Horrible brakes !!

[MudbogPete]

My 97 has about the worst brakes of any vehicle I have ever driven.

I didn't realize it during normal driving, but I had to do a panic stop yesterday and the initial hit on the pedal greeted me with a lot of resistance before the pedal traveled enough to get the brakes to bite. It took probably 1 second before full braking was in force....way too long!! Even when the brakes were grabbing, it was not anywhere near the edge of lock up. This vehicle is very unsafe in a panic situation.

The impression that I get is, the vacuum boost for the power brakes can not respond quick enough in a panic stop. Using the brakes slowly as in normal driving, the feel is very powerful as it should be, but when you have to respond fast, the unit is not up to the task. I wonder how often brake booster go bad ?

The pads are in excellent condition. The pedal travels more than an inch ....probably closer to two inches before the brakes even begin to engage. If I pump the pedal once, the distance is cut in half. This says that perhaps the master cylinder is worn ?? ...or maybe I have a little bit of air in line ?

Has anyone else here checked to see how quick you can scrub off speed in a panic stop situation ? If not, I would advise you try it and see what your results are... I would be interested to hear if anyone else has the same symptoms as I do.

 

[thunderpaw]

The brakes on our '97 4runner are great, better than most cars.

I haven't been able to engage the ABS yet though - since I drive race cars it is very difficult for me to lock the wheels long enough that ABS figures it out - I bring the tires to the edge and can stop more efficiently than ABS anyway.
When I've tested the brakes on the 4runner, it's been able to stop quickly and efficiently and no pulling. It's no sports car but it's definitely a Toyota!

First off, I would check your fluid - if it's brown flush it all out. You say pads are fine so that's good. If the fluid is good, just bleed 'em and see if you get any air out.

It's possible your vacuum assist is dead/dying. Check the various hoses/etc make sure they're in good shape.

Also the master cylinder could need replacing, has it ever been replaced? On street vehicles I like to replace them every 5 years or so even if they seem to be in good shape.

Also, check the lines at the brakes, are they worn needing replacing? They might be expanding under pressure - causing a delay before the pistons move and also causing the pedal to go down more than you think it should.

 

[MudbogPete]

Thanks for the feedback.

I think a good starting point is to replace the master cylinder and purge the brake fluid. If the problem still persists, I guess I could check the booster for leaks and then replace it if I don't find any leaks. It is kind of expensive, but not worth a crash if I can't stop due to lack luster brakes.

 

[jharris2]

Before you flush everything out, try bleeding the lines first. If air somehow got into the lines, you'll have a very tough time stopping.

Also check the discs (and drums, if you have them) to make sure they are not gouged out or scarred.

Reason I say this: I had a Mustang many years ago that had no symptoms of brake failure until the brake pedal went to the floor one day after stopping at a light. Turns out the front pads were worn past the rivets all the way to the plate -- what was left of the pads was about the thickness of a sheet of paper. The rivets had gouged out a channel on the discs.