First brake pedal stroke (1 Viewer)

[spressomon]

This has been an issue with my LC since I got it...and I think I remember others here have experienced the same...the first pump of the brake pedal acts like air in the line (additional pedal travel) and the second pump of the brake pedal feels the way its supposed to. I have thoroughly bled the lines/cylinders numerous times to no avail.

Any one else have this problem? Anyone know the fix?

Thanks in advance

 

[Augie]

I have that problem before but it went away after I rebuild the rear caliper. The inside piston on one of my rear brake seize up due to improper protective booth install by the previous person that touch it. I was pretty worried if that was my master cylinder since its pretty expensive from what I heard.

 

[spressomon]

I have that problem before but it went away after I rebuild the rear caliper. The inside piston on one of my rear brake seize up due to improper protective booth install by the previous person that touch it. I was pretty worried if that was my master cylinder since its pretty expensive from what I heard.

I installed new (rb) rear calipers...so maybe one of the front pistons is stiff/stuck. I'll check that...hopefully its that simple (and cheap (relatively!!!)

Thanks Augie.

 

[tech_dog]

I'd bleed again before I started changing parts. Be sure you bleed in the order recommended in the FSM, including bleeding at the LSPV, if I remember correctly.

It often takes quite a while to chase all the air out of the sytem.

 

[spressomon]

I'd bleed again before I started changing parts. Be sure you bleed in the order recommended in the FSM, including bleeding at the LSPV, if I remember correctly.

It often takes quite a while to chase all the air out of the sytem.

This problem has been persistent since I bought the rig some 18-months ago. Bleeding the wheel cylinders doesn't change it. I ran 2-1/2 quarts of fluid through them during 3-separate cycles even tapping the calipers with a wooden dowel to help release any trapped air pockets (since I started with new rear calipers). No bubbles when I was done with the bleed process. However the FSM mentions bleeding the Brake Booster...but unless I am way inept I can't find where it shows how to do it...

What is "LSPV"?

 

[Landpimp]

our LX acts the same way, seeing how its Connie's driver.......I don't worry about it

 

[100 TD]

What is "LSPV"?

Load sensing proportioning valve......... this is built into the master cylinder now so besides bleeding the master cylinder you would not need to worry about it. (My thoughts without checking the manual)

 

[a990dna]

I've chased brake problems before.. not fun. You may want to take it in for a full flush and pressure bleed. I've never heard of bleeding the Booster... I thought that was vacuum driven. Unless they're referring to the Master Cylinder as the "Booster". The Booster and MC on mine looks one-in-the-same and there may be a way to bleed this unit, although I can't find a typical valve as well.

Are you sure it's not the front calipers causing the problem?

 

[spressomon]

I've chased brake problems before.. not fun. You may want to take it in for a full flush and pressure bleed. I've never heard of bleeding the Booster... I thought that was vacuum driven. Unless they're referring to the Master Cylinder as the "Booster". The Booster and MC on mine looks one-in-the-same and there may be a way to bleed this unit, although I can't find a typical valve as well.

Are you sure it's not the front calipers causing the problem?

Don't know yet...when I reassembled the brakes a couple weeks ago they appeared OK...it would be nice if it was as simple as replacing the calipers.

 

[a990dna]

As an FYI... I've experienced calipers sucking air (as opposed to leaking) past the pistons. The reason was pushing the pistons back and scoring the o-rings with brake dust that had seeped past the boots. Although this was many moons ago and on two different GM vehicles.. the first time it happened my reaction was to swap out the MC.

This may or may not be your problem. I chased brake issues on my other vehicle for years. I finally gave up after spending $$$$ on all new parts---the only thing I didn't change was the fixed steel lines. After all that the pedal was better but could still push it to the floor with enough pressure.

 

[lowenbrau]

A loose wheel bearing will produce the same symptoms. First pump straightens the rotor in the caliper, second applies pressure to the pads.

 

[spressomon]

A loose wheel bearing will produce the same symptoms. First pump straightens the rotor in the caliper, second applies pressure to the pads.

Nope...definitely not loose wheel bearings on mine.

 

[Landpimp]

nor on ours........I wish

Nope...definitely not loose wheel bearings on mine.

 

[calamaridog]

Mine does the same thing. It still works, but is mushy. I pump it once before I pull out and everything firms up.

 

[lexs470]

rusted or frozen calliper slider pins. have the calipers opened up and use slider grease in the sliders then assemble the calipers back again. that should do the trick. do it at all four sides.

 

[a990dna]

You're right, this is often overlooked. My dad taught me how to do break jobs when I was very young. He always used emery cloth to clean all metal contact points and would use high temperature grease on those areas. He would also chamfer in-running edges on pads/shoes and cleaned the disks/drums with laquer thinner. He said this would prevent chatter like you can get when replacing a clutch.

I'm sure this is very old school, I rarely see mechanics go to this extent when performing brake jobs.

 

[a990dna]

here's a visual... not exactly a Land Cruiser but it'll do.

http://www.bikersoracle.com/jaws/brakeoverhal.htm

 

[spressomon]

rusted or frozen calliper slider pins. have the calipers opened up and use slider grease in the sliders then assemble the calipers back again. that should do the trick. do it at all four sides.

New pins, pads, rotors, brake fluid and ss lines...same symptom as before all the work was done. I, because the front caliper pistons floated nicely, did not rebuild/replace them...

 

[vxlc80]

any update?

 

[spressomon]

No...but I'm finally going to overall the MC next week. So hopefully, that along with a couple other brake system mods, will finally put this to bed.