88 1500 spongy brakes and no "brake light" in-dash

[gen0]

I have an 88 c1500 4.3l v6 2wd w/ a 5spd standard and RWAL brakes

I have replaced the shoes/pads, new calipers, new wheel cylinders, new springs and self-adjusters, new drums and resurfaced rotors. I've also replaced the master cylinder (Hand bled before installing) and replaced the EBCM (Checked the resistance from pins A-D (4.06 ohms) and pins B-D (1.30 ohms) and cycled the key before plugging in the new one.

I have also cleaned the connections for the parking brake switch and the low level brake switch as well. I also bled the brakes throughly after replacing all these components.

My brakes were still spongy after all this, so I was going to run a diagnostic on the RWAL. However the dash brake light didnt energize so I pulled out the instrument cluster and checked for bad bulbs. I replaced it with a good one, and still no light.

At this point, the only components I haven't replaced are the proportioning valve and the control valve (for the rear brakes).
The parking brake works perfectly, but no brake light comes on when it is engaged.

I disconnected the rear brake line from the master cylinder and plugged it with a plastic fitting. The brakes instantly "pumped up"

here is my dilemma:
1 - in-dash brake light doesn't energize (even with a ground jumpered to the parking brake switch)
2 - the brakes are still spongy when the rear brakes are connected (after bleeding)

any ideas would be very much appreciated.

[quaddriver]

Originally Posted by gen0

I have an 88 c1500 4.3l v6 2wd w/ a 5spd standard and RWAL brakes

I have replaced the shoes/pads, new calipers, new wheel cylinders, new springs and self-adjusters, new drums and resurfaced rotors. I've also replaced the master cylinder (Hand bled before installing) and replaced the EBCM (Checked the resistance from pins A-D (4.06 ohms) and pins B-D (1.30 ohms) and cycled the key before plugging in the new one.

I have also cleaned the connections for the parking brake switch and the low level brake switch as well. I also bled the brakes throughly after replacing all these components.

My brakes were still spongy after all this, so I was going to run a diagnostic on the RWAL. However the dash brake light didnt energize so I pulled out the instrument cluster and checked for bad bulbs. I replaced it with a good one, and still no light.

At this point, the only components I haven't replaced are the proportioning valve and the control valve (for the rear brakes).
The parking brake works perfectly, but no brake light comes on when it is engaged.

I disconnected the rear brake line from the master cylinder and plugged it with a plastic fitting. The brakes instantly "pumped up"

here is my dilemma:
1 - in-dash brake light doesn't energize (even with a ground jumpered to the parking brake switch)
2 - the brakes are still spongy when the rear brakes are connected (after bleeding)

any ideas would be very much appreciated.

bleed the rwal. common problem, use a scan tool to cycle the pump while bleeding

[gen0]

I'm not too sure I'm clear about the process involved in doing that. The Chilton's I have on my truck isn't very clear about it.

On my truck, the rear wheel brake line leaves the master cylinder, goes through the proportioning valve then through the control valve, then out to the wheels. I understand how the ABS works, but I see no wires going to the control valve for the 2 solenoids. Am I missing a component here, or is the pump a seperate component than the control valve I'm speaking of? The control valve I mentioned is located directly beneath the master cylinder and is mounted to a bracket attached to the power booster (although nothing internal connects to the booster). There is a bleeder valve on the top. I have bled it before, but saw no air whatsoever. Is this what you meant by cycling the pump with a scan tool?

Also, could I cycle the pump using a jumper wire rather than the tool itself, or is the scanner necessary?

If the scan tool is necessary, will it work if the in-dash brake light doesn't work?

[quaddriver]

Originally Posted by gen0

I'm not too sure I'm clear about the process involved in doing that. The Chilton's I have on my truck isn't very clear about it.

On my truck, the rear wheel brake line leaves the master cylinder, goes through the proportioning valve then through the control valve, then out to the wheels. I understand how the ABS works, but I see no wires going to the control valve for the 2 solenoids. Am I missing a component here, or is the pump a seperate component than the control valve I'm speaking of? The control valve I mentioned is located directly beneath the master cylinder and is mounted to a bracket attached to the power booster (although nothing internal connects to the booster). There is a bleeder valve on the top. I have bled it before, but saw no air whatsoever. Is this what you meant by cycling the pump with a scan tool?

Also, could I cycle the pump using a jumper wire rather than the tool itself, or is the scanner necessary?

If the scan tool is necessary, will it work if the in-dash brake light doesn't work?

yes the solenoids are the 'pumps', what a brake friendly scan tool will do is hold both solenoids open so that the true braking function will be there and it then cycles them to get any bubbles out of the chambers. what I have found with the kelsey hayes rwal/4wal units is that if you change something 'back' towards the wheel cylinders, air bubbles can travel up the line to the unit and wont bleed at the master cyl bleed screws.

[gen0]

ok I'll give it a try.
Thanks for the advice

[gen0]

Ok I gave it a shot. I bled the rear wheels first (passenger side then driver side). Then I bled the RWAL valve. They don't sell a scan tool at any of my automotive shops locally, so I couldn't cycle the solenoids in the RWAL. I did however go and drive the truck after bleeding it, and used the brakes really hard to cause the RWAL to kick in to actuate them, and then re-bled it. Still no luck. Spongy as ever.

I still get no in-dash brake light either even with the new EBCM...not even a diagnostic flash at start-up. I rechecked the bulb and even pulled it out and put 12v to it..lit right up.

where could I get a scan tool that can cycle the pumps? All I see locally are OBD II and code readers.
My truck is an OBD I.

Also do you know where I can get an ABS electrical schematic? The chilton's I have doesn't even show the EBCM in the schematics.

[quaddriver]

Originally Posted by gen0

Ok I gave it a shot. I bled the rear wheels first (passenger side then driver side). Then I bled the RWAL valve. They don't sell a scan tool at any of my automotive shops locally, so I couldn't cycle the solenoids in the RWAL. I did however go and drive the truck after bleeding it, and used the brakes really hard to cause the RWAL to kick in to actuate them, and then re-bled it. Still no luck. Spongy as ever.

I still get no in-dash brake light either even with the new EBCM...not even a diagnostic flash at start-up. I rechecked the bulb and even pulled it out and put 12v to it..lit right up.

where could I get a scan tool that can cycle the pumps? All I see locally are OBD II and code readers.
My truck is an OBD I.

Also do you know where I can get an ABS electrical schematic? The chilton's I have doesn't even show the EBCM in the schematics.

well you needa snap on 2500 or better or modis or the GM star. the KH systems dont publish the internals outside of a dealership...you can get codes and stepguides in a service manual but not wiring.

[gen0]

alright, I'll check with a dealership tomorrow. Thanks for the input again.

[gen0]

ok I found quite a bit about RWAL brakes here
http://www.raybestos.com/OnLineTraining/

there's descriptions of delco morain ABS, kelsey hayes 2wd and 4wd ABS