The pedal should go soft as you describe somewhere before the 40th pump. 30 is fine. I don't think it makes any difference if you go beyond that once you notice it go soft, but finishing up to 40 doesn't hurt anything. It is at that point that you set the reservoir to the max line.
Master Cylinder Rebuild - DIY (2 Viewers)
- Thread starter Skidoo
- Start date
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2001LC
SILVER Star
Once you've finished the topping procedure and topped the reservoir to max line. Turn on the IG key (don't start) and time how long booster motor runs. Spec is 30 to 40 seconds. Over that indicates air in the system that needs bleeding out or a leak.
So I pumped the brakes 40x and recorded the time it took to pressurize and it took 36s and 37s the two times I did it. I did notice, however, a drop forming below the cylinder looking things left of the reservoir (when facing it). How would it be pressurizing in the right amount of time and still have a leak? I'm hoping a brake line just needs to be tightened.
Thoughts?
And thank you all for the help.
Thoughts?
And thank you all for the help.
2001LC
SILVER Star
If leak before pressure side of system.
You should be able to find some area that is wet with brake fluid on the master assembly. Then clean really good and try to pin point.
You should be able to find some area that is wet with brake fluid on the master assembly. Then clean really good and try to pin point.
2001LC
SILVER Star
I believe it to be (not yet torn apart to confirm) HP line from pump/accumulator to master cylinder chamber. This is a spot that may or may not reveal itself during the timing test (leak) of booster motor 30 to 40 sec. I say may or may not as the Toyota training manually doesn't give us specific, only general braking system info. So you could leak from it or the flare nut fitting at either end, and "may" still come in under 40 seconds. But I've never seen one leak. As generally these flares only leak if removed. They are not removed unless accumulator pump assembly replaced.
If you think you've a leak there. Snug the flare nut just a tad. But more likely a reservoir grommet(s) or the #2 hose.
If you think you've a leak there. Snug the flare nut just a tad. But more likely a reservoir grommet(s) or the #2 hose.
Last edited:
- Thread starter
- #287
Carefully tighten the ends of that red tube.
Might set up a smartphone or small camera to take a video of where you think the leak is, to see what is going on.
Might set up a smartphone or small camera to take a video of where you think the leak is, to see what is going on.
2001LC
SILVER Star
I've not. But it's been reported in mud more than once.
Checking up on this thread, per 2001LC 's suggestion, i should try to rebuild the MC for my buddy, this 04 LC is making this squealing noise, and air is coming through. There's no loss in brake pressure or spongy feeling though, hopefully rebuilding will fix this issue.
uHu
Bridgeburner
FX: When does the squeal occur?
uHu
Bridgeburner
Might be the valve for the booster accumulator. I would try s thorough bleeding, after letting all the pressure out of the accumulator, in order to exchange as much of the fluid as possible. And use Toyota fluid.
I bought the MC rebuild kit for him, i'm going to do it this weekend and bleed the brakes at all 4 corners and see if it'll cure it, everything works just something is leaking and letting air through the reservoir.
Thanks @Skidoo for the writeup and thanks @2001LC for the diagnosis. I repaired/rebuilt my buddy's MC today, turns out the plastic thing before the o-ring broke apart, not sure if that's what caused the air leak or not but the new piston kit seems to have fixed the issue for now. At first after bleeding, there were still that crow noise, but after a few cycles it had stopped. I tested it by pumping the pedal with engine off to depressurize it then turn the engine back on, it would build pressure then stop. Before it would just keep pumping and pumping until the alarm went off, brakes still acted fine though but the alarm and the screeching noise wouldn't stop. It's all good now. On the 2004 LX, there's no evap canister in the way but the VGRS column blocks 2 of the bolts that holds the MC unit, you gotta feel around back there to get to it with a ratcheting 12mm combo wrench.
To prebleed it, after putting the new piston in, pour fresh fluid into the reservoir and push the piston in a few times until no air bubbles come out of the 4 brake lines port, when it shoots out constant fluid then you can put the unit back in. After that, I turned the key on, let the pressure build until it's maxed out then i bled the passenger rear brakes, driver's rear brakes, passenger front brakes, then driver's front brakes. Charged him $200 for the job, took me about 2 hours from start to finish, seems fair? Better than a couple grand to buy a whole new unit which we thought was the route.
To prebleed it, after putting the new piston in, pour fresh fluid into the reservoir and push the piston in a few times until no air bubbles come out of the 4 brake lines port, when it shoots out constant fluid then you can put the unit back in. After that, I turned the key on, let the pressure build until it's maxed out then i bled the passenger rear brakes, driver's rear brakes, passenger front brakes, then driver's front brakes. Charged him $200 for the job, took me about 2 hours from start to finish, seems fair? Better than a couple grand to buy a whole new unit which we thought was the route.
2001LC
SILVER Star
The angled slit in white plastics ring is as designed and not a break.
Sometimes you just can't see anything wrong, but R&R does the job.
Sometimes you just can't see anything wrong, but R&R does the job.
learned something new everyday
2001LC
SILVER Star
I learned BG has brake fluid. First time I've seen!
My brakes are fine however I ust drove my cousins LX470 and his stops way qiucker than mine - Mine requires alot more travel to get the same amount of stopping. I kept accidently slamming the brakes because i was used to needing to press 75-90% down to stop.
Woudl the rebuild kit help this?
Woudl the rebuild kit help this?
