Troubleshooting brake pedal

Joined
Jan 17, 2017
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288
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Seattle, WA
Hello,

For various reasons I asked a shop to install new rear rotors/calipers/pads for me. I had bought the truck a few months back and it came with one rear rotor that was very scored due to what looked like a rusty caliper. I let it sit for 4-6 weeks and one day it developed a slow brake fluid leak from that caliper. I took the wheel off and could see that the piston itself was damaged and rotor was not only scored but thickness was below spec. Decided to overhaul the rear brakes with new parts (both sides).

I admit I should have done the job myself but lacking space/time/tools, I found a shop that would do it and include a brake flush for a reasonable rate. However, when I questioned them about the process they would use, it was clear they didn't know the particulars of a Land Cruiser. So I printed off the brake bleeding procedure from the FSM and went over it with them. While the FSM states doing LSPV and BV last, we settled on the mud-approved order of rear passenger, rear driver, LSPV, front pass, front drive. I had to show them where the LSPV was (red flag, I know).

Anyway, I picked it up but while driving the pedal starts out firm but if I hold the brakes, it ultimately goes all the way down to the floor and I lose brake pressure. This is especially noticeable on a long downhill or at a stop pointed down (or up). I did the brake booster Operating and Air Tightness checks (below) but may need to do them again...
  • 1a and 1b were inconclusive for me, hard to tell
  • 2a passed
  • 2b the pedal continued going down

upload_2018-9-30_10-55-54.png


Anyway, I questioned the shop and they claim they bled well, no air bubbles, etc. They said it took a lot of pumping to bleed which I attribute to the fluid system being partially open (via the leak) and the fluid having humidified and gotten gunked up?

So question is - Could their work have caused the type of malfunction I'm experiencing? Any thoughts on what it could be exactly?

From what I've read on here, it seems like it could also be the master cylinder seals. I've read other people hearing a whistling sound while vigorously pumping to bleed (which sounds like the opposite of air tightness). I've read yet others who say the ABS system should somehow be flushed as well...

The shop is offering to diagnose/correct any issues and they will fix or replace the part for free but since it is not the parts they installed and rather the procedure, I'm not sure they'll find any fault. Still could be worth trying though as boosters look expensive.

Appreciate any thoughts/advice
 

Tedward

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May have ruined the master cylinder bu pumping the pedal through the full range. Sometimes the old seals give up after bleeding this way.
 
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May have ruined the master cylinder bu pumping the pedal through the full range. Sometimes the old seals give up after bleeding this way.
Is there any way to test the master cylinder or is it more common to overhaul the seals? Assuming Toyota sells a kit.

Since they say it took a lot of pumping, I can definitely see someone trying to rush the job rather than depressing slowly and half-way.
 
Joined
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Sounds like master cylinder, but also check for fluid leaking out anywhere. If it's missing fluid it of the reservoir you have a leak somewhere.

A while ago, I had brake issues in another vehicle. Thought I was up for replacing master cylinder, but it turns out I had a pin hole leak in a rubber line.

Air in the system week usually leave you with a soft spongy pedal feel. Sometimes pumping the brakes a couple of times will firm it up briefly
 
Joined
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Messages
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Seattle, WA
Sounds like master cylinder, but also check for fluid leaking out anywhere. If it's missing fluid it of the reservoir you have a leak somewhere.

A while ago, I had brake issues in another vehicle. Thought I was up for replacing master cylinder, but it turns out I had a pin hole leak in a rubber line.

Air in the system week usually leave you with a soft spongy pedal feel. Sometimes pumping the brakes a couple of times will firm it up briefly
Good point - I did check for a few days after the work and fluid level in the reservoir was constant. However I'll check again. Also thinking I should just replace all the soft lines in case one of them has perhaps lost some structural integrity.

Guess I'll look for a master cylinder kit and start there. I'm just confused, that fluid is either getting very compressed or going somewhere..
 
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Fluid doesn't compress.
It's either leaking externally (hose, loose fitting etc), or internally (shot seals in MC), or has air in the system.
Air does compress, which is why air gives you a squishy, soft pedal feel from the get go.
A leaking MC will usually have a firm pedal, but the pedal well slowly sink to the floor as you hold pressure on it.


These can be a real PITA to bleed successfully 1st go, especially the LSPV.
 
Joined
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Seattle, WA
Fluid doesn't compress.
It's either leaking externally (hose, loose fitting etc), or internally (shot seals in MC), or has air in the system.
Air does compress, which is why air gives you a squishy, soft pedal feel from the get go.
A leaking MC will usually have a firm pedal, but the pedal well slowly sink to the floor as you hold pressure on it.


These can be a real PITA to bleed successfully 1st go, especially the LSPV.
Doh, of course, wasn't thinking on that one. Rather than simply re-bleed the system, replacing seals in the MC seems like a good baseline item to take care of now - thanks. Do you also bleed the bypass valve (BV) during this process?

I wonder if anyone has had good experience with a reverse bleeder on these trucks?
 

bajaphile

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You should find your nearest dirt road/parking lot and try to engage the ABS.

I've read various posts on MUD that after a brake job like described in your post, you may need to cycle the ABS to bleed any air.
 
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Is there a way to do this without driving it?
You should find your nearest dirt road/parking lot and try to engage the ABS.

I've read various posts on MUD that after a brake job like described in your post, you may need to cycle the ABS to bleed any air.
 
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You should find your nearest dirt road/parking lot and try to engage the ABS.

I've read various posts on MUD that after a brake job like described in your post, you may need to cycle the ABS to bleed any air.
Is there a way to do this without driving it?
I've read the same thing but don't really understand why or how that works. I did read one about using a reverse bleeder to achieve the same outcome but need to dig into the FSM and diagrams to understand how that works.
 
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I've read the same thing but don't really understand why or how that works. I did read one about using a reverse bleeder to achieve the same outcome but need to dig into the FSM and diagrams to understand how that works.
I always do a power bleed, I think the shop you used was clueless on a proper bleed, where are you located, I can maybe come by and see what is the real problem, might just be a s***ty bleed
 

Tedward

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I also read a million posts about bleeding. Somewhere in the mountains of thread/posts I read how to make the abs actuator, umm actuate. Never did that though as i pulled the whole giddy up out. The last time i did brakes i did it alone with the old mighty vac. It worked. Anyhoo, if @shocktower is willing to lend an experienced hand, take him up on that!
You'll get it eventually.
And like @Tools R Us, I'd sooner buy a new master than mess with a master brake seal kit.
People go on about being so hard to bleed, I for one dont find it so hard to do. I guess it's the lspv and actuator that thrown in that make it more important to follow the order of operations. But there again I pulled the lsvp so its striaght forward on my wagon.
The possibly failing master also adds to the confusion. If you can swing the expenses just replace it.
 
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Tennessee
One thing you might check that ended up being my problem for the same concern (firm pedal that slowly goes down). My rear caliper slides were froze up on the LH side. Might want to just verify that those are freed up. You'd think that the shop would have caught that right away, but we all miss things sometimes.
 
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I also read a million posts about bleeding. Somewhere in the mountains of thread/posts I read how to make the abs actuator, umm actuate. Never did that though as i pulled the whole giddy up out. The last time i did brakes i did it alone with the old mighty vac. It worked. Anyhoo, if @shocktower is willing to lend an experienced hand, take him up on that!
You'll get it eventually.
And like @Tools R Us, I'd sooner buy a new master than mess with a master brake seal kit.
People go on about being so hard to bleed, I for one dont find it so hard to do. I guess it's the lspv and actuator that thrown in that make it more important to follow the order of operations. But there again I pulled the lsvp so its striaght forward on my wagon.
The possibly failing master also adds to the confusion. If you can swing the expenses just replace it.

I have done many other cruisers and I bleed them by myself, and the only time I have a problem is when there is something wrong mechanical, I love my garden sprayer bleeder
 
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