[T-bucket23]

I have a 99 Silverado with a problem I have not seen before. The customer came in with a rotted brake line from the master to the ABS unit. It is the ABS unit that is under the middle of the truck (who thought this was a good idea).
One of the techs replaced the line and bled the brakes.
The left front caliper will not push any fluid out of the bleeder. We cracked the line where the hard line goes into the rubber flex hose and there is no fluid pressure there when you push the pedal and the pedal doesnt sink.

The pedal feels normal. All the lines going into the ABS unit are real crusty so I really dont want to attempt to remove them without good reason.
Has anyone seen an ABS unit keep fluid from flowing to one of the wheels.

Any insight would be appreciated.

Thanks

[LATECH]

I cant say to date that I have but would suspect that is whats happening.
I think that vehicle requires an "automated bleed" I could be wrong.
Kinda sounds like and isolation valve is stuck or plugged.
I saw a bulletin on GM abs and some abs systems self destruct with issues like line breakage, but I havent seen it on a chevy pickup. I had a saturn that did though.

Does it have any ABS codes?

[T-bucket23]

Originally Posted by latech

I cant say to date that I have but would suspect that is whats happening.
I think that vehicle requires an "automated bleed" I could be wrong.
Kinda sounds like and isolation valve is stuck or plugged.
I saw a bulletin on GM abs and some abs systems self destruct with issues like line breakage, but I havent seen it on a chevy pickup. I had a saturn that did though.

Does it have any ABS codes?

I have not been hands on yet unfortunately. It is a shop I work at part time and I was trying to give them some phone support. I could not find and special bleeding instructions for that system like some of the S10s and small blazers had. Some of them you need the scan tool or the special spoons to manipulate the valves. Neither All Data or Mitchel called out anything special.
its never good when a line breaks, all the crap that has been in the nooks and crannys of the system gets dislodged and ends up every where. I have seen a lot of ABS issues but not like this.
I am going to look at it tomorrow night if they dont get it fixed. i will let you know if I find anything

[LATECH]

I suspect the abs unit is the trouble, but its anybodys guess. I would like to know what it is when they find it.I may see something like it in the future, after all I live in the snow/salt/rust belt and theres lotsa chevy trucks around here.

[T-bucket23]

Got it fixed. It must have been a stuck valve in the ABS unit. I told them to take it out and do a couple panic stops to try to free the valve. After they did this they were able to bleed the bad wheel.

[LATECH]

Excellent thinking, induce an ABS stop.Makes perfect sense.Glad to hear it is good to go. I will definetly keep track of that info.

[joe_padavano]

I believe you are supposed to use a scan tool like a Tech II or a Genysis to actuate the ABS unit while bleding the brakes to get the trapped air out.

[arizray]

Did the rotted line possible get plugged by debris inside the line?

[T-bucket23]

Originally Posted by joe_padavano

I believe you are supposed to use a scan tool like a Tech II or a Genysis to actuate the ABS unit while bleding the brakes to get the trapped air out.

not needed on that vehicle to bleed, however it would have made it easy to cycle the individual valves and probably would have freed the stuck one. Unfortunately that shop has limited resources from the scan tool standpoint.