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 Post subject: No Power brakes full wheel lock
PostPosted: Sat Jul 02, 2011 1:51 pm 
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On my 97 at full left or right wheel lock i hear a nasty hissing and lose power brakes the brake pedal will sink almost to the ground before they stop the van. It makes the same sound when the van is not moving and i try to turn the wheels from side to side. I've checked the fluids and they are all good well my power steering fluid is actually a little high it was empty however when i got the van. any ideas? the only thing i can think of is the PS pump

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1998 GMC Safari AWD, BFGoodrich AllTerrain T/A
Jet performance tuner 91 octane preset, Jet under-drive pulleys
Rancho 999000 series shock, on-board controller to be installed later
DHC rock rails and skid plate Add-A-Leaf
G3500 front calipers
Zexel Torsen Diff
11" drums
180 amp Alternator
Long tru-cool 4590 trans cooler

1997 in storage (project coming soon)
1992 Chevy Astro "Z" vin (engine/trans in storage body crushed)
1995 Chevy Astro need lots of help project vehicle


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 Post subject: Re: No Power brakes full wheel lock
PostPosted: Sat Jul 02, 2011 2:02 pm 
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Sounds like your PS Pump is in need of replacement.

Buy a new unit, not a rebuilt.

Jim


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 Post subject: Re: No Power brakes full wheel lock
PostPosted: Sat Jul 02, 2011 2:21 pm 
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Are you referring to the '97 w/ 3500 calipers???

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'97 Safari, 280,000 miles,,, still kicking!
'93 Safari shorty, 350 swap


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 Post subject: Re: No Power brakes full wheel lock
PostPosted: Sat Jul 02, 2011 2:22 pm 
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yup

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1998 GMC Safari AWD, BFGoodrich AllTerrain T/A
Jet performance tuner 91 octane preset, Jet under-drive pulleys
Rancho 999000 series shock, on-board controller to be installed later
DHC rock rails and skid plate Add-A-Leaf
G3500 front calipers
Zexel Torsen Diff
11" drums
180 amp Alternator
Long tru-cool 4590 trans cooler

1997 in storage (project coming soon)
1992 Chevy Astro "Z" vin (engine/trans in storage body crushed)
1995 Chevy Astro need lots of help project vehicle


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 Post subject: Re: No Power brakes full wheel lock
PostPosted: Sat Jul 02, 2011 2:54 pm 
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I just did this caliper swap on mine, 3" cylinder needs alot of fluid. I posted a thread on the other site
http://www.astrosafari.com/viewtopic.php?f=45&t=12087
and had to make a few mods. Are your calipers meant for a thicker rotor like the ones I got? Maybe shims would help.

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'97 Safari, 280,000 miles,,, still kicking!
'93 Safari shorty, 350 swap


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 Post subject: Re: No Power brakes full wheel lock
PostPosted: Sat Jul 02, 2011 3:16 pm 
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the brakes work perfectly except for that one condition, i'm not sure the thickness of the 3500 rotors but i guess it wouldn't be hard to find out give me a minute to measure

edit:
stock 1997 rwd 1.04 inches thick
stock 1996 SRW G3500 1.53 inches thick

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1998 GMC Safari AWD, BFGoodrich AllTerrain T/A
Jet performance tuner 91 octane preset, Jet under-drive pulleys
Rancho 999000 series shock, on-board controller to be installed later
DHC rock rails and skid plate Add-A-Leaf
G3500 front calipers
Zexel Torsen Diff
11" drums
180 amp Alternator
Long tru-cool 4590 trans cooler

1997 in storage (project coming soon)
1992 Chevy Astro "Z" vin (engine/trans in storage body crushed)
1995 Chevy Astro need lots of help project vehicle


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 Post subject: Re: No Power brakes full wheel lock
PostPosted: Sat Jul 02, 2011 4:21 pm 
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Yeah, 1/2". I have 1/4" of shim in there and I'm thinking to add another 1/8" when I next get the ambition to tear into it.
I don't know if that has any relation to your issue but it may. My PS pump has had issues for some time before I did the big caliper but I have seen no change yet. (whines occasionally when turning hard at low speed)

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'97 Safari, 280,000 miles,,, still kicking!
'93 Safari shorty, 350 swap


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 Post subject: Re: No Power brakes full wheel lock
PostPosted: Sat Jul 02, 2011 4:48 pm 
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no matter what van i've driven they all whined a little bit at full wheel lock but mine i loud.if i can find my vacuum pump I'm going to try a couple things to see if air is trapped in there somewhere. 1/2 inch is a fair difference but nothing that i think the calipers stroke can't cover

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1998 GMC Safari AWD, BFGoodrich AllTerrain T/A
Jet performance tuner 91 octane preset, Jet under-drive pulleys
Rancho 999000 series shock, on-board controller to be installed later
DHC rock rails and skid plate Add-A-Leaf
G3500 front calipers
Zexel Torsen Diff
11" drums
180 amp Alternator
Long tru-cool 4590 trans cooler

1997 in storage (project coming soon)
1992 Chevy Astro "Z" vin (engine/trans in storage body crushed)
1995 Chevy Astro need lots of help project vehicle


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 Post subject: Re: No Power brakes full wheel lock
PostPosted: Sat Jul 02, 2011 4:52 pm 
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What is the life expectancy of the PS Pump?

How often have you flushed the PS Pumps fluid?

Thanks, Jim


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 Post subject: Re: No Power brakes full wheel lock
PostPosted: Sat Jul 02, 2011 5:29 pm 
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astroturf wrote:
What is the life expectancy of the PS Pump?

How often have you flushed the PS Pumps fluid?

Thanks, Jim


I never flushed but have replaced the steering box so I did drain and refill. I don't know of a way to flush per se but I think what I did would qualify.

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'97 Safari, 280,000 miles,,, still kicking!
'93 Safari shorty, 350 swap


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 Post subject: Re: No Power brakes full wheel lock
PostPosted: Sat Jul 02, 2011 5:53 pm 
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Vans pretty new to me so i haven't changed any of the fluids yet only topped off so it would pass the testing. Who knows when the last oil change was let alone power steering fluid

_________________
1998 GMC Safari AWD, BFGoodrich AllTerrain T/A
Jet performance tuner 91 octane preset, Jet under-drive pulleys
Rancho 999000 series shock, on-board controller to be installed later
DHC rock rails and skid plate Add-A-Leaf
G3500 front calipers
Zexel Torsen Diff
11" drums
180 amp Alternator
Long tru-cool 4590 trans cooler

1997 in storage (project coming soon)
1992 Chevy Astro "Z" vin (engine/trans in storage body crushed)
1995 Chevy Astro need lots of help project vehicle


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 Profile  
 
 Post subject: Re: No Power brakes full wheel lock
PostPosted: Fri Jul 13, 2012 4:49 am 
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My bet is on the bypass in the gear being messed up honestly. There's probably a pressure regulator for it that's stuck open. Strictly a guess however.


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