1999 Chevy Astro Unstable when Driving (ABS Pump Suspect?)

261 Views 8 Replies 5 Participants Last post by Mmusicman, 9 d ago

Lemansky22

Discussion Starter · 12 d ago

Short Read: ABS pump is faulty, and when turning the wheels seem to lock up. When turned all the way and I give it gas, it DOESN'T move! Also the van seems unstable when driving, mechanic checked out everything, Only ABS pump seems to be bad.

Repair Background:
Last week it visited the mechanic 5+ times because of a stalling issue. This was done In order starting from fuel pump. It kept on stalling until the crankshaft position sensor was replaced and now it's good. Mechanic changed:
1) Fuel Pump
2) Ignition Module and Ignition Coil
3) Distributor and Cap
4) Crankshaft Position Sensor

Current Problems:
1) Car is shaking at idle but engine mounts are new. It shakes when I rev it and turn the steering wheel.
2) Brakes are sinking to the floor, I took it to the mechanic today and he replaced Master Cylinder and tested for bubbles or air in system.

ABS pump module seems to be faulty. I went to the junkyard and scored a used ABS Pump for $55. The Repair should be $175 (Good deal?)

The question: When I give it gas, the van doesn't move. When wheels are pointed straight, it moves, but not when the wheels are turned. It seems to lock up. There is alot of resistance when turning the wheel by hand (On Jack). Has anyone experienced this? The van also seems unstable even on a straight drive, the car has a mind of its own.

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MechBob

· #2 · 11 d ago

Year?
AWD?

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ehbrown1

· #3 · 11 d ago

I have never ever seen nor heard of a faulty ABS pump causing steering problems.
Certainly not binding the drive train. Not possible.
Seems more than likely you are having an issue with the power steering/hydroboost system.
If the brake pedal goes to the floor and steering is difficult, that points you in that direction first.
Mechanic seems to be replacing itens at will without knowing what the actual problem is.

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Mmusicman

· #4 · 11 d ago

Sounds like the VERY COMMON AWD turning lockup issue
My 2000 AWD did that too

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Lemansky22

Discussion Starter · #5 · 11 d ago

MechBob said:
Year?
AWD?

It's a 1999 Astro RWD Hi-Top Mark 3 with 210k Miles.

Mmusicman said:
Sounds like the VERY COMMON AWD turning lockup issue
My 2000 AWD did that too

Can I ask you, what did it feel like? Right now I feel like my steering wheel and brakes have LIFE. Because when I move my steering wheel it pumps the brakes without me touching the brakes. Feels alive. Did your van feel unstable too?

ehbrown1 said:
I have never ever seen nor heard of a faulty ABS pump causing steering problems.
Certainly not binding the drive train. Not possible.
Seems more than likely you are having an issue with the power steering/hydroboost system.
If the brake pedal goes to the floor and steering is difficult, that points you in that direction first.
Mechanic seems to be replacing itens at will without knowing what the actual problem is.

Brake pedal does sink to the floor slowly, and when I turn my steering wheel the brakes go up and down. I think the van being unstable is more what I feel in my head, because I'm not used to driving like this. It just feels off. I drove on highways this morning perfectly fine, but in the back of my head there is still something that makes me think my van didn't operate the way it normally does. ABS lockup may cause this uneven ride? if I press the brakes the van starts limping (very small can't even tell) and it's just such a weird feeling!

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Mmusicman

· #6 · 11 d ago

Brakes AND steering are BOTH "power assist" which comes from hydraulic pressure sent by the power steering pump. If the pressure is low (low rpms, idle, or issue with pressure valve) then either can be affected.

It is actually common and normal at idle when turning hard to put an extra load on the power system... and can be felt in each since they "share" hydraulic pressure. Give it a little throttle and the problem usually corrects itself.

But if your PS pump is getting weak.. then problems may develop.

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AstroWill

· #7 · 10 d ago

Lemansky22 said:
Repair Background:
Last week it visited the mechanic 5+ times because of a stalling issue. This was done In order starting from fuel pump. It kept on stalling until the crankshaft position sensor was replaced and now it's good. Mechanic changed:
1) Fuel Pump
2) Ignition Module and Ignition Coil
3) Distributor and Cap
4) Crankshaft Position Sensor

All of those are testable, sounds like you need to find a new 'mechanic'.

The ABS system doesn't apply the brakes for you. I would really start with the power steering pump first. Not sure what all of your descriptions mean, what is limping?

Another thing you can do is pull the fuse for the ABS module, that will completely disable the ABS, see what symptoms still exists after doing that.

It's extremely helpful if your Year/Make/Model/Engine/AWD/Conversion/Mods/etc are listed in your signature and/or under your avatar so we know what we are working with both now and in the future. https://www.astrosafari.com/account/signature

van_details.jpg

AstroWill
1 mo ago

Under account details: https://www.astrosafari.com/account/account-details

account_details.jpg

AstroWill
1 mo ago

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MechBob

· #8 · 9 d ago

If you have any doubts about the ABS, simply pull the main fuse, or unplug the motor unit, and road test.

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Mmusicman

· #9 · 9 d ago

Apparently ABS units have their own bleeding process (I've never had to do it).
Pulling fuse might disable unit, but won't solve air in ABS system if there's a bleeding issue.

Mine also had an unrelated serious bad interaction with low pressure (and pedal to the floor) from bad PS pump (sticking pressure valve).

It should be near impossible for pedal to go to the floor.. even without power assist.
The only time mine has ever gone to the floor is when an ABS unit was activated.
Personally, I think the issues (at least in my case) were related.

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