wiseguymmiv

Today I pressed down harder than normal on my brakes while stopped at a red light. The brakes stop the 4Runner just fine, but when I press down hard while stopped, I feel a vibration in the brake pedal and hear a rubbing noise, sort of like rubber or plastic rubbing together. If I don't press down hard, the brakes work fine, and I don't hear or feel the rubbing problem. I've only done this while sitting still, but at every red light I tried this, it happened again. The pitch of the rubbing sound changes the harder I press on the brakes. Since I'm not moving when the sound occurs, I don't think this is a rotor/ brake pads issue. What could this be? I had my power steering pump changed a few weeks ago due to a leak, but don't belive that affects the brakes. Any ideas?

tried4x2signN

My guess is the rear ABS...

yotaman85

when you press on the brake pedal real hard it puts a strain on your pump, your belt is slipping, the harder you push the mare it slips, hence the change in sound.. now this is completely a hypothesis and should not be put in stone.

24Runna

Did you put a custom intake on?
That will rub and you will feel it.

Yotaman, IIRC there is no belt for the brakes?

yotaman85

uhhh, wow. I know, total brain fart...i feel stupid now...

wiseguymmiv

Nope, the intake is original. Any other ideas?

BigBluePile

iTrader: (3)

Does it only do this with the motor running? Brake booster...?

tried4x2signN

what's that thing a Toyota 4Runner or V6 has that's on the frame, right between the motor and battery?

is it the LSPV?

wiseguymmiv

BigBluePile, I'll try it with the motor off tomorrow and post the outcome.

tried4x2signn, I had to look up the definition of "LSPV," so I'm no help on that question.

For those of you like me who aren't familiar with the LSPV, that's the Load Sensing Proportioning Valve, which "is designed to compensate for the payload a truck is carrying by sending the appropriate amount of fluid pressure to the rear brakes (the goal is to deliver maximum stopping power without causing the rear tires to skid and lose traction). The LSPV uses a mechanical linkage to determine ride height/payload (system assumes that an empty truck is going to ride higher than a full one)." http://www.off-road.com/trucks4x4/ar....jsp?id=186295

Now that I read that article about new shocks requiring a bypass of the LSPV, I should note that I had new shocks put on the Yota when my power steering pump was changed a few weeks ago. However, my ride height didn't increase much, if at all. I added no lift, just new shocks. I believe they are Monroe Sensa-trac shocks. Could that have caused this problem? Seems unlikely, but then again this problem never occurred before I put the new shocks on.

wiseguymmiv

BigBluePile, the brake issue doesn't occur with the motor off. It also doesn't occur every time I press on the brakes.

wiseguymmiv

Well, the plot thickens... I took my 4Runner to my local, retired shade tree (but Toyota-certified) mechanic with the brake rubbing/vibration problem. He did some tests, and noticed the problem I was complaining of, but couldn't determine what is causing the problem. It could be a vacuum issue, but that's just a guess. He said he rather not guess, as he could be wrong and would be wasting my $$$. So, I took it to the Toyota stealership and described the problem. Hours later, they tell me I need $2,646 worth of work to correct the problem. Brake pads, new rotors (the Brembos and pads are only 3 or 4 years old), new master cylinder, new brake booster, adjusting and cleaning the rear brakes, a ball joint replacement, and an alignment. My 4Runner drives just fine, except for the occasional brake rubbing/vibration.

Their $2646 fix-it list was complied, because they didn't want to be honest and say that they didn't know what was causing the problem. This is the shotgun approach- replace everything and the problem is bound to be fixed.

Bluebook price on my 4Runner- $4,065.

I've had bad experiences in the past with this dealership, (claiming I needed a$2000 + rear end job from not "changing rear end fluid", when a $300 wheel bearing replacement by a 4x4 shop solved the problem) but thought I'd give them a shot at figuring out the problem, since that past issue arose several years ago.

So, what do I do now? I'm not going to pay Toyota to do this work, because I don't believe all of that is necessary. I'm going to pull the wheels off and check the rotors and pads myself. Anything else I can test or check?

Question 2: What happens if a ball joint fails? What about the brake booster or master cylinder?

Blue_petersen77

Where exactly is the noise coming from?

wiseguymmiv

It's coming from the engine compartment. Maybe I can have a friend press the brake tomorrow while I listen under the hood to pinpoint it.