94 k1500 rwal failure hyd or elec ?

crabtruck · 07-09-2007, 03:33 PM

truck was parked in garage and almost never started for about six years.
brakes had not given any hint of problem before this from lite, leaks or
performance. Took 3 10 mile trips with 1200 lbs loads to dump, 1 a day,
and parked again for 2 days. Pulled truck out again to driveway and found
rr brake had leaked about 2-3 tablespoons so pulled wheel to look at it.
Shoes had worn enough that extended cylinder seal had failed. Replaced
shoes/springs/cylinder(bench bled) and did LR as good practice. LR was
due but not to gone status.

Attempted to bleed but had almost no output from either side even checking
at line-to-cylinder. Park/ABS lite on solid with eng on/off, pedal or no.
Lite brighter with park brake so that switch ok. Resevoir has never
been below 3/4 norm.

Have pulled 4wire to HPA/LPA with no change. Have
disconnected batt for day with no reset/change. Have checked fuses.
Pedal is always resonably firm about halfway down.

Does anyone have the proper elect/hyd diagrams for 94 k1500 rwal?
Advise on troubleshooting simplest foward? Thanks for anything ...

mrjohnwayne · 07-09-2007, 03:44 PM

did you adjust the rear brakes manually before bleeding. If they are not or barely coming into contact with the drum you will never build pressure.

crabtruck · 07-09-2007, 03:58 PM

thanks for reply john. yes to adjusting. I don't get more than a drip from the brake line itself when free from cylinder, gravity would give as much.
Pressure is not being sent to rear at all apparently. Like line was blocked.
No visible damage to anything front to rear, so I am looking for an internal
failure of something. Master/proportinal/rwal. Now thinking its not electrical
but would still like to go through wiring for it. Is the single wire on top of
proportioning a pull or twist off?

mudseeker · 07-09-2007, 05:16 PM

how are you bleeding your brakes? gravity, foot, vacum or pressure bleeder? some of these technuiqes require you to either push or pull out the valve stem on the combo valve to allow fluid to flow.

crabtruck · 07-09-2007, 05:47 PM

gravity gives 1 or 2 drips, using pedal doesn't change this. I don't have pressure or vacum setups to use. There may have been more fluid loss from rear lines than I realized even though the master is full. Could the stem on combo have moved by loss enough to get "stuck" to far in/out? How can I check its position? What's the right position?

mrjohnwayne · 07-09-2007, 05:58 PM

the valve should have a pull off wire connection. If the truck sat for that long could very well be a problem with the abs unit but I don't know.

mudseeker · 07-09-2007, 07:10 PM

do you have a spongy pedal when all the bleeders are closed? does it build pressure after pumping for a while? i'm thinking you have air in the ABS valves, if so you willl need a scan to bleed the ABS valves before you can bleed your base brake system.

crabtruck · 07-09-2007, 07:36 PM

I'm now thinking there may be air in the rwal valves since the truck had years to drbble from that line with the bad RR cylinder. The pedal is firm at about half way down, not spongy, but that maybe because it is support by the fronts. What is the scan proceedure? Thanks for responses.

mudseeker · 07-09-2007, 07:56 PM

the scan tool operates the valves from the DCL under the steering coloumn. it opens and closes the valves untill all the air is purged. unless you have a 3k dollar scan tool lying around it's best to take it to a shop. you say you don't have a spongy, so it could be a blocked or collasped line. i would check the rubber hose going from the frame to the axle.

crabtruck · 07-09-2007, 09:10 PM

I just got back from looking mudseeker, and as I suspected, no I do NOT have a 3k dollar scan tool lying around. Seriuosly however, I am quite good with jigging electronic systems. What I don't have is any idea what exactly I'm trying to accomplish. It seems that the valves should be able to be directly controllable by removing the wires at the valves and attaching my own. Do you have any wiring diagrams for a 94 k1500?

07-09-2007, 03:33 PM	#1
crabtruck Senior Member Join Date: Jul 2007 Location: on your 9 Posts: 3,364	94 k1500 rwal failure hyd or elec ? truck was parked in garage and almost never started for about six years. brakes had not given any hint of problem before this from lite, leaks or performance. Took 3 10 mile trips with 1200 lbs loads to dump, 1 a day, and parked again for 2 days. Pulled truck out again to driveway and found rr brake had leaked about 2-3 tablespoons so pulled wheel to look at it. Shoes had worn enough that extended cylinder seal had failed. Replaced shoes/springs/cylinder(bench bled) and did LR as good practice. LR was due but not to gone status. Attempted to bleed but had almost no output from either side even checking at line-to-cylinder. Park/ABS lite on solid with eng on/off, pedal or no. Lite brighter with park brake so that switch ok. Resevoir has never been below 3/4 norm. Have pulled 4wire to HPA/LPA with no change. Have disconnected batt for day with no reset/change. Have checked fuses. Pedal is always resonably firm about halfway down. Does anyone have the proper elect/hyd diagrams for 94 k1500 rwal? Advise on troubleshooting simplest foward? Thanks for anything ... Last edited by crabtruck; 07-29-2007 at 12:37 AM.

07-09-2007, 03:44 PM	#2
mrjohnwayne Senior Moderator Join Date: Apr 2005 Location: Texas Posts: 3,722	did you adjust the rear brakes manually before bleeding. If they are not or barely coming into contact with the drum you will never build pressure. __________________ John Wayne 2000 F-350 7.3L Powerstroke 4x4

07-09-2007, 05:16 PM	#4
mudseeker Senior Moderator Join Date: Feb 2006 Location: michigan Posts: 6,373	how are you bleeding your brakes? gravity, foot, vacum or pressure bleeder? some of these technuiqes require you to either push or pull out the valve stem on the combo valve to allow fluid to flow. __________________ i'd rather be hunting

07-09-2007, 05:58 PM	#6
mrjohnwayne Senior Moderator Join Date: Apr 2005 Location: Texas Posts: 3,722	the valve should have a pull off wire connection. If the truck sat for that long could very well be a problem with the abs unit but I don't know. __________________ John Wayne 2000 F-350 7.3L Powerstroke 4x4

07-09-2007, 07:10 PM	#7
mudseeker Senior Moderator Join Date: Feb 2006 Location: michigan Posts: 6,373	do you have a spongy pedal when all the bleeders are closed? does it build pressure after pumping for a while? i'm thinking you have air in the ABS valves, if so you willl need a scan to bleed the ABS valves before you can bleed your base brake system. __________________ i'd rather be hunting

07-09-2007, 03:58 PM	#3
crabtruck Senior Member Join Date: Jul 2007 Location: on your 9 Posts: 3,364	thanks for reply john. yes to adjusting. I don't get more than a drip from the brake line itself when free from cylinder, gravity would give as much. Pressure is not being sent to rear at all apparently. Like line was blocked. No visible damage to anything front to rear, so I am looking for an internal failure of something. Master/proportinal/rwal. Now thinking its not electrical but would still like to go through wiring for it. Is the single wire on top of proportioning a pull or twist off?

07-09-2007, 05:47 PM	#5
crabtruck Senior Member Join Date: Jul 2007 Location: on your 9 Posts: 3,364	gravity gives 1 or 2 drips, using pedal doesn't change this. I don't have pressure or vacum setups to use. There may have been more fluid loss from rear lines than I realized even though the master is full. Could the stem on combo have moved by loss enough to get "stuck" to far in/out? How can I check its position? What's the right position?

07-09-2007, 07:36 PM	#8
crabtruck Senior Member Join Date: Jul 2007 Location: on your 9 Posts: 3,364	I'm now thinking there may be air in the rwal valves since the truck had years to drbble from that line with the bad RR cylinder. The pedal is firm at about half way down, not spongy, but that maybe because it is support by the fronts. What is the scan proceedure? Thanks for responses. Last edited by crabtruck; 07-29-2007 at 12:39 AM.

07-09-2007, 07:56 PM	#9
mudseeker Senior Moderator Join Date: Feb 2006 Location: michigan Posts: 6,373	the scan tool operates the valves from the DCL under the steering coloumn. it opens and closes the valves untill all the air is purged. unless you have a 3k dollar scan tool lying around it's best to take it to a shop. you say you don't have a spongy, so it could be a blocked or collasped line. i would check the rubber hose going from the frame to the axle. __________________ i'd rather be hunting

07-09-2007, 09:10 PM	#10
crabtruck Senior Member Join Date: Jul 2007 Location: on your 9 Posts: 3,364	I just got back from looking mudseeker, and as I suspected, no I do NOT have a 3k dollar scan tool lying around. Seriuosly however, I am quite good with jigging electronic systems. What I don't have is any idea what exactly I'm trying to accomplish. It seems that the valves should be able to be directly controllable by removing the wires at the valves and attaching my own. Do you have any wiring diagrams for a 94 k1500? Last edited by crabtruck; 07-29-2007 at 12:40 AM.

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