The brakes on my 00 4Runner are not working too well. You can slam on the brakes at speed and it stops pretty well, but not good enough to activate the anti-lock system. It's definitely not up to par for towing. It'll barely stop my boat on a slight incline. The pedal seems to have decent resistance and it doesn't go to the floor or anything like that. Rotors/pads are fine.

I had no idea how old the current fluid might be, so I got smc to flush them with new fluid. They're still not working very well though. Is there anything else I need to check or should I go ahead and put a new master cylinder on there? Is there a way to test the master cylinder before dropping $200 on a new part?

[Edited on June 14, 2010 at 6:21 PM. Reason : l]

6/14/2010 6:17:40 PM

Did you check the surfaces of the pads/rotors closely? Look for tiny stress cracks on the rotor and see if the surface of the pads has a smooth glazed look to it.

[Edited on June 14, 2010 at 7:06 PM. Reason : How heavy is the boat?]

6/14/2010 7:05:25 PM

I'm guessing rear axle seals are leaking diff oil onto your rear brake shoes; look at the edge of the backplate/drums from underneath the car and see if you've got oil splatter on the inside of your rims or heavy oil residue/drops dropping from the bottom edge.

If so, welcome to the club. It's a common issue on all 3rd gen 4Runners which can lead to loss of rear brakes, inoperable (slipping) e-brake, and excessive heat/wear on the front rotors that can warp them, and obviously poor stopping power. Let us know what you find.

6/14/2010 7:42:58 PM

Quote :

"I'm guessing rear axle seals are leaking diff oil onto your rear brake shoes; look at the edge of the backplate/drums from underneath the car and see if you've got oil splatter on the inside of your rims or heavy oil residue/drops dropping from the bottom edge. If so, welcome to the club."

Nah...Already had that issue over a year ago. Jeepman put in a new axle seal for me. I highly recommend him if you need the job done and he is still doing side work. I've replaced the rear rotors since then.

^^ I'll look closer tomorrow in the light. Can't see much right now. The boat is probably 3200 lbs on the trailer and I could barely get it to stop from 20 MPH on a slight incline.

[Edited on June 14, 2010 at 9:04 PM. Reason : l]

6/14/2010 8:35:04 PM

It all looked pretty dry to me. I might have sprayed a little brake fluid on the axle when I bled them, but what you'd be looking for is fluid in the drum itself from the axle ends.

It may just be a glazing issue that a new set of pads and sanding the rotors would correct.

6/14/2010 9:57:21 PM

My outer seals were the leaky ones so lucky me out in the sticks I had to get a machine shop to remove and just put on new bearing$ while I was at it. Worn bearings or even slight quality irregularities can still let the oil seep past one or both new seals on each side. IMHO, I wouldn't cross it off until I took the drum off, or do you have the all wheel disc conversion?

If not that or glazing, I'm thinking it might be remaining air in the lines or leaky brake booster.

[Edited on June 15, 2010 at 11:39 PM. Reason : .]

6/15/2010 11:37:01 PM

Brake fluid isn't leaking. If it were the master cylinder wouldn't have been full when I first checked it. It was literally at the top of the fill line...Right where I left it a year ago when I bled the brakes after replacing a bad brake line.

I'm pretty sure it's not air in the lines. Seems like that would have been there for at least a year and I would have noticed it a long time ago. Also, smc bled the brakes with new fluid on Monday and the issue is still there. Usually when I've had air in the lines I can get the pedal to go to the floor. This is different. It feels firm, but no matter how hard you press the truck just doesn't stop very well.

I feel confident my rear axle isn't leaking. With 75% of the braking being done on the front rotors I really doubt a leaking rear axle is going to make that big of a difference anyway. I should still be able to lock it up and engage abs with the front rotors alone.

Didn't get a chance to check the rotors for glazing/cracks today. I should have some time tomorrow to look at it.

[Edited on June 16, 2010 at 1:46 AM. Reason : s]

6/16/2010 1:44:32 AM