Brakes. WTF am I not doing / doing wrong?

[exp500]

I asked for part numbers installed because details matter. With 10" rear W/C you could get from 7/8"-1 3/16 cylinders. Did you measure them or just trust AZ? Master cylinders are 1-1/16 to 1-5/16.
If you think bleeding is still the problem after a gallon of fluid, Jack up rear before bleeding again. Slowly Stroke the brakes a few times while motive pushing fluid. Last is Back up slowly , Jab brakes hard/release quickly while still moving a few times to bring your adjusters up. You should feel that in pedal after. Hope you get it fixed. I'm done.

 

[96-2D-Hoe]

Jack up rear before bleeding again.

Thanks for the reply. This is something I thought of also. The rear is a couple inches lower than the front every time I bleed it. The next time I do it, maybe today, I am planning on turning the truck around so the back is higher.

But like I already mentioned I'm pretty certain the ABS still has air in it and I'm going to set it off a couple times and bleed to see if that is the case.

The previous 'rebuild' I did in 2016 was all crap from AZ. I had the same issue then. Setting off the ABS and bleeding a bunch of times fixed it. I thought the Tech2 would change that.

The Tech2 only lists 'ABS Bleed' for 98+. I suspect the 'Function Test' for 96/97 is not the same although it does move something.

All the rear brake parts were Delco from RA for my 10" brakes. I didn't list them because I know I bought the correct parts, but FWIW

ACDELCO 17593R {#14593R, 18030019, 18038916} (Daily Driver) Professional; Riveted Info
Rear; w/ 10" Rear Brakes

ACDELCO 18E1234 {#18029476, 18E296, 19175763} (Daily Driver) Professional Info
Rear; w/ 10" Rear Brakes

ACDELCO 18B202 {#18028515, 19176963} (Daily Driver) Professional Info
Rear; 4WD; w/ 10" Rear Brakes

ACDELCO 18K73 {#18034447} Professional Info
Rear Left; w/ 10" Brakes

ACDELCO 18K74 {#18034448} Professional Info
Rear Right; w/ 10" Brakes

The AZ MC was still under warranty from 2016

• 
  Duralast New Master Cylinder (Brake System) NM3034
  • Part # NM3034
  • SKU # 269027
  • Warranty:
  • 4.2
    (20)
• Application: With gasoline engine, With JB5, JB6 brake system
  Notes: With reservoir, Under 7200 lb GVW.

 

[exp500]

3034 master= 1 1/4
18E1234= 1.18
should work good if rears will lock on pavement.
Jack rear of truck High when bleeding. Piston moves.

 

[96-2D-Hoe]

Thanks for all the advice and replies.
Had to swap out MC's again as I guess it was more than just the reservoir seals leaking. I had used the one that had the nicest machining, but it still leaked/weeps. Swapped out seals and reservoirs once more this evening and I don't think this one is leaking thank ****. Brakes didn't change much at all and I haven't bled them again yet.
Getting there, slowly

 

[96-2D-Hoe]

FYI the Motive 105 kit/plate does not work well with the GMT400 MC. I used it today and I must have damaged one of the reservoir seals trying to seal it as now another MC is leaking/weeping. I'm hoping it may plump itself up and seal again overnight/ in a day or two.

I pressured it to 8PSI and again the reservoir was starting to deform at the back. So I put the rear chains around the reservoir. I left the front chains around the MC and that seal is now leaking.

Using it at 6-7PSI it's also not really pushing the fluid through very fast and I think one or two man bleeding would likely be more effective. It also leaked a bit and so the reservoir got completely full of fluid and spilled when I took the plate off.

You may have more luck using a clamp between the reservoir and the plate, but I doubt it.

I don't think it is much if any faster than bleeding it on my own pushing the pedal. And there's probably more pressure going through the system doing that.

I'll probably return mine.

I adjusted up the rear brakes a couple clicks but didn't notice any difference in the pedal. I took it to some loose ground and set the ABS off a couple times getting my truck covered in dust and crap. When I got home I found the MC weeping and didn't bother to bleed again. The pedal still sucks but the brakes do work.

If the MC seals back up I'll try bleeding some more. If not I will buy a Delco MC from RA and start again.

 

[exp500]

Some people have trouble with the 105, even in the old days of cast M/C reservoirs. Others built their own from steel plate that worked better. 3/8 plate and a c clamp is what I use. About 8-10 # works fine.
Your M/C weeping from reservoir seals? Thats a NO GO condition. Weeping from Vac booster area a NO GO also. Thats a cut seal, warped tube or dirty seal. Gotta be careful installing reservoir, and install wet. same with seals. This stuff doesn't fix itself. Just becomes a total failure issue. Take your time, learn the signs and signals, Finess not brute force. Use your Tech 2 to open the ABS while bleeding.
I explained easiest way to adjust rear drums also. When you adjusted them was wheel jacked and spun after clicks? You keep shortcutting. Are you doing piecework? Flat rate?
Another option for bleeding is a stick between the seat and the pedal. Pain in theA## but works. Some have a spring in tube(s). Gravity bleed gets enough thru that you only have to pump 3-4 times each wheel.

 

[exp500]

Lastly, there are a few threads about using newer M/C with a screw cap in this vintage. I don't recommend this UNLESS you find a stepped bore M/C the same size you have. Hint- Look at repair kit Diameters.
Also- look in reservoir- if plastic is bright white around connecting tubes, then you bent it(reservoir) and its junk.

 

[96-2D-Hoe]

I'm just shortcutting in my description. I did jack the wheels up and check rotation after adjusting. I said a couple clicks because the rear brakes were just installed and that was all it took.
I followed the service instructions, replace MC, bleed, run ABS and bleed again. I saw one medium bubble and one tiny bubble come from the rear right. I used over 1/2 gallon fluid in total. Nothing from anywhere else.

Then I went to set the ABS off and when I came back there was loads fluid around the MC that I had thoroughly cleaned before I left.
I'm considering pulling off the reservoir on the truck and replacing the seal but I'm not sure if I'm just wasting my time again. I'm also completely over it at this point. Everything was wet when I swapped it out previously. It doesn't come off easy but pops back on without any issue. The aftermarket reservoirs are junk and some plastic around the holes was bright white even before I took it off.

I'd already road tested the MC the night before and it was not leaking until after I used the Motive. The rubber on the plate is the issue. It is way too hard and can't give enough to seal. I even put it on tightened it up some and waited 20 mins in the hope the rubber might give. But it doesn't.

I'm not going to bother with the Motive again. By the time I screw around getting it sealed I could have the two rear brakes bled. And that's without the damage it's causing.

I still have an Autozone MC to return so I have a couple seals I could use. I'm really not sure what to do next as I'm completely fed up with wasting my time on this.

 

[iamdub]

I've never used anything other than a water bottle with clear vinyl hose in it, the ignition key and my leg to bleed the brake system, including the ABS.

I bleed them like any normal method, but right as I begin to stroke the pedal, I turn the key to "on" (not start). The ABS computer cycles the solenoids at power up as a self test. With the fluid under pressure, being pushed towards the rear, it flows as soon as the valves in the ABS are opened, carrying any air with it. I do turn the key on maybe every 4-5 strokes. I also push slowly. Some people pump the pedal as if they're trying to kickstart a dirtbike.

If none of these work, then it has to be a faulty MC or it wasn't bench-bled properly.

 

[96-2D-Hoe]

After all the doom and gloom it seems like it has sealed itself up some. Regular braking is not making it leak. I drove around for 20 mins and stopped to check it a couple times. It may weep slightly but not enough for me to want to take it off or screw with it again right now. If I find it's leaking badly I'll buy a Delco.
For now I'll just carry on bleeding like I've done in the past.

The ABS computer cycles the solenoids at power up as a self test

I can't say I've ever noticed anything like this. Are you sure that's the case for a 96?


FYI
In my defence I screwed with the brakes when I first got the truck and somehow let a bit of air in. Dealer took 3-4 tries to get it right. The brakes on these trucks are a PIA.

Edit
I just did the ABS function test and nothing leaked so phuck it it's staying for now. Back to bleeding.

 

[iamdub]

I can't say I've ever noticed anything like this. Are you sure that's the case for a 96?

Now that you mention it, I'm second-guessing myself on this particular vintage.

 

[thompsoj22]

Are you going all the way to the floor with the pedal? Try half strokes for one complete bleed sequence. I know it sounds impossible but try it and see, In fact since you feel the rears are the issue just do those and leave the fronts alone. ill bet the pedal firms up instantly. This is a big hail mary bet!

 

[96-2D-Hoe]

Are you going all the way to the floor with the pedal? Try half strokes for one complete bleed sequence. I know it sounds impossible but try it and see, In fact since you feel the rears are the issue just do those and leave the fronts alone. ill bet the pedal firms up instantly. This is a big hail mary bet!

Thanks for the reply/advice. I don't push the pedal all the way to the floor any more. I killed at least one MC doing that the last time I went through this. Probably about 1/2 way or so.

I only had about a quart fluid left so I just put it through. I got a couple bubbles from the passenger rear. Not sure about the rest as it's hard to tell when you're one man bleeding. About to return the spare MC to Autozone so I'll see if it's any different shortly.

 

[96-2D-Hoe]

Considerably better. Pedal was going past halfway. Now probably travels about half of what it did before. Finally got somewhere. And that is why I wanted to set the ABS off.

No problems returning the frankenMC to autozone. Bought the 4th gallon of brake fluid, and an additional ground cable to run from the battery to the frame with my free points money.

Didn't check the MC for fluid when I got back. Hoping it's dry tomorrow when I carry on.

 

[96-2D-Hoe]

Ahh well. Here's an update.

 

[96-2D-Hoe]

Lastly, there are a few threads about using newer M/C with a screw cap in this vintage. I don't recommend this UNLESS you find a stepped bore M/C the same size you have. Hint- Look at repair kit Diameters.

There's probably a cheaper way but I came across this and thought I'd put it here
https://www.littleshopmfg.com/gm-ck1500-master-cylinder-upgrade/

 

[96-2D-Hoe]

Fed Ex suck and just delivered my RA order.

The Delco MC reservoir is night and day to the Duralast from AZ. The plastic is stronger, the lip around the top is completely level and flat and it fits to the body much more securely than any I got from AZ.

Hopefully this saga will be over soon.

 

[96-2D-Hoe]

Sadly my pedal still sucks, but the brakes do work, and now I need a brake booster. It has been hissing inside for a while, but now it's hissing under the hood too. Still works though.

RA has an new SKP with no core exchange for $75. The rest are remans and there is no Delco option.
Any recommendations?

 

[exp500]

Put a vacuumn pump on it and check leakdown time. Or the brakeclean spray trick while idleing, though I don't recommend that. If your brakes are soft you have AIR in the master or elsewhere.
Maybe its technique, pumping brakes too fast while bleeding maybe? I know firsthand about brake part issues with these- hoping you aren't caught in 5 bad ina row- I buy brake fluid by the gallon.
Again- are the rears adjusted tight? that brings pedal up 3/4-1 inch. Constant battle with the self adjusters about once a month to bring them back up. Rear brakes still last 2 years.

 

[George B]

Put a vacuumn pump on it and check leakdown time. Or the brakeclean spray trick while idleing, though I don't recommend that. If your brakes are soft you have AIR in the master or elsewhere.
Maybe its technique, pumping brakes too fast while bleeding maybe? I know firsthand about brake part issues with these- hoping you aren't caught in 5 bad ina row- I buy brake fluid by the gallon.
Again- are the rears adjusted tight? that brings pedal up 3/4-1 inch. Constant battle with the self adjusters about once a month to bring them back up. Rear brakes still last 2 years.

Good advice about self adjusters. Brake adjustments were part of a tire rotation for me when I had Drums. However I believe the OP has done this already.
One thing I didn't see and would like to confirm is have the rear wheel cylinders been replaced. If so, are they the right bore diameter? There can only be a couple things wrong here:

1. Air in the system
2. Bad master cylinder
3. Mismatched parts
4. leaks