Brake System Failure - Bring me up to speed (2 Viewers)

[cruiseroutfit]

You guessed it, another ABS/VSC 'lights on' thread. I just picked up a 2000 100 with known brake issues, i.e. zero brakes at all including the park brake. It didn't take more than a few minutes to figure out the park brake bell cranks were seized, I've been down that road countless times over the years, parts are sitting here for time on that project.

Now onto the more pressing issue (pun intended), no brake assist. I picked this up last Thursday (wrecker delivered) and have literally had less than 5 minutes to work on since then. What I do know is that it has zero brake assist, the brake booster pump doesn't seem to be spinning at all and the master is overfilled and looks to either have leaked from the overfill or possibly out of the cylinder all over the ABS module and pump, hard to definitely tell where all the fluid is from but its a mess. Previous owner had a shop look at it and they told him the ABS 'system' failed because of the leaking master cylinder? I suppose that could hold true? I've spent the last hour combing through the depths of Mud and have founds some extremely helpful threads, I'm comfortable rebuilding the master cylinder if needs be but that only addresses half of my assumed issue. I've read the pump was not made to be serviceable? Anyone confirm or deny that? Short of removing and testing the pump, any diagnostics I can attempt. I'm going to start crawling through the FSM in between phone calls tomorrow... any suggestions would be appreciated. Thanks in advance!

 

[Skidoo]

Off chance, but check the electrical, fuses, relays, and that connectors are clean. Disconnect pump connector and meter it to see if power is getting to it.

 

[cruiseroutfit]

Off chance, but check the electrical, fuses, relays, and that connectors are clean. Disconnect pump connector and meter it to see if power is getting to it.

Thanks, those are on my hit list, I've not tried to unplug the brake booster pump but I'm assuming you can unplug it without removing the master assembly?

 

[cruiseroutfit]

12V @ the brake booster pump so it looks like 100% confirmation I need to replace or attempt to service the pump. All indications point towards the pump being non serviceable. So here is the conundrum, find a used pump or pony up for the new pump (~$950) and then rebuild the master cylinder (~$50) or I just swallow the pill and buy the complete assembly for ~$1800. Gonna sleep on it.

Other odd findings, the banjo bolt on the passenger side front brake caliper is leaking, I put a wrench on it and it was surprising loose? My guess is the shop that had this last was trying to bleed air out of the system?

I'm getting zero braking to the rear axle, lines and calipers look fine, pads have recently been replaced. I'm guessing the master cylinder has zero pressure headed to the rear. I didn't have much time to chase this down as I was buttoning up the park brake repair. The park brake is now working great, the bell cranks don't look to have been moving for a year or more? They were as seized as any I've torn apart over the years.

Any words of wisdom

 

[Copenhagen1]

My brother had this happen on his 99. He didn't have time or the inclination to fix so he put it in a shop. When they told him something like $2500 for the part he about passed out. He ordered a used one and required the shop to give his old one back. He told me that it was a case of the wires corroding at the pump and it was not able to get 12v. He said he repaired the original and has it on his shelf if it happens again.

I have posted this a couple times over the years so you have probably seen it in other searches.

Since I am reporting this third hand, would you like me to have my brother call you and tell you first hand what he did?

 

[100 TD]

Hi Kurt,

The motor draws approx 30-40 Amps IIRC, it is supplied power by 2 or more fuses (50A IIRC). I believe it has a failsafe circuit as part of the ABS circuit. In other words, the motor works off one fuse normally, and works of the other in ABS mode. On mine, 03/2003, I have a water leak(windscreen or roof rack) and occasionally the booster pump will start pumping for no reason continuously. (in normal mode a pressure switch should stop it) When this happens (once last year, twice this year) I pull the middle electrical connector on the booster module and the motor stops, ABS light stays on, BUT the braking system pumps up and works properly (without ABS).

When you turn on the IGN, you should get power to the pump for approx 20 secs, it may stop for a sec, then power again for a bit more until the pressure switch turns it off. Check all ABS fuses and relays
The fluid reservoir must not be filled up while there is pressure in the accumulator, otherwise it will overflow when it bleeds out of the accumulator into the reservoir.

If the motor went continuously it would burn out quickly as it's a short duration pump I expect. I would definitely see if I could lay my hands on a secondhand one for testing before shelling out the $BIG BUCK$

 

[cruiseroutfit]

My brother had this happen on his 99. He didn't have time or the inclination to fix so he put it in a shop. When they told him something like $2500 for the part he about passed out. He ordered a used one and required the shop to give his old one back. He told me that it was a case of the wires corroding at the pump and it was not able to get 12v. He said he repaired the original and has it on his shelf if it happens again...

I did read about your brothers experience, thanks for sharing that. Sadly the connections on my pump are clean and I'm getting a solid 12V to the pump. I wish I could confirm that the pump is non-serviceable short of tearing it down, time is precious this time of year and when I pull it I'd like to have the parts to put it back together but worse case I think I'll hurry and get it pulled and go from there.

...When you turn on the IGN, you should get power to the pump for approx 20 secs, it may stop for a sec, then power again for a bit more until the pressure switch turns it off. Check all ABS fuses and relays...

I'm yet to hear anything out of my pump but as noted I was able to confirm it has steady power. As its not building any pressure it never kicks the 12V to the pump off. Interestingly enough I did not that both the ABS MTR relays were clicking on and off in the fuse block while one is pushing the pedal. I'm assuming they were getting no pressure readings from the pressure sensor and trying to turn on and off to get pressure?

Thanks for chiming in guys!

 

[Skidoo]

I'm getting zero braking to the rear axle, lines and calipers look fine, pads have recently been replaced.
Any words of wisdom

The rear lines will not get any pressure without pump or charge in accumulator. The front lines will get some pressure w/o pump working, from pumping pedal.

 

[cruiseroutfit]

The rear lines will not get any pressure without pump or charge in accumulator. The front lines will get some pressure w/o pump working, from pumping pedal.

Excellent info. I honestly haven't done a think with it since we button the park brake back up and I planned to spend a fair amount of time with the FSM getting familiar with the system. Thanks!

 

[Skidoo]

Reminds me to mention: When your ABS/VSC lights up like a Christmas tree, you want to quickly evaluate the problem. If your pump failed you have 20 or so braking actions before accumulator charge is gone, at which point you will feel like Fred Flintstone trying to stop. If a brake line has blown you may have less (see spresso's post on blown brake line). Which is why it is a good idea to every so often check that your parking brake holds the vehicle in Drive at 1500RPM. You do not want to find out coming down Flint grade that your PB bellcranks are frozen with rust.

 

[cruiseroutfit]

Update, after sitting for a few months I was finally able to track down a new (used takeoff) master/ABS mod/brake booster pump and we finally had a free minute to install it this afternoon. Had to switch a couple parts from the old assembly (VSC switch plug was different) to the new setup but all is looking well. We did the best brake bleed you possibly can off vehicle and then again on vehicle w/o lines connected. We followed the brake bleeding procedure found here:
https://forum.ih8mud.com/100-series...quence-any-tips-you-can-give.html#post4330486

We now have good pressure to the rears (and no dash lights which is nice) but we are getting nothing to the fronts. I'm assuming its related to the ABS modulator not fully opening the ports and thus we need to get the front to activate? I had a chance to take it for a short drive and I don't have enough pedal 'push' to even get the fronts to start locking let along activate the ABS... the rears are activating nicely. We ran out of time tonight (had a club tech night building an Orion in the shop) but I'm planning to vacuum bleed the fronts tomorrow to see if that works?

Worst case I can run it down to the dealer and have them bleed it when hooked up to the SST, wondering if anyone has found a way to trick the ABS system into a 'full open' situation? Hoping there are some other suggestions?

 

[100 TD]

Had to switch a couple parts from the old assembly (VSC switch plug was different) to the new setup but all is looking well.

Something not right there Kurt, you should be able to bleed the fronts with heavy pedal pressure, even without the accumulator pressure or power/IGN on. In other words the fronts need to work without power or the pump motor working and without charge in the accumulator. (AFAIK)
What was the difference in the master cylinder besides the switch plug? Model numbers?
Correct lines in correct ports?
If your not getting pressure to the fronts Toyota won't be able to fix it AFAIK. Did you put a piston kit in it?
No dash lights means the motor is pumping the accumulator up to pressure (you can hear the motor run can't you?)

 

[cruiseroutfit]

Had Toyota do a full bleed on the system using their computer SST, brakes are great now but it definitely has warped rotors. We had a free minute in the shop to swap out the fronts today, rears tomorrow. From there I'm hoping my brake woes are gone with this rig.

 

[grundsethp]

I had the same issue and replaced the booster pump with some improvement but had various occasions where the 4 lamps and buzzer turned on. So I thought it might be a flaky electrical connection. I found my battery ground was loose ( my fault) but that did not help. I then read this post about the electrical connectors being corroded but they all looked ok...no visible green corrosion. I then took a close look at the pins on the abs module. I unplugged and replugged the connectors when the 4 lamps and buzzer were on and they turned off. So under close inspection, a couple of the pins where black and dirty. Uses some cleaner and qtips to clean and so far so good.




See the middle upper pin. It looks ok under quick inspection.