Bleeding brakes on 2000 Chevy 350

Geo-TH,In · Sep 7, 2017

Friend is having trouble bleeding brakes on truck. He put new master cylinder on it. Bench bleed it. Bleeding master cylinder on truck. Can't get back brakes to

It's like the master cylinder is leaking fluid back in reservoir. You see fluid getting push back into reservoir, not making pressure.

Any ideas?

Bob · Sep 7, 2017

If he "stroked" the MC more than a short distance when he "bench bled" it the cups could be torn or out of place.

Often, the instructions packed with a MC explain this/what's a safe stroke distance.

In today's world it's not impossible the new MC is "bad" from the start, either.

farmer boy · Sep 7, 2017

There's a proportning valve on the back of the ABS module that can prevent fluid from passing in the event of failure. From what I understand, there's a tool for this, but I've also read that a real sharp jab of the pedal can reset it. The ABS also should be bled. You need a bi directional scan tool to do so.

Steve@Advance · Sep 7, 2017

If he's seeing a little fountain of fluid coming up the the reservoir when the pedal is let up, that is an indication of air in that circuit.

Might try pressure bleeding from the rear back up to the mc. A new, clean, oil free, oil pump can with a piece of hose on an open wheel cylinder bleeder will sometimes work.

Anti lock brakes can be difficult to bleed. On some Fords the anti lock has to be tricked into running to get the air out, not sure on GM.

Geo-TH,In · Sep 7, 2017

Steve, just tho opposite, a stream of fluid comes up when brakes are applied. He took MS back. Going to wait to get a new one in tomorrow.

Is there a special way to bleed ABS brakes?

Crazy Horse · Sep 7, 2017

No shortage of You Tube videos ...... and of course, you depend on the guy filming to know of what he speaks.
Chev anti lock brake bleeding

Hobo,NC · Sep 7, 2017

Fluid will squirt back into the reservoir its the nature of the beast...
As Bob said short stroke the master while bench bleeding about a 1" You will see it squirt back into the reservoir at that time... Do not press the brake pedal all the way down while depressing the brake pedal it can damage the master cly.

Make sure he got the correct part BTDT liked to never figured it out...

He may just have to pay a overpaid mechanic to fix it for him

guido · Sep 7, 2017

Hello Geo-TH,In,

Here is how I have done it since I was shown back in the sixties by a postman.

Take a hose that fits the bleeder long enough to reach from the farthest bleeder to where you can see the end. Take a clear jar and put in enough fluid to cover the hose. Fill the master cylinder. Open the furthest bleeder and push and release the brake pedal. You can use your hand slow all the way down and release it. If there is air in the system you will see it bubble in the clear jar. When you release the brake pedal ONLY brake fluid goes in the line, NO AIR!.....Neat? Repeat the brakes actuation until bubbles clear. Check the fluid often so you won't introduce more air in the system.
The postman was my landlord back in the late 60's. Nurenburg Germany Postmaster........ True story!

Guido.

chevytaHOE5674 · Sep 7, 2017

Sometimes when you get air upstream of the ABS module it can be almost impossible to bleed without a proper OBD scan tool that can move the ABS valves to get the air out.

Hobo,NC · Sep 7, 2017

THAT'S WONDERFUL but that wuzz yesterday..

That still could apply if all the stars in the universe aligned BUT he done fudged with it its gonna cost him..

Geo-TH,In · Sep 8, 2017

HOBO..
I'm more likely to spend money to fix something than my neighbors are. I
thinking master cylinder was damaged by pushing peddle all the way to the
floor. I'll put a 2x4 under peddle on new master.

He could have pushed too hard when he purged it on the bench.

This 350 has a hydraulic brake assist. It runs off power steering pump. So do
you have to have engine running while bleeding brakes? Never seen one before.

I think he may have jumped the gun and replaced a good original master
cylinder. I discovered the brake line to rear wheels was leaking big time,
major rust.

Hobo,NC · Sep 8, 2017

Bleed engine off. Leaking line = more fuel to the fire...

Hobo,NC · Sep 8, 2017

http://forums.yesterdaystractors.com/viewtopic.php?t=1243562&highlight=bleeding

Don't let the ABS confuse Y'all it may not be a problem. I spec bleeding the fronts are going to go well. The rear brakes are normally a problem child... If you are not getting fluid out a rear bleeder go back to a front open a bleeder and slam the brake pedal hard that will center the combination valve and allow fluid to go the the rears. Close that bleeder Then go back to the rears and be genital with the brake pedal so the CV does not close off the rears again.

Chebbys are just plain mean to bleed most are not what I call a free bleeded :evil: Some are tho it depends on what ABS system they have.

Special tool for bleeding some GM ABS systems Google "j39177 tool"... I have never had any luck with this tool myself. I have a pressure bleeder GM trucks are one of the few I like to always go back and crack the bleeders manually after a system bleed/flush. They are pron to letting air past the rear wheel cylinder cups its hard to get all the air out.

guido · Sep 8, 2017

Hello Geo,

You can use your hand to push and release the brake pedal if you use my method. One man job to boot!

Guido.

Bleeding brakes on 2000 Chevy 350

Geo-TH,In

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Bob

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farmer boy

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Steve@Advance

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Geo-TH,In

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Crazy Horse

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Hobo,NC

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guido

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chevytaHOE5674

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Hobo,NC

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Geo-TH,In

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Hobo,NC

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