94 Suburban C1500 MC upgrade and 4WAL bleeding

[ShannonTxBurb]

My vehicle

94 Suburban C1500 5.7L-350 Silverado trim 365,000 miles

Stock braking system at the start.

I let the burb sit for a few months and then got in it to get it back on the road. The brake pedal when to the floor and about the last two inches before hitting the stop, it managed to apply enough brakes to stop.

The brakes had been spongy for a while, a little more spongy than when new. They always had too much pedal travel for my taste but about half travel would engage the brakes and they worked. After renting a few new trucks and SUVs, the pedal on the bueb is not acceptable.

I bought Russell braided steel flex lines but hadn't put them on yet. I made a run to Summit and got the Power Stop Z36 kit, new rotors, calipers, pads. I figured replace it all at once.

I also read on here about the NBS MC upgrade. So I got a MC for a 2002 Tahoe with a 1.46" bore. I got it bled and installed. (Only part changed so far.)

I still have about 75% of pedal travel before I get brakes, but it does engage the brakes. I am not losing fluid anywhere. So I read that this is probably the 4WAL module.

Two questions:

1 Is the MC I chose OK for the basically stock brakes? NMC11122 at O'Reilly

2 What is the most reliable way to bleed that 4WAL KH module?

Other options?

 

[SUBURBAN5]

Theres a bunch of mixed feelings on the mc upgrade. After all the confusion I came to determine JB6 brakes on the burb is good enough stock. Now that being said if all you did is correct and working normal then bleeding the mc is a pain but I believe the best way is the bench bleed it first, then bleed the lines hooking up to it then bleed the ky bleeder, then bleed the wheels furthest to closest. Now I've never installed my mc. I always had the dealer do it but if I had to then this is how I would of did it

 

[SUBURBAN5]

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See if these help a little

 

[ShannonTxBurb]

I don't think that answers either of my two questions. Thanks for the effort though.

 

[TheAutumnWind]

I don't think that answers either of my two questions. Thanks for the effort though.

question 1 is that mc right for your stock brakes? Some would say no. You have calipers designed for the stock MC that has qtu design. The new MC does not have that. It actually provides less overall braking pressure despite having a better initial feel. If you did an nbs brake upgrade it would be different.

You may be better off with a new stock MC IMHO with fresh fluid and fresh calipers and good pads...

2. Reliable way to bleed module. You can try getting abs to activate on a gravel road with a hard stop. I'm sure other can provide more input here.

 

[ShannonTxBurb]

The Z36 kit, new calipers and rotors, and the braided steel flex lines, are next. I need to fix the current system ASAP so I can get the safety inspection and tags and start driving it again. Since I'm not losing fluid, I don't think replacing any of those parts will make a difference in the pedal going nearly to the floor. It's not safe to drive as is.

 

[Pinger]

I have a similar thing going on - seem my thread for all the details.

Briefly though, I'm between it being a MC issue and ABS one (probably air in the ABS unit). I intend trying to bleed it mechanically as per the two videos (though I bench bled first and did bleed at the pipe unions and wheels). If that doesn't work and the suspicion is still air in the ABS unit then it looks like I'll have to bite the bullet and buy the Tech II scanner and force the ABS bleed with that as that appears to be the only sure fire way to bleed the ABS.

It doesn't to me feel like air in the system (hence suspicion of failing MC(s)) but I'm basing that on my experience with air in main circuits - not the in the ABS unit.
I'm hoping to get the bleeding done in the next couple of days and will update my thread once I have.

 

[TheAutumnWind]

The Z36 kit, new calipers and rotors, and the braided steel flex lines, are next. I need to fix the current system ASAP so I can get the safety inspection and tags and start driving it again. Since I'm not losing fluid, I don't think replacing any of those parts will make a difference in the pedal going nearly to the floor. It's not safe to drive as is.

If the pedal is going to the floor you have air in the lines.

 

[HotWheelsBurban]

If the pedal is going to the floor you have air in the lines.

Yes,because air compresses and brake fluid does not. You need a pressure bleeder. Both times I or my mechanic friend worked on the hydraulic parts of the Burb's brakes, we used the one Harbor Freight sells. It's around $35 and well worth it; makes the job doable by yourself. Only thing I needed to fix was a wire frame to hold the bottle in place that sits in the master cylinder.
He changed the master cylinder and rear wheel cylinders in 2016, and I replaced the front calipers and brake hoses in 2018.

 

[TheAutumnWind]

Yes,because air compresses and brake fluid does not. You need a pressure bleeder. Both times I or my mechanic friend worked on the hydraulic parts of the Burb's brakes, we used the one Harbor Freight sells. It's around $35 and well worth it; makes the job doable by yourself. Only thing I needed to fix was a wire frame to hold the bottle in place that sits in the master cylinder.
He changed the master cylinder and rear wheel cylinders in 2016, and I replaced the front calipers and brake hoses in 2018.

I have the harbor freight bleeder that you hook an air compressor to. Works great! Just keep the mc topped off.