Heavy Brake Fluid Leak

[MTNRig]

So I've searched the forum for several weeks now and am still stumped as to what may be causing a steady brake fluid leak in my 2000 LC. It happened after I suddenly hit the brakes in traffic. It wasn't overly hard, but just sudden enough to get me and my passengers attention. Anyways, the next morning I noticed a significant puddle on the ground coming from the front driver's side inside fender. I did a little snooping around and noticed a steady leak appearing to come above the brake booster, under the reservoir, and under the abs box. Unfortunately, I can't get an angle to see where exactly the leak is coming from, short of removing the entire master cylinder, accumulator, booster, disconnecting the lines, etc. Anybody else ever have this problem? Anyone know what the culprit(s) may be? Just looking for some advice before I tear into it. FYI...no abs lights or buzzers have gone off and I pumped the pedal 40 times then started the vehicle. I heard the pump running and then noticed and VERY steady leak. The leak doesn't seem to occur unless the vehicle is running.

 

[Sandroad]

Here are couple of threads from a quick search. See if these help? I wonder if the sudden stop loosened the seal mentioned in these threads and the jiggling when driving makes it worse?


Brake fluid leak from reservoir?


https://forum.ih8mud.com/threads/brake-fluid-leak-from-did-i-make-a-problem.902309/#post-10127161

 

[Daskoff]

So I've searched the forum for several weeks now and am still stumped as to what may be causing a steady brake fluid leak in my 2000 LC. It happened after I suddenly hit the brakes in traffic. It wasn't overly hard, but just sudden enough to get me and my passengers attention. Anyways, the next morning I noticed a significant puddle on the ground coming from the front driver's side inside fender. I did a little snooping around and noticed a steady leak appearing to come above the brake booster, under the reservoir, and under the abs box. Unfortunately, I can't get an angle to see where exactly the leak is coming from, short of removing the entire master cylinder, accumulator, booster, disconnecting the lines, etc. Anybody else ever have this problem? Anyone know what the culprit(s) may be? Just looking for some advice before I tear into it. FYI...no abs lights or buzzers have gone off and I pumped the pedal 40 times then started the vehicle. I heard the pump running and then noticed and VERY steady leak. The leak doesn't seem to occur unless the vehicle is running.

Interesting....I have the same issue I think, but I have not verified it is coming from booster. I picked up my truck from my mechanic who did a complete brake job, pads, rotors, and Slee SS lines. Next morning I noticed a puddle under the left front drivers side. I could not see where the leak was coming from so upon further inspection I noticed that the brake fluid reservoir was filled to the cap. I used a turkey baster to bring it down to the max line and went for about an hour drive. Checked the brake fluid level and it dropped from the max line down to about the mid point between max and min. I put some cardboard under the affected area and I checked last night and no leak. It's driving me crazy - I will be taking it back to the mechanic and asking him to check the brake booster as well and let you know what I find. The only thing I can think of is that he used air pressure to bleed the brake which may have ruptured something in the booster? besides the hard stop have you bleed the brakes with air pressure assist? I can't imagine that a hard stop would damage the booster...it should hold up under much more intense braking as in emergency situations.

 

[Daskoff]

Here are couple of threads from a quick search. See if these help? I wonder if the sudden stop loosened the seal mentioned in these threads and the jiggling when driving makes it worse?


Brake fluid leak from reservoir?


https://forum.ih8mud.com/threads/brake-fluid-leak-from-did-i-make-a-problem.902309/#post-10127161

Dang - I should have read this first....Looks like this is exactly what happened (first link above) to me.........

 

[Bardiya]

Had the same problem many years ago, I think the entire booster assembly was replaced but I'm not sure.
I will check the paperwork when i can

 

[MTNRig]

Here are couple of threads from a quick search. See if these help? I wonder if the sudden stop loosened the seal mentioned in these threads and the jiggling when driving makes it worse?


Brake fluid leak from reservoir?


https://forum.ih8mud.com/threads/brake-fluid-leak-from-did-i-make-a-problem.902309/#post-10127161

Thanks. I had already previously searched these threads and I'm not sure if they relate to my exact problem. The interesting thing about this leak is that it is a very steady drip (about 1 drop per second) that occurs only when the vehicle is running or shortly thereafter, so I'm not sure if it's coming from the reservoir. I haven't noticed anything coming through the firewall, as is the case with many master cylinder failures, so I think I can eliminate that as the issue? And I haven't had any brake work done recently, so I can rule out improper bleeding or overfilling the reservoir by my mechanic. I'm stumped. Anyways, I appreciate the feedback and have scheduled an appointment with my mechanic tomorrow. I'll post up whatever he figures out and let you all know. Thanks!

 

[sean2202]

I created one of those threads. There are rubber o rings under the master cylinder that have to be replaced on mine. It was overfilled at the Toyota dealer in the winter and that is when my problem started. It has been OK now in the warmer weather but believe those seals have worn out. It is on my list to do before winter. Same situation all of a sudden a drip, no loss in braking pedal, I pumped the hell out of it and beaked hard to see if I would lose pedal and have not.

 

[MTNRig]

Update: So I just heard back from my mechanic. He informed me that he believes the leak is coming from the ABS ECU. I think he may be confusing the brake booster with the ECU because what I surmise from the FSM is that the ABS ECU is located on the interior of the vehicle near the brake pedal and that is definitely not where the leak is coming from. He was hesitant to tear into and recommended that I take it to the dealer. I still suspect the leak may be coming from the booster itself. Is anybody aware or any lines running to or from the booster that may be the culprit? Actuator hose, actuator tube, maybe a grommet from the reservoir? All components still seem to be operating well, just an extreme leak that I can't seem to pinpoint.

 

[sean2202]

Take your finger or a paper towel and rub it under your master cylinder reservoir. Keep tracing it down until you find the leak. I can understand why you are having trouble as it took me a long time to locate mine. It will drip down on the abs moduale so it can look like it is coming from there. Are you pumping 30 times before adding fluid each time? Remember brake fluid takes off paint.

 

[MTNRig]

Okay, after a few days of calling around and looking for any more details regarding a proper diagnosis, I have finally determined that the leak is coming from any number of the solenoid valves inside the abs unit. Being that every mechanic I've spoken to has refused to attempt to fix the issue based on Toyota's determination that the brake assembly unit is considered "non-serviceable", my only option left is to replace the entire unit. So I bit the bullet and ordered the entire assembly from @beno. I plan on doing the install later this week with the help of a friend and MUD, as the removal and replacement of the unit seems pretty straight forward. When I replace the unit I plan on bringing it to the dealership for a full bleed since that appears to be beyond my level of expertise, at this time. My question is, am I safe driving it to the dealership or should I hedge my bets and have it towed instead? If it's okay to drive, is there any specific procedure that I need to follow regarding pumping the brakes, leaving the reservoir cap off, etc. before starting it or driving it?

 

[MTNRig]

Installed the new assembly today. Straightforward with no hiccups. Haven't had a chance to tear apart the old one to find out exactly where the leak was coming from. Anyways, no ABS light, no brake light, no buzzers... Just a soft pedal for now. Will be driving it the short distance to the dealer next week for a full bleed. Can't wait to get this rig back in action, the mountains and rivers are calling!