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Discussion Starter #1
My back left brake locks and ABS doesn't kick in. Any ideas? I've bled the hell out of the lines but no luck.
Back left kick out and tries to kill you in an emergency brake situation from 20 mph up. Fine under normal breaking however.
 

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Probly the pistons in that caliper are sticking or rusted
 
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They are all brand new and it didn't fix the problem.
Well damn. There is a guy named FJtest on here He seems to be a a hell of a problem solver. Wait for him to chime in :)
 

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You didn't provide any background information like model year, odometer reading, or geographic location, but when servicing the rear calipers, were the parking brakes also disassembled, cleaned and inspected?

Are any system warning lights illuminated on the instrument panel?
 

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Discussion Starter #6
Thanks FJ test, good questions.
  • 08 at, 160k, Seattle
  • Parking brake was not services but did just adjust them as we were in there today anyway. But problem was the same before and after
  • No warning lights other then when the abs and TC lights came on during braking. Yes the TC lights came on when it starts to skid.
Other stuff.
  • No codes. Did have some a few weeks ago but the brake light sensor took care of those and they didn't come back
  • Back left and front right don't bleed right. Pump sometimes doesn't come on at first stab. Or need to wait.
  • Sometimes the problem goes away if you do a few emergency brakes in a row.
  • Their was a ton of air in the line after redoing the caliber etc, but we did everything we could and went through 4qt today. Did it the traditional way a few times then did it by Toyota tech book by the letter with 100 second bleeds in the rear and all. When we did that the back left would stay pumping the entire time, and had to go back to old school pump and hold until it stopped.
Thanks!
Lastly I have scheduled to go to a dealer Tuesday to see what they can find. A too of the line snap on reader was on it today however. Read somewhere that the Toyota techs can do the bleeds from their readers.
 

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Discussion Starter #7
So dealer says it is because of aftermarket pads and rotors and that you can't bleed them right unless you are at the dealership.
They are the cheap Brembo rotors and pads, but sure seems odd. They said the pads are chipping
What do you think crew and @FJtest
They also think it could be the booster but wants to try this first
 

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Discussion Starter #9
Hope it’s not the booster, $$$$$$

I’m interested in hearing what fixes this.
Thanks got them to admit the pads and rotors were not causing the issue just something they reccomend. (They are beat to hell cause I've brake checked this thing so many times trying to figure it out. They are 3 months old as well as the calipers)

I'm gonna have them use their tool to bleed it and see what happens. Right now they say it might just be the booster and not master cylinder which would save some dollars.

The funny thing is I had a 7:30 am appointment today and they took all day to tell me this so now can't bleed until tomorrow. Thank God for COVID and not needing a car
 

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You can bleed your own brakes.

 

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So dealer says it is because of aftermarket pads and rotors and that you can't bleed them right unless you are at the dealership.
They are the cheap Brembo rotors and pads, but sure seems odd. They said the pads are chipping
What do you think crew and @FJtest
They also think it could be the booster but wants to try this first
Any statement that the hydraulic system cannot be bled because of the brand of pad or rotor is complete BS, assuming that the parts are correct for the application and the pads are not somehow binding in the caliper.

Not sure I understand your statement about the new pads "being beat to hell" because you have done multiple hard stops. Please explain what 'beat to hell' means ... what's the appearance of the pads? Have you seen this "chipping" the dealer referred to? This is clearly NOT normal for any pad, so this may be a clue to some type of problem with the pads, calipers, or rotors.

Are you sure all the wheel speed sensors are undamaged? Have you pulled them and looked for debris or damage on the nose of the sensors? This is quick and easy check, along with a meticulous inspection of the sensor cables and connectors.

I suspect the ABS system is the culprit ... you say the left-rear wheel locks during braking.

During hard braking, much of the vehicle's weight is transferred to the front wheels, so if the front tires have traction, they will not lock.

However, the opposite happens at the rear wheels. During hard braking, the weight transfer unloads the rear wheels, and they are inclined to lock up first. If the ABS is working, it will trigger at the first hint of wheel lock, and release hydraulic pressure as required to prevent full lockup. But if the ABS on the left rear wheel is NOT working properly, that wheel alone will lock up. Normally, you will see a fault code if an ABS sensor is circuit is open or shorted, but you say you are seeing no codes.

During braking severe enough to lock up the left-rear wheel, does the ABS trigger on the right-rear wheel??
 

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Discussion Starter #13
@FJtest You rock.
Sorry I don't know if the pads "are beat to hell" All I know is I have done more emergency braking in the past three months since I installed these pads, rotors, and calipers they have been through a lot. Probably more than when I take my BMW to the track. They didn't show me the chipping and I haven't looked. Also, they said the rotors needed to be resurfaced because they were glazed... Also when I bought this thing the rotors were so warped I never really did an emergency brake test before I put the new rotors in. Makes me think the guy selling it was covering this up maybe?

Haven't checked the sensors as I thought they would throw a code, but might replace them as they are cheap enough and easy enough to install and I don't think I have the tools to inspect them.

As for what happens during emergency braking the back left locks up almost immediately, then the rear end swerves left and front right. Then the traction control comes on and beeps like hell. The only time I can get ABS light to come on is in the gravel under the same situation. Actually have more luck with the back not locking up in the gravel, but still does on occasion. Say 70% on gravel and 99% on the street. Sometimes if I do enough checks the system seems to work and I brake straight.

Mechanic friend that helped me over the weekend also said "There was a difference in pressure in the left rear than the others. It wouldn't activate the pump and it doesn't release under abs activation."

They think it is the booster if it isn't air in the line. If I do the sensors and it still happens can I just replace the booster and not the master cylinder as well? If so do I need to have the Toyota machine to bleed at that point?

Also doesn't seem like it would be the booster if an ABS problem, but I'm a Youtube mechanic which means I am not a mechanic...
 

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Same problem with right front for years. Finally solved by local brake shop by replacing brake line on that side.
 
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