ABS problems

Tiny
REDFURY
  • MEMBER
  • 1998 CHEVROLET ASTRO
  • V8
  • AUTOMATIC
  • 174,000 MILES
Engine idles fine, but RPMs rise significantly when put into FWD and Reverse ( automatic ). This is in a 1998 Astro with a V8 conversion. It was idling at 1200-1500rpm, but after replacing the TPS and resetting the IAC the idle speed is fine, just goes up when put into gear and over runs the ABS on slick roads! Not sure where to look.
Friday, January 14th, 2011 AT 1:25 PM

33 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,544 POSTS
We only deal with direct fit parts. It is hard to answer when we don't know what has been done as far as modifications.
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Tuesday, March 8th, 2011 AT 2:36 AM
Tiny
REDFURY
  • MEMBER
  • 8 POSTS
Yeah, it's a bit of a mess. I just converted the PCM to the express van PCM due to a lot of problems like I posted above. I've learned a lot about what was done wrong with the V8 was dropped into this van.

Hopefully I'll have it sorted out shortly. Lots of incompatibility between years such as the computer and the transmission that was in there, then the new computer doesn't like the old O2 sensors because of the way they are grounded. Not exactly something to tackle in a format like this one. I've got threads going on in multiple tuner sites, but I appreciate the response.
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Tuesday, March 8th, 2011 AT 3:12 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,544 POSTS
I can't believe they got it to fit. I see you have your hands full based on the picture.
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Tuesday, March 8th, 2011 AT 4:04 AM
Tiny
REDFURY
  • MEMBER
  • 8 POSTS
Actually, it fits in there pretty well!
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Tuesday, March 8th, 2011 AT 1:16 PM
Tiny
CHPHOTO1
  • MEMBER
  • 6 POSTS
  • 1997 CHEVROLET ASTRO
  • 6 CYL
  • AWD
  • AUTOMATIC
  • 110,000 MILES
My Astro's brakes have an odd, but intermittent problem. Occasionally when I try to stop, they will make a groaning sound and I can feel the pedal push back against my foot and the van doesn't want to stop. If I continue to push on the pedal, you can hear a thump and then the van will stop short. A couple of times when this has happened, the pedal went all the way to the floor, the brakes released and the van started forward more quickly as the idle speed kicked in. I've replaced the pads, rotors and calipers as well as bled the lines. Do I need a new master cylinder or sensors, or what?
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Wednesday, September 25th, 2019 AT 10:17 AM (Merged)
Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
This sounds like the ABS is kicking in because of a bad wheel speed sensor. This video will show you how to find out which sensor is bad.

https://youtu.be/rTtAnsOlZU4

Please run down this guide and report back.
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Wednesday, September 25th, 2019 AT 10:17 AM (Merged)
Tiny
CHPHOTO1
  • MEMBER
  • 6 POSTS
Ok, based on the reply, I suspect a faulty brake booster. I've looked over the diagram and pictures and feel pretty confident about replacing it. I've priced Astro brake boosters online and they're about $275. Is there a way I can test the one I have and make sure that's what I need before I put out the cash?
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Wednesday, September 25th, 2019 AT 10:17 AM (Merged)
Tiny
BLUELIGHTNIN6
  • MECHANIC
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The booster is hydraulic so the test is difficult. Did you try the scan?
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Wednesday, September 25th, 2019 AT 10:17 AM (Merged)
Tiny
CHPHOTO1
  • MEMBER
  • 6 POSTS
I put on the new booster, and the power steering works better than it has since I bought the van, but now the brake pedal goes all th way to the floor and won't come back up.
I had to take out the master cylinder to get the old booster out and the new one in, so I assume the lines need bled, which I'm going to do in the morning, but the pedal to the floor and not coming up concerns me. Is there anything else I should be looking at?
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Wednesday, September 25th, 2019 AT 10:17 AM (Merged)
Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
You most likely just need to bleed the hydro-boost system since the brake booster was replaced. After bleeding the hyrdo-boost system, also bleed the brake system as you normally would at each wheel. Follow the steps below to bleed the boost system, let me know how it goes afterwards..


https://www.2carpros.com/forum/automotive_pictures/261618_Noname_708.jpg

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Wednesday, September 25th, 2019 AT 10:17 AM (Merged)
Tiny
CHPHOTO1
  • MEMBER
  • 6 POSTS
I tried bleeding the booster and the brake lines (used your instructions and instructions in Chilton manual) and I have the same problem. Did I get a bad booster?
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Wednesday, September 25th, 2019 AT 10:17 AM (Merged)
Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
That is possible, or you may have accidentally left something loose such as a vacuum line somewhere or something.
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Wednesday, September 25th, 2019 AT 10:17 AM (Merged)
Tiny
CHPHOTO1
  • MEMBER
  • 6 POSTS
Took the new boost off and put the old one back on and the pedal is acting normally again. The groaning problem is still there, so it's back to the store for a little exchange action. Thanks again for all your help.
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Wednesday, September 25th, 2019 AT 10:17 AM (Merged)
Tiny
CHPHOTO1
  • MEMBER
  • 6 POSTS
I finally got the scanner and found the right front wheel speed sensor was out got a new one for $89.00 all fixed! I love this site.
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Wednesday, September 25th, 2019 AT 10:17 AM (Merged)
Tiny
DOOBY1964
  • MEMBER
  • 6 POSTS
  • 1998 CHEVROLET ASTRO
  • 6 CYL
  • AWD
  • AUTOMATIC
  • 48,000 MILES
Why does my ABS keep slipping when I apply the brakes? The ABS light does not come on.
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Wednesday, September 25th, 2019 AT 11:18 AM (Merged)
Tiny
RHALL77
  • MECHANIC
  • 3,361 POSTS
What do you mean by slipping. If they are activating, you might have rust build up on the front sensors. I would suggest cleaning the mating surface for the sensor, clean the sensor then road test.
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Wednesday, September 25th, 2019 AT 11:18 AM (Merged)
Tiny
DOOBY1964
  • MEMBER
  • 6 POSTS
What I mean is that when I apply the brakes it doesn't come to a complete stop. Instead the car still will roll. If you stop far enough in advance then you can pump the brakes a couple of times and then It will stop.
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Wednesday, September 25th, 2019 AT 11:18 AM (Merged)
Tiny
RHALL77
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Does the brake pedal go to the floor
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Wednesday, September 25th, 2019 AT 11:18 AM (Merged)
Tiny
DOOBY1964
  • MEMBER
  • 6 POSTS
No, the brakes were checked and said that there was still a few months worth of pad left. They mentioned about taking the rotor apart and checking the gear
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Wednesday, September 25th, 2019 AT 11:18 AM (Merged)
Tiny
RHALL77
  • MECHANIC
  • 3,361 POSTS
When they check the gear, tell them to check the abs sensor for rust build up on the surface area where it mounts
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Wednesday, September 25th, 2019 AT 11:18 AM (Merged)

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