few times. Brake from a slow speed. If it pulls away from the side you checked, pump them and try again. If soft but straight that's normal after a push back.

Mossyoakglock Senior Enthusiast

Mossyoakglock

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Yea, there is no pull at all. It still stops perfectly straight, just a soft pedal.

 

Won, what would happen if I didn't clamp the hose? I didn't do that the first time when I replaced the pads two weeks ago and it worked fine until last night.

 

As I said, i didn't have to push the piston in that far. Actually it was less than a 1/4". More like an 1/8th probably.

 

Also, if I bleed the system, do I need to bleed all for corners or can I just do the fronts?

Mossyoakglock Senior Enthusiast

Mossyoakglock

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I forgot to add that when the truck is off, I can pump the pedal and I get really strong pedal pressure and it holds.

jdnoble18 Enthusiast

jdnoble18

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I think your truck is doing the same thing as mine did. You need to build your own pressure bleeder and re-bleed all wheels till you get no air bubbles.

Mossyoakglock Senior Enthusiast

Mossyoakglock

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That's what I was going to do since it's fairly easy and cheaper. I'm just wondering how air would have gotten into the system in the first place?

jdnoble18 Enthusiast

jdnoble18

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I don't have a clue, but the same thing happened to me. I was changing pads, pushed the pistons back in, then had to go to town to get the pads. 40-50 mins later put the pads back in and put everything back together and VIOLA! No pedal pressure with the truck on, could build a decent pedal with it off. Me and my Dad tried to bleed the air out of it but ended up driving it to a mechanic and he pressure bled it and got the air out.

How air can get in when you are only changing pads is a new one on me....

Mossyoakglock Senior Enthusiast

Mossyoakglock

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But that did fix your issue though? Pedal went back to normal after that?

 

I might take it somewhere after work and have them bleed it so they can use the Tech tool and bleed the ABS just in case. They will do a complete fluid flush at the same time.

jdnoble18 Enthusiast

jdnoble18

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Yeah, I had to drive on rear brakes only to my mechanic about 50-60 miles away. I got it to him and he pressure bled the system and all was well. I still have somewhat of a soft pedal (could all be my imagination), makes me tempted to get a set of Stainless Steel lines.

Mossyoakglock Senior Enthusiast

Mossyoakglock

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I had a softer pedal when they were working properly but from what I've read that's the norm on the GMT-900's.

 

I'm looking at getting a set of Stainless lines to help firm up the pedal. Gotta get this issue fixed first though.

Mossyoakglock Senior Enthusiast

Mossyoakglock

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Last night I had my wife push the brake pedal down while I watched the caliper pistons and they were moving out like they should. Once I put the wheel back on I spun the wheel as fast as I could and had her apply the brakes and they stopped.

 

That makes me think that air got in the system somehow since everything is working properly and there are no visible leaks anywhere.

Mossyoakglock Senior Enthusiast

Mossyoakglock

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Will I need to have the ABS bled as well? None of the shops around me can bleed the ABS because they don't have the Tech tool.

 

I can only get into the dealer on Friday morning if I want them to bleed the ABS as well but I don't really want to wait that long.

jdnoble18 Enthusiast

jdnoble18

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The shop I took it to didn't have to. I may have been lucky though.

MikeNH Senior Enthusiast

MikeNH

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Did you clamp the brake line and open the bleed? If not, open your wallet.

 

 

This makes no sense. I literally pushed in hundreds of caliper pistons over the years not doing the above process and there was never an issue.

 

OP- I suppose it may be possible you pushed it so far the seal became unseated? I'm guessing here. I always used the compressing tool for it.

Mossyoakglock Senior Enthusiast

Mossyoakglock

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After thinking about it more I don't think so. I had my wife pump the brakes a few times with the caliper off and I noticed the piston moving out very slowly so I don't think it became unseated. I would think that if it came unseated the piston wouldn't move at all.

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