Spongy brake pedal

[k10mojo]

Hi all, I recently installrd a new 4 inch lift kit and new wheels on my Suburban. Problem is I have hardly no brake pedal now, before it was great. So I bled the brakes at all 4 wheels and ita not helping so I was thinking maybe the mastercylinder is bad, what do yall think?

 

[JoeR Jr]

Hi mojo,
It's way more likely you have air in the master cylinder, brake lines, wheel cylinders or calipers. The master cylinder probably didn't fail at the same moment you opened the brake lines.
It's not impossible, but unlikely.
Bleed the master cylinder.
Re-bleed the brakes.
Joe

 

[PrairieDrifter]

Start with the RR then LR then RF then LF. If it worked great before then it’s unlikely it failed like said above. Sometimes it can be a bitch to get brakes bled

 

[roundhouse]

Did you replace the rubber flex lines with longer ones ?

If not you need to
The factory ones are not long enough for a lift kit

Bleeding is pretty straightforward
Get a helper
Start at the RR
Work put some communication with the helper
When you say “down “
After they mash the brake pedal have them repeat “down”
So you know when to crack open the bleeder screw

And after you close the screw say “up” and have them repeat it when they let off

Do this until you don’t get air from the bleeder screw

I will take 15-20 bleeds or more

Then move to the LR
Then RF then LF

If that doesn’t fix it you could have a bad master

THey don’t cost much so you could replace it before you start bleeding

But buy a NEW master made in the US

Not a used one that was rebuilt in Mexico or China or a new one made in China

If you replace the master be sure to bench bleed it first

It comes with instructions and small rubber tubes to do this

Clamp the master in a vice
You connect the tubes to the outlets and loop them back into the master tank

Fill the master and use a screwdriver or something to mash the piston in a little bit

Do this till no more bubbles come out of the tubes

Then when you install the new master and fill it you can open all the bleed screws and go have lunch

When you come back the lines will be filled and fluid dripping out at he wheels

You still have to bleed some air out but it saves some time

When you are bleeding ,keep an eye on the level on the master

If you let it run low or out , you gotta refill it and start all over again


A lot of times the old master will have wear pattern in it because it doesn’t ever go all the way to the floor

When you bleed an old master you’re running the piston way past where it has been sliding for the last 20 years and sometimes that will damage the O rings in the piston

Usually you can tell if a master is bad
Crank the car and mash the brakes hard and keep em mashed
If the pedal slowly moves to the floor , the master is bad

If it doesn’t move slowly to the floor it’s usually good

Most of the pedal feel comes from the rear drums and shoes
If they are not adjusted properly the pedal will travel too far down before it does anything

 

[73c20jim]

I use gravity bleeding. I open all the bleeder valves and watch the fluid drip out of each caliper. My job is to keep the master full and drink beer.

This is done after the master is bled.

YMMV.

 

[idahovette]

I use gravity bleeding. I open all the bleeder valves and watch the fluid drip out of each caliper. My job is to keep the master full and drink beer.

This is done after the master is bled.

YMMV.

I open them one at a time and let em flow. Takes longer=more beer

 

[Craig 85]

Do you have a valve that looks like this just ahead of the rear axle on the passenger side? I know both my '87 trucks had this. I don't recall if my '88 Surburban did though. If you have this valve and it is not lifted/lowered the corresponding amount as the lift, your rear brakes won't work. They were designed to give more rear brake bias when loaded. By lifting the truck it removes brake pressure as if the truck is totally unloaded.

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[73c20jim]

I open them one at a time and let em flow. Takes longer=more beer

Excellent point. I will try that next time.