Rear disc.......again Little Shop manufaturing kit questions

[Knuckle Dragger]

Thank you
It’ll do

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I wish I had your skills. 30+ years as a mechanic but no real fab experience.

 

[qwikgta]

i bought the kit a few weeks ago. Installed them in about 3-4 hours. It was easy. Only issue I have now is that I can't get the air out of the lines. I installed a new MC, front rotor/calipers, steal braided lines and new barking brake cables. No amount of bleeding has worked on getting the air out. Not that it has anything to do with the kit, but it sucks that I can't drive my truck.

 

[GarrettGmc]

i bought the kit a few weeks ago. Installed them in about 3-4 hours. It was easy. Only issue I have now is that I can't get the air out of the lines. I installed a new MC, front rotor/calipers, steal braided lines and new barking brake cables. No amount of bleeding has worked on getting the air out. Not that it has anything to do with the kit, but it sucks that I can't drive my truck.

Hopefully you can figure out the problem and give some feedback on your driving thoughts.
Could u have a small hole allowing air to enter the line while ur trying to bleed them?

 

[Knuckle Dragger]

i bought the kit a few weeks ago. Installed them in about 3-4 hours. It was easy. Only issue I have now is that I can't get the air out of the lines. I installed a new MC, front rotor/calipers, steal braided lines and new barking brake cables. No amount of bleeding has worked on getting the air out. Not that it has anything to do with the kit, but it sucks that I can't drive my truck.

I have found the pressure differential valve in the combo valve(aka proportioning valve) on my truck is very sensitive. Once I open the rears it and holds off pressure to the fronts. It 's the safe guard against a major leak completely taking out the brakes. Pump up the brakes and open a front bleeder to reset the valve and try gravity bleeding the rears after that. I must have bleed a thousand cars over the years and my 94 just kicks my ass trying to bleed the rears.

 

[qwikgta]

I have tried gravity, no joy. i have used a one man bleeder with a pump to suck out the air, nothing. I have had someone sit in the seat and push down the peddle while I open, close the bleeder,zip. I really think it has to do with the fact that the rears were drum and the prop valve/combo valve was for disc/drum. Here's what I have seen. The truck has been sitting and its rained a few times. A small amount of rust has built up on the rotors. When I went out driving yesterday, the fronts were clean and shinny w/ no rust, but the rears still had at least 50% rust on the rotor. You could tell that the rear calipers were not compressing hard enough to remove the rust. I don't understand the factory "rear anti-lock" prop/combo valve enough to understand if its the problem. I have purchased a few parts to bypass the valve. I was thinking about putting a Wilwood prop valve directly off the rear line. Then using it to control the amount of pressure being sent to the rear. Any thoughts?

 

[Knuckle Dragger]

I have tried gravity, no joy. i have used a one man bleeder with a pump to suck out the air, nothing. I have had someone sit in the seat and push down the peddle while I open, close the bleeder,zip. I really think it has to do with the fact that the rears were drum and the prop valve/combo valve was for disc/drum. Here's what I have seen. The truck has been sitting and its rained a few times. A small amount of rust has built up on the rotors. When I went out driving yesterday, the fronts were clean and shinny w/ no rust, but the rears still had at least 50% rust on the rotor. You could tell that the rear calipers were not compressing hard enough to remove the rust. I don't understand the factory "rear anti-lock" prop/combo valve enough to understand if its the problem. I have purchased a few parts to bypass the valve. I was thinking about putting a Wilwood prop valve directly off the rear line. Then using it to control the amount of pressure being sent to the rear. Any thoughts?

Did you try resetting the switch as I described?

 

[Gibson]

You need a combination valve made for a disc/disc system.
Those adjustable Wilwood valves are not a great choice for a truck,, as no one setting can compensate between an empty bed or a heavy load.
The Wilwood valves are best suited for vehicles that carry a more or less constant weight, like a car.

 

[RI Chevy guy]

i bought the kit a few weeks ago. Installed them in about 3-4 hours. It was easy. Only issue I have now is that I can't get the air out of the lines. I installed a new MC, front rotor/calipers, steal braided lines and new barking brake cables. No amount of bleeding has worked on getting the air out. Not that it has anything to do with the kit, but it sucks that I can't drive my truck.

What m/c did you put in? If it's a stock GMT 400 m/c that may be the problem- the calipers and m/c in the 400's were made to pull the pistons back off the rotor when you release the brakes (as a fuel saving measure, bad idea!), just one of the reasons these trucks had such bad brakes. Switching to a GMT 800 m/c from a 2WD 2500 will solve the issue, it does not have the valving I mentioned and a bigger cylinder bore that is not stepped to change front/rear pressures (it is intended for disc/disc) and seems to work just fine with the stock proportioning valve (mounted to the ABS unit). You will need to address the different brake line fitting size at the master cylinder- as I was changing lines anyway I just put the correct size fitting for the m/c on the 1/4" line going back, but there is an adaptor available to convert the thread sizes. Also, if you have ABS, you will need to do an ABS bleed with an appropriate scanner- the last bit of air I had in mine was hiding there and took a while to get out. Hope this helps

 

[qwikgta]

UPDATE: So I put the larger GMT800 master in, after bleeding I had no change, soft pedal all the way to the floor. Bleed, bleed, bleed and soft pedal. Decided maybe it was related to the ABS which is setup for disc/drum. So I decided to delete the ABS. Tried several different methods all including a prop valve made for a disc/disc system and all required me to cut/flare the ends to fit into different parts. I tried my best to flare the tubing but in the end they all leaked. So I decided to match up stock lines with stock flares so I could prevent leaks. I got a hold of some early lines so I had one less fitting to worry about, and used a prop valve from a 06 Burban. So now it goes from GMT800 master to stock lines fitting to the stock prop valve to the stock early lines. No leaks. I've bled it to the point of getting no air, just fluid, coming out of the rotors, and in the end, i still have a soft (to the floor) pedal. Going to try to bleed them again tomorrow but i'm getting real sick of going thru quarts of fluid every weekend and getting nowhere....... more to come.

 

[qwikgta]

Did you try resetting the switch as I described?

yep, even used the prop valve tool that came with my wilwood valve, the one that you install in place of the warning sensor. it stops the side-to-side movement of the internal valve. no joy.