K2500 Brake issues

[j cAT]

Originally Posted by ricnor

It's been a while since I last posted anything but I finally got a new master cylinder on the truck and a new set of front pads, replaced the metal brake lines on the rear axle and a section of the front to back line as it was very corroded, bled the system with new fluid. The rear shoes look fine and not worn too much at the tops so the drums would appear to be reasonably ok.
The truck at slow speeds seemed to stop fine BUT I went to take it for a short drive to bed in the pads a little and the feel of the brakes became worse and it's now not good.
I also noticed that the brake warning light which comes on at start up does not now go out.
I removed a small wire connector that goes to the pipe side of the ABS unit and the light comes on when the key is turned to start and then goes off after a few seconds, put the connector back on and the light stays on. Is the ABS unit knackard? could this be why the brakes still feel so bad? Is there a special method for ensuring no air is trapped in the ABS unit. I have bled the brakes three times now with no air coming out at any point and the fluid is clear. The front calipers are free to move and do not bind and the parking brake works great. Starting to loose the will to continue, might pull the engine and scrap the truck if I can't sort it soon.

with what occurred after your work I believe you have a leak. the red light is an indicator of this and then the braking effort getting worse.


the abs valve unit could have air in it but you must first repair all leaks. then at a GM dealership or repair shop with a brake bleeding machine that bleeds the brakes as the ABS unit is activated. this would be good to do to flush out all the old contaminated fluid anyway.

[jdmccright]

Not that I would really condone this but after I finished replacing the rear line, I had the ABS light on and had to cycle the valves to purge the air. I did that just by filling the reservoir to the top and driving around the neighborhood slowly, then repeatedly hitting the brakes hard to cause the ABS to cycle. After that I bled the brakes to remove any trapped air that got pushed down through the lines and topped off the reservoir. Not the safest thing to do, but it worked...do so at your own risk...you've been warned.

[ricnor]

As always thank you all for your replies.

I doubt I will be able to get my hands on a Bi-directional scanner for the truck unless it is a standard item that the european cars also use as my local GM dealer only does the rebadged daewoo cars, my nearest proper dealer is a few hundred miles away, there may well be a specialist garage closer but I haven't looked into this yet. All the parts I get are from specialists either from the USA if they will ship to europe or specialist parts people over here who then usually order it for me and I have to wait.

I'm going to have a look at all the joints on the braking system to see if there are any leaks and then try power bleeding the system again, after that I will give the stomping on the brakes ago (no issues as we live down a track that only we use so if it fails I'll just end up in field so no problems).

I will keep you posted.

[j cAT]

Originally Posted by ricnor

As always thank you all for your replies.

I doubt I will be able to get my hands on a Bi-directional scanner for the truck unless it is a standard item that the european cars also use as my local GM dealer only does the rebadged daewoo cars, my nearest proper dealer is a few hundred miles away, there may well be a specialist garage closer but I haven't looked into this yet. All the parts I get are from specialists either from the USA if they will ship to europe or specialist parts people over here who then usually order it for me and I have to wait.

I'm going to have a look at all the joints on the braking system to see if there are any leaks and then try power bleeding the system again, after that I will give the stomping on the brakes ago (no issues as we live down a track that only we use so if it fails I'll just end up in field so no problems).

I will keep you posted.

you can get the ABS going with a wet road and also a unpaved road. the abs should come on easy. this method does work sometimes . I would say that your work caused air to enter the ABS valve body and any air in the system is not going to create a good brake effort or an even brake effort.

wipe all the fittings you worked with mineral spirits and work the brakes to create pressure then see if there is leakage. use a cloth as the fluid is clear and does evaporate. small leaks are hard to find...look at the complete brake system. hoses and the rear brake cylinders.

[ricnor]

Just thought I would update everyone, the brakes still don't fill me with any confidence but they do now work as before and the lights have now gone out. There was a leak at the rear of the vehicle system that only became evident when large pressure was given to the brake pedal. At exactly the same point as this leak I also found a fuel leak and have had to replace the flow and return pipes. All good now, will just have to live with the brake feel as I have done for 7 years or so anyway.
I do have another issue which I will post elsewhere.
Thanks to all.