[Greg T]

Hello, folks. Been a while~!
I have a 2000 Sierra 4 wheel disc truck that blew a brake line. My son is doing the work (he's built many rods, and I'm not physically capable) and after inspection, decided the best route to go is to remove the ABS stuff and replumb the brakes. So, he's all brand new line from the front, going to a T fitting and then to each front wheel. The rear is plumbed exactly the same way. He's bled these things repeatedly, but cannot get a pedal. He can pump it up to 1/2 pedal and it will hold, but after being released , the pedal with go to floor when applied again. He did notice a little movement and a couple of bubbles moving in the reservoir after pumping them. Bleed as he may, he cannot get any air from any line.

Okay, question time. Could this be a situation where he needs to install a residual check valve in the rear to maintain pedal? Also, could the MC have been damaged from repeatedly hitting the floor with the pedal?

I've seen many many hot rods built with plumbing exactly like this and they all work. We reused the MC and all the wheel cylinders, just replumbed it all without the ABS.

 

[LATECH]

I would say yes to both questions

 

[75gmck25]

I’ve made the mistake of pushing the pedal to the floor with an old master cylinder and I think the seal was damaged when it was pushed across a ridge/build-up in the cylinder. After that I could pump it up and get enough pressure to bleed the brakes, but it would never hold pressure well in normal use.

 

[Greg T]

I’ve made the mistake of pushing the pedal to the floor with an old master cylinder and I think the seal was damaged when it was pushed across a ridge/build-up in the cylinder. After that I could pump it up and get enough pressure to bleed the brakes, but it would never hold pressure well in normal use.

That was my first thought of what had happened. By all laws, this direct set up should work because the MC is a bit higher than the calipers, although the truck has a 5"x7" drop kit. It's still a direct connection to the MC with nothing in between.

 

[57Nomad]

Why not just replace master cylinder?

 

[Greg T]

Why not just replace master cylinder?

I have one ordered. But I am old school and don't believe in throwing parts at something hoping the symptoms disappear. I like to know what's wrong before I wrench. Since I am not up to speed on the newer stuff, I kinda thought maybe someone had run across this issue before.

 

[2old2fast]

I have one ordered. But I am old school and don't believe in throwing parts at something hoping the symptoms disappear. I like to know what's wrong before I wrench. Since I am not up to speed on the newer stuff, I kinda thought maybe someone had run across this issue before.

That not only gets a LIKE ,it gets a hooray , congratulations , well done !! Too damn many 1-800 / credit card parts changers out there !

 

[Greg T]

That not only gets a LIKE ,it gets a hooray , congratulations , well done !! Too damn many 1-800 / credit card parts changers out there !

It's the way I was raised. It's the way I've always worked, and at age 67+ it's a policy I still live by. I've also instilled this into my middle son who is now 43 and would rather repair/rebuild something than replace it. I still rebuild starters if I can SOMETIMES find the brushes and bushings! LOL

 

[57Nomad]

If that was the original m/c at 21 years you got your money’s worth. Safety first and brakes play a good part of that. Starters don’t fall in the safety column.

For future events like this isolate the m/c by plugging off the output ports and work the pedal if it goes down you will know right away it’s bad m/c.

Just as conversation I have purchased more than a couple m/c‘s brand new out of the box that were NG. So bench bleed the m/c first plug ports and see if pedal as worked stays up.

 

[Greg T]

If that was the original m/c at 21 years you got your money’s worth. Safety first and brakes play a good part of that. Starters don’t fall in the safety column.

For future events like this isolate the m/c by plugging off the output ports and work the pedal if it goes down you will know right away it’s bad m/c.

Just as conversation I have purchased more than a couple m/c‘s brand new out of the box that were NG. So bench bleed the m/c first plug ports and see if pedal as worked stays up.

Well, this is why I'm asking questions, because if the pedal is pumped, it will firm up and hold at about 1/2 pedal. It won't sink. If the pedal is released and then reapplied, it goes to the floor.

 

[57Nomad]

Then you verified it’s NG. The rubber hoses can also hold and release. I just fixed my buddies car doing just that. Replaced hoses (another safety item) flushed system and all is good.

 

[Greg T]

Then you verified it’s NG. The rubber hoses can also hold and release. I just fixed my buddies car doing just that. Replaced hoses (another safety item) flushed system and all is good.

The strange thing is that it's acting exactly the way the old drum brakes acted when they needed adjustment. Pump them a few times and get a good pedal. Release it and hit it again and have no brakes. That's why I was wondering if the rear discs may need a residual valve to maintain pressure and pedal.

 

[Greg T]

Will any other MC (NON-ABS W/booster) bolt onto this truck? Or, is there even a difference? Geeeeez I hate learning new things at my age!! LOL

 

[RWENUTS]

Not wanting to assault your old eyeballs but here’ some info on using a newer m/c.
An extensive thread but good info.

First hand experience with changing to the NBS master cylinder WOW! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

First hand experience with changing to the NBS master cylinder WOW! The 1988 - 1998 GMT400 Chevy & GMC Pickups Message Board

67-72chevytrucks.com

 

[Greg T]

Not wanting to assault your old eyeballs but here’ some info on using a newer m/c.
An extensive thread but good info.

First hand experience with changing to the NBS master cylinder WOW! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

First hand experience with changing to the NBS master cylinder WOW! The 1988 - 1998 GMT400 Chevy & GMC Pickups Message Board

67-72chevytrucks.com

Very interesting info. Thanx, much! That tells me that the MC can be used without ABS! I'll wait until I get the MC installed before I worry about the residual valve. Normally, as long as the MC is above the calipers it should be good. With the 5" x 7" drop kit, this puppy sits pretty damned low.

 

[RWENUTS]

I put discs on the front of my 56 210 Years ago.
had poor brakes until I added a 2lb and 10 lb residual valves front and rear.

 

[Greg T]

I put discs on the front of my 56 210 Years ago.
had poor brakes until I added a 2lb and 10 lb residual valves front and rear.

I know when you have a disc/drum combo you need to have the 10 lb residual on the rear to make up for the springs.

 

[57Nomad]

Keeping the brake pads close to the rotor gives best brake response. The old days of drum brakes it was most effective to maintain the shoes with a slight drag on the drums. This is the same effect keeping response and grab best. The residual valve is necessary on rear drums when fronts are disc. That made the rears movement before the front to maintain stability when braking. Drums have more “stuff” to actuate vs disc. You are younger at 67 years so keeping up with the latest stuff is never ending.

 

[Betterdays]

Proportioning valve in your modified system? Also on the new style Master Cylinder, never let the pedal hit the floor when bleeding. Put a block on the floor to help prevent that.

 

[Greg T]

Proportioning valve in your modified system? Also on the new style Master Cylinder, never let the pedal hit the floor when bleeding. Put a block on the floor to help prevent that.

Yup, I see that now. Never hit the plunger more than 1 inch when bench bleeding, also. Damn new fangled stuff!