Brake bleeding
#11
08-26-2012, 09:36 AM
If and when you do Monty please do a write up of everything that you've discovered. I'm very interested myself....I've also been looking through ebay and other sites, waiting for an aftermarket tool that has equivalent functions to the DRBIII, maybe a
Snapon Solus, or any brand that performs relative tasks to the dealer tool. So far I've found a few at roughly 1/4 the price of the DRB. Maybe someone here knows which brand is a good choice? pkucan's idea seems like it might work. If the air in the abs is pushed out of the CAB from repeated cycles why wouildn't we be able to bleed the entire system that way instead of the dealer nailing us for a couple hundred?
@pkucan...ARTILLARY !!!!! (I wore the Cross Cannon myself)
Snapon Solus, or any brand that performs relative tasks to the dealer tool. So far I've found a few at roughly 1/4 the price of the DRB. Maybe someone here knows which brand is a good choice? pkucan's idea seems like it might work. If the air in the abs is pushed out of the CAB from repeated cycles why wouildn't we be able to bleed the entire system that way instead of the dealer nailing us for a couple hundred?
@pkucan...ARTILLARY !!!!! (I wore the Cross Cannon myself)
#12
08-27-2012, 11:39 PM
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Awesome,I did a repair on one module but it was just an internal part swap,I haven't dug any deeper to learn more about the how's.....Everything I see and read from the shops that service ABS modules seem as though they have a modified harness and a computer with emulation and testing software...maybe you can figure out a simple way to cycle it? Very interested....
#13
09-12-2012, 01:48 PM
Here is what I have figured out so far:
There are 6 solenoids in the HCU. Three are isolation valves and three are dump valves. The solenoids are controlled internally by the CAB. There is no way to activate them via the wiring harness. However, if you remove the CAB from the HCU, you can clearly see six posts that fit inside the solenoid coils.These posts house the valve "stems". When voltage is applied to the coils, the "stems" are affected by the magnetic field produced by the coil, which opens or closes the valves. The solenoids are strictly on/off operated. I modified a shift solenoid from a transmission and placed it over one of the posts and jumped 12vdc to the coil. It didn't activate the valve. I suspect the coil I used is too weak. I am currently looking at a junk yard CAB that doesn't work, so I can rob the coils out of it. I can then make a harness for them, place them over the valve posts and activate them in pairs while jumping 12vdc to the pump.
In the meantime, I discovered my HCU is contaminated with a bunch of crap from sitting dry. The proportioning valve was severely corroded inside so I replaced it, but the HCU is going to have to wait until I can afford it. So, I bypassed the ABS for now, just to get it on the road. I have excellent brakes and no ABS or brake lights on. I'm going to try to get the ABS back online before the snow flies.
The original transmission problem turned out to be a bad transfer case. Everything has been repaired/replaced and the D was given a shiny new inspection sticker yesterday.
I'm not going to sit here and advocate bypassing the ABS. I have been without a DD since June and had to get a vehicle on the road. However, in a pinch, it is possible to do it, if you completely understand how brakes work.
As soon as I get another CAB and HCU I will experiment with the old units and post back the results.
There are 6 solenoids in the HCU. Three are isolation valves and three are dump valves. The solenoids are controlled internally by the CAB. There is no way to activate them via the wiring harness. However, if you remove the CAB from the HCU, you can clearly see six posts that fit inside the solenoid coils.These posts house the valve "stems". When voltage is applied to the coils, the "stems" are affected by the magnetic field produced by the coil, which opens or closes the valves. The solenoids are strictly on/off operated. I modified a shift solenoid from a transmission and placed it over one of the posts and jumped 12vdc to the coil. It didn't activate the valve. I suspect the coil I used is too weak. I am currently looking at a junk yard CAB that doesn't work, so I can rob the coils out of it. I can then make a harness for them, place them over the valve posts and activate them in pairs while jumping 12vdc to the pump.
In the meantime, I discovered my HCU is contaminated with a bunch of crap from sitting dry. The proportioning valve was severely corroded inside so I replaced it, but the HCU is going to have to wait until I can afford it. So, I bypassed the ABS for now, just to get it on the road. I have excellent brakes and no ABS or brake lights on. I'm going to try to get the ABS back online before the snow flies.
The original transmission problem turned out to be a bad transfer case. Everything has been repaired/replaced and the D was given a shiny new inspection sticker yesterday.
I'm not going to sit here and advocate bypassing the ABS. I have been without a DD since June and had to get a vehicle on the road. However, in a pinch, it is possible to do it, if you completely understand how brakes work.
As soon as I get another CAB and HCU I will experiment with the old units and post back the results.