Right front caliper not releasing

slaviers

Original poster
Member
Jul 15, 2012
8
Been having trouble wearing out brakes for last 18000 miles. After first premature wear, I replaced replaced master cylinder, then both front hoses/calipers/rotors/hubs with sensors (getting low speed abs activation occasionally as seen elsewhere in this forum). 4k later front worn out again. Took to pep boys and they said the front right caliper was sticking. Had them replace all 4 pads and rotors and warranty the front calipers. Got a 2yr/24k warranty. 3k later front right worn into rotor again. They warranty it, say they have replaced fluid and flushed and bleed system of air.. Tech told me that caliper will release when bleed at caliper and when line cracked at abs valve, but won't release when cracked at master cylinder. Told me to take to dealer, where they could scan abs system and check (no abs/brake/check engine lights are on). He thought it was abs valve holding pressure on right front.

Took to dealer for scan. They told me the Booster and Master Cylinder were not functioning properly (hydraulic air lock??) and recommended both replacement and flush for a cost of $1154 (!!!). Needless to say I went to dealer, paid $120 diagnostic fee and left ASAP. As noted above, master cylinder already replaced (bench bleed before install). Called Pep Boys for price on Master Cylinder ($75) that they had, but would have to order Booster ($100)

any thoughts anybody (roadie)? could the booster do this? Tech at pep boys seemed to think problem was only with right front dragging (which it is definitely doing) and that abs valve was not releasing that particular caliper. Said they had thoroughly flushed the line and both front rubber hoses have already been replaced and there is no line problem.

at whits end basically everything has been replaced (RF pads and rotors 3 times!) except abs valve ($$ and hard to do) and Booster.
 

MAY03LT

Member
Nov 18, 2011
3,412
Delmarva
slaviers said:
Tech told me that caliper will release when bleed at caliper and when line cracked at abs valve, but won't release when cracked at master cylinder.

Did they crack the inlet line @ the abs module and see if the RF caliper released? Based on the post it sounds like they did the outlet line and then went to the master cylinder, which really narrows it down to a fault in the abs module. The booster would not cause that.
 

slaviers

Original poster
Member
Jul 15, 2012
8
MAY03LT said:
Did they crack the inlet line @ the abs module and see if the RF caliper released? Based on the post it sounds like they did the outlet line and then went to the master cylinder, which really narrows it down to a fault in the abs module. The booster would not cause that.

He cracked line at oulet of abs. caliper released. Crack at inlet or at master Cylinder, won't release. Dealer says booster and master not functioning properly

Dealer says abs ok. But I agree with you about abs, that why I took it to dealer who was suppose to cycle it and check it. I figured the valve was bad or it had junk stuck it. Pep Boys tech said they could cycle it with their tech 2 scanner to see what was wrong. Dealership says the problem is a '' hydraulic lock'' in the booster master cylinder. Told them MC already changed. They wanted $1100 to fix. Told them no because I knew like could change both for around 200
Sorry for the rant. Could the booster or mc hold pressure on just RF caliper? I guess both front could be holding which would be bad mc?
 

McGMT

Member
Jun 17, 2012
621
slaviers said:
Dealer says abs ok. But I agree with you about abs, that why I took it to dealer who was suppose to cycle it and check it. I figured the valve was bad or it had junk stuck it. Pep Boys tech said they could cycle it with their tech 2 scanner to see what was wrong. Dealership says the problem is a '' hydraulic lock'' in the booster master cylinder. Told them MC already changed. They wanted $1100 to fix. Told them no because I knew like could change both for around 200
Sorry for the rant. Could the booster or mc hold pressure on just RF caliper? I guess both front could be holding which would be bad mc?

IMHO it sounds like the ABS is doing it, the MC couldn't hang just one front caliper. If it was both then yea, but just one, no. And the fact that cracking it open after the abs controller released it shows even more.

When you change brakes is the one harder to push back in than the other?

Just givin my opinion, gotta run n don't have time to check the sheets...

POW! I just had a thought, it kind of hurt actually lol. Anyway, the ABS controller has a "Pre-Loader" that sets it up to take up the air-space between the pad and the rotor so when traction control, stability control and such is activated it can actually apply the brakes. Either way I think you have a wonky ABS block and they aren't going deep enough to identify the problem. What year is your vehicle, just would like to know so we know if it has stability or not.
 

MAY03LT

Member
Nov 18, 2011
3,412
Delmarva
slaviers said:
He cracked line at oulet of abs. caliper released. Crack at inlet or at master Cylinder, won't release. Dealer says booster and master not functioning properly

If they cracked the correct inlet, and the caliper didn't release, I suspect something with the abs module. I'm not sure why they even bothered going up to the master cylinder after the inlet didn't release the caliper. A restriction downstream from the m/c would give them the same result. Not only that but the abs module has a dedicated RF outlet, so a m/c fault should lock more then one caliper. And to go on about the booster being faulty makes me wonder about who they have working at that dealer.

slaviers said:
I figured the valve was bad or it had junk stuck it.

That's what it sounds like, and that's a problem I've seen after someone pushed the caliper piston back in during a brake job. If contaminated fluid gets pushed back through the abs module it can gum up the valves. At my work, when compressing the caliper pistons back in, it is mandatory that the caliper bleeder is cracked and the hose pinched so that the fluid can not go back up into the abs module. Not saying thats what happened here, there are other things that can go wrong with the module.

slaviers said:
Sorry for the rant.

Nothing to be sorry about. I know I wouldn't want a four figure estimate without a clear idea of what is being replaced and why.
 

slaviers

Original poster
Member
Jul 15, 2012
8
McGMT said:
IMHO it sounds like the ABS is doing it, the MC couldn't hang just one front caliper. If it was both then yea, but just one, no. And the fact that cracking it open after the abs controller released it shows even more.

When you change brakes is the one harder to push back in than the other?

Just givin my opinion, gotta run n don't have time to check the sheets...

POW! I just had a thought, it kind of hurt actually lol. Anyway, the ABS controller has a "Pre-Loader" that sets it up to take up the air-space between the pad and the rotor so when traction control, stability control and such is activated it can actually apply the brakes. Either way I think you have a wonky ABS block and they aren't going deep enough to identify the problem. What year is your vehicle, just would like to know so we know if it has stability or not.

Its a 2003 GMC Envoy SLE with 4.2 L6. I think maybe I should find a Power Motive pressure flusher and thoroughly flush the fluid all the way from reservoir to all four calipers. maybe this will hopefully get all the junk fluid out of the system.

When I get back to work I will check to see if I can find out if it has stability control. Any indications to look for to see if it hass stability/traction control
 

Denali n DOO

Member
May 22, 2012
5,596
slaviers said:
Its a 2003 GMC Envoy SLE with 4.2 L6. I think maybe I should find a Power Motive pressure flusher and thoroughly flush the fluid all the way from reservoir to all four calipers. maybe this will hopefully get all the junk fluid out of the system.

When I get back to work I will check to see if I can find out if it has stability control. Any indications to look for to see if it hass stability/traction control

The button on the shifter you press to turn off traction control, hold the button and it will turn off stabilitrak and indicate so on the dash. If you can't turn it off I guess you don't have it.
 

MAY03LT

Member
Nov 18, 2011
3,412
Delmarva
slaviers said:
I think maybe I should find a Power Motive pressure flusher and thoroughly flush the fluid all the way from reservoir to all four calipers. maybe this will hopefully get all the junk fluid out of the system.

I've yet to fix one by flushing. You might be the first, hope it works!:cool:
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
And to properly flush an ABS, you need the Tech2 to cycle it through the valves.
 

McGMT

Member
Jun 17, 2012
621
Don't believe there was stability before 06.....
 

Sparky

Member
Dec 4, 2011
12,927
Stabilitrak only existed on pre-05 or 06 (forget which) that were 2WD. 4WD trucks didn't get it until after that date.

I had some wear issues on my old car that kept grinding my driver front brake even after replacing a bunch of stuff also. Drove me nuts, figured it was the ABS block or something. Then I engaged the ABS one day in the rain when some idiot decided to try to get me to rear-end him in the middle of a busy highway :eek: :mad: Freakin moron. But after that I noticed the issues on that side went away. Triggering the ABS like that apparently fixed the problem.

So... maybe go find a slippery surface of some sort and smash the brakes hard to get the ABS to fire on that side. It might just clear up the issue. Worth a try anyway.
 

McGMT

Member
Jun 17, 2012
621
Sparky said:
Stabilitrak only existed on pre-05 or 06 (forget which) that were 2WD. 4WD trucks didn't get it until after that date.

I had some wear issues on my old car that kept grinding my driver front brake even after replacing a bunch of stuff also. Drove me nuts, figured it was the ABS block or something. Then I engaged the ABS one day in the rain when some idiot decided to try to get me to rear-end him in the middle of a busy highway :eek: :mad: Freakin moron. But after that I noticed the issues on that side went away. Triggering the ABS like that apparently fixed the problem.

So... maybe go find a slippery surface of some sort and smash the brakes hard to get the ABS to fire on that side. It might just clear up the issue. Worth a try anyway.

It musta been 06 that they started the stability on all because mine has it and its an 06 4x4
 

slaviers

Original poster
Member
Jul 15, 2012
8
have now replaced brake booster and master cylinder again. Flushed and replaced all the fluid. after a few miles of driving, bring it back to shop, jack up front end, try to turn wheels, then open bleeders. I now believe that both calipers are holding very slight pressure. It seems that no matter which bleeder I open, both wheels seem to get easier to turn. Opening line at master cylinder does not seem to help. Does the abs separate/isolate the front calipers? Looks like rock auto wants 350 for just the valve. looks hard to replace. If I change just the valve block, will I have to have dealer reprogram it? Do I need to replace motor and module? Any advice would be appreciated.
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
If you do replace the valve block, you will have to bring it to a dealer or shop with a Tech2 to properly bleed it. Some reprogramming may be required if you also replace the ABS module (the plastic brain on top of the valve).
 

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