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03 astro van intermittent low pedal


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meev182
Novice

Jun 14, 2012, 1:12 PM

Post #1 of 13 (3677 views)
03 astro van intermittent low pedal Sign In

2003 chevy astro van
4.3l v6 2wd
4 wheel disc brakes w/ hydroboost

rr wheel seal was leaking so i changed rear wheel seals, serviced the rear end, and replaced all the pads and rotors.

i have an intermittent low pedal before and after service. low pedal only happens when vehicle is not running. goes to the floor for one or two pumps, then its fine. no issues with braking while driving. no brake light on in the instrument cluster.

it always acts up if i pump the brake pedal hard with vehicle running then i turn it off. hte first pump or two always go to the floor. if i do that, turn it off, dont touch the brake pedal, then start it, pedal is fine.

any ideas? ebcm? master cylinder? i dont think its the hydroboost...this is not normal for a hydroboost set up, correct?

thanks in advance for your help :o)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jun 14, 2012, 1:13 PM

Post #2 of 13 (3671 views)
Re: 03 astro van intermittent low pedal Sign In


Quote
any ideas? ebcm? master cylinder? i dont think its the hydroboost...this is not normal for a hydroboost set up, correct?


How about something done wrong in the brake job?



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



meev182
Novice

Jun 14, 2012, 1:21 PM

Post #3 of 13 (3664 views)
Re: 03 astro van intermittent low pedal Sign In

problem existed before and after. all slides and pins were cleaned and all calipers retracted fine. i pinched off all the hoses and the problem still exists. i also bled the brakes to make sure there wasnt air in the system.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jun 14, 2012, 1:24 PM

Post #4 of 13 (3656 views)
Re: 03 astro van intermittent low pedal Sign In

If you pinched off all 4 wheels and still can't get a pedal, replace the master.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



meev182
Novice

Jun 14, 2012, 1:41 PM

Post #5 of 13 (3642 views)
Re: 03 astro van intermittent low pedal Sign In


In Reply To
If you pinched off all 4 wheels and still can't get a pedal, replace the master.


wouldnt a master cylinder show its self at all times? like i said, it only does it intermittently with the car off...pedal is fine while driving at all times.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Jun 14, 2012, 5:37 PM

Post #6 of 13 (3589 views)
Re: 03 astro van intermittent low pedal Sign In

All times - NO,

T



Discretesignals
Ultimate Carjunky / Moderator
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Jun 14, 2012, 6:05 PM

Post #7 of 13 (3583 views)
Re: 03 astro van intermittent low pedal Sign In


Quote
i have an intermittent low pedal before and after service. low pedal only happens when vehicle is not running. goes to the floor for one or two pumps


This appears to be normal operation of a vacuum brake booster. Your pedal is going to go down a couple pumps before you exhaust the vacuum from the booster with the engine not running.





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Hammer Time
Ultimate Carjunky / Moderator
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Jun 14, 2012, 6:42 PM

Post #8 of 13 (3574 views)
Re: 03 astro van intermittent low pedal Sign In


Quote
This appears to be normal operation of a vacuum brake booster.


Yeah it would be. Problem is that this is not vacuum boost. It's hydroboost.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Jun 14, 2012, 6:47 PM

Post #9 of 13 (3568 views)
Re: 03 astro van intermittent low pedal Sign In

I can't remember if hydroboost does the same thing. It does have an accumulator.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jun 14, 2012, 6:58 PM

Post #10 of 13 (3562 views)
Re: 03 astro van intermittent low pedal Sign In

Hydroboost actually acts the way his is, just the opposite of vacuum. Vacuum boost drops the pedal when activated, hydroboost lifts the pedal when activated so he may not have a problem at all.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Sidom
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Jun 15, 2012, 12:31 AM

Post #11 of 13 (3539 views)
Re: 03 astro van intermittent low pedal Sign In

I think you're right D....On a hydro-boost system when you press on the pedal & it will go all the way to the floor and then the pedal will "bounce" while your holding it down.

If the pedal is going to the floor with very little pressure & doesn't bounce it may be a bypassing master cylinder.
If the op retracted the pistons without opening the bleeders it's possible he trashed his master.....

If the van is new to him, then he probably isn't use to the system.....If he's had the van for a while a now it "seems different" I would be tempted to put a master on it....


meev182
Novice

Jun 16, 2012, 8:18 AM

Post #12 of 13 (3486 views)
Re: 03 astro van intermittent low pedal Sign In


In Reply To
If the pedal is going to the floor with very little pressure & doesn't bounce it may be a bypassing master cylinder.
If the op retracted the pistons without opening the bleeders it's possible he trashed his master.....

If the van is new to him, then he probably isn't use to the system.....If he's had the van for a while a now it "seems different" I would be tempted to put a master on it....


i didnt open the bleeders but i've done hundreds of brake jobs without opening the bleeders...never once had a problem doing it that way. the van is not mine, but the pedal was the same before and after (except the fact it stops better and the pedal is a little higher because of the new brake pads). as of now im going to leave it how it is...truck stops fine. very weird though!

In Reply To


Sidom
Veteran / Moderator
Sidom profile image

Jun 16, 2012, 8:42 AM

Post #13 of 13 (3484 views)
Re: 03 astro van intermittent low pedal Sign In

Glad to hear everything is working good for you... Since the van isn't yours, this makes sense. If you haven't done too many of these units its a common mistake since on a normal hydro-boost system you can get the pedal to go all the way to the floor with a little force



In Reply To
i didnt open the bleeders but i've done hundreds of brake jobs without opening the bleeders...never once had a problem doing it that way.

On stuff like this you aren't going to get a problem everytime. If people did then no one would be doing it. The problem is, is that it only takes once to take out a master or ABS hydraulic unit. When you retract the piston without opening a bleeder, you are forcing fluid backwards thru systems that weren't designed to have fluid flow in that directions. Plus if you have ever looked at the condition of the fluid that is in the caliper, that would be another good reason to open a bleeder, it's dirty and black from all the heat and you are pushing that fluid back into the system. It's better to remove it and replace it with clean fluid. Not to mention it also makes it easier to retract the piston. It's kinda the same as when a guy says that he likes to pull a battery cable to check the alternator with the car running. He's not going to have a problem everytime but alls its takes is one surge to wipe out some expensive modules.... But it sounds like all is good and you are thorough enough to check your work & not let a problem go and that is a very good thing... Have a good weekend...






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