LV_4Runner

1997 4Runner SR5 4WD A/T 113k miles.

Actually, my brake has been a little weak ever since local dealer did something on my brake system back in 1999. I had the front rotors warped (very typical problem) that time and then, local dealer re-surfaced. After that, it did not feel like the original braking anymore.

I initially thought that it may be because of re-surfacing but, about 15k miles later, I replaced the rotors with brand new OEM rotors completely. yet I couldn't restore the original braking anymore. Since then, it is really really really slowly getting worse and thesedays, I really need to pay attention to my right foot to stop the car. meaning I really have to strongly hold my brake pedal with my right foot...

In other words, as I am gradually pushing brake pedal, it does not linearly or gradually stop the car, rather when the brake pedal reaches to its limit, the braking force suddenly went up then car stops.... In other words, it is rather a little difficult to control braking force....

What could be the cause of this one?

The front rotor is good, pad is sufficient and I do NOT think rear brake shoe has much to do with this. No interesting noise or anything! I do NOT think it is master cylinder either as it breaks, anybody will notice such sensational feeling possibly with some cold sweat (or maybe even pees on pants... )

Anyone?

lee

have a friend push the brake while you perch your head underneath, by the front wheels... do you see a leak?

Unhappy99

Does the pedal go down too far? How about if you give it a pump or two, then try to brake normally?

1) Ensure you are not leaking fluid anywhere.
2) Test the master cylinder in your driveway with the engine off. Pump the pedal once or twice, then push the pedal firmly. Does the pedal slowly creep down, or stay put?
3) If your fluid is more than a few years old, flush the brake fluid and properly bleed the lines.
4) Change pads to a ceramic material.

rimpainter.com

Wait, the pedal goes all the way to the floor before the vehicle stops?

LV_4Runner

thanks a lot of your prompt response.

The pedal seems going to deep down to make the car stop.

However, I am pretty positive about my master cylinder as it stays firm after a few pumping with ignition off. (I actually had two times of experience with faulty aged master cylinder on my other 2 cars, I know how it feels...)

No leaking underneath.

And the pad and rotors that I replaced a few years ago was the famouse one ,which is Autozone #5024 for a 96 LandCruiser and rotors are brand new oem. Thus, I am positive about brake pad too....

Brake oil has been a few years but when I replaced it a few years ago, it didn't improve.

Any other idea? Could it be booster? I do NOT know what is the symptom of faulty booster....
or could it be pedal adjustment? anybody has any idea?

celica

check you vacuum line heading to the booster for leaks, cracking, plugged, etc.

rimpainter.com

With the vehicle running, pump the brake a few times and hold. If it sinks to the floor your MC is shot (or you have air in the lines or a fluid leak).

ebelen1

Hopefully, this is not noise but if you deem so, just ignore.

I also have a 3rd gen and it seemed like I had to pump the crap out of the brakes to get the truck to stop from high speeds or just let momentum stop the truck after slowing it down before an intersection. I had 98k miles on the OEM pads and they were worn. The stock rotor had not been turned and was slightly warped.

I decided to do the Tundra brake upgrade and the difference is night and day. I step on the brakes from high speeds and the truck stops (I even have more cushion if I needed to stop faster.) When I get to an intersection, I step on the pedal and the truck stops. I don't need slowing momentum to stop.

If everything else is OK (master cylinder, brake fluid, etc.), consider this upgrade. It was definitely worth it for me...

LV_4Runner

Thank you for all this reply.

Again, I do NOT think it is MC again, I had two of MC shot experience, the feeling of sinking brake pedal is quite evident and scary... nothing like one needs special attention to notice...

I will look into booster line first as "celica" suggested.

Then, if that does NOT solve, I may consider brake upgrade. BTW, how much is that upgrade? where to find the parts etc?

Unhappy99

If you pump the pedal once and then quickly apply solid brake pressure, does the pedal feel improve? If so, its not the booster. If the pedal goes deep, then you either have air in the lines, warped rotors, or misadjusted rear shoes, or a combination of the three.

Air in the lines causes a spongy pedal feel and requires more pedal travel.

Warped rotors will push the pads off the rotor surface too far, so that when you go to brake, you need more fluid, and therefore more pedal travel, before contact with the rotor is made.

Misadjusted rear brakes means that more fluid will be required before the rear shoes make contact, resulting in longer pedal travel.

ebelen1

The upgrade consists of new rotors and calipers. The cost between Tundra rotors and 4runner rotors is minimal, if you were getting new rotors that is. I used Brembo slotted and they cost me $150. You can also use OEM and I do not have price info on them.

I used Raybestos fully-loaded calipers and I think these were $90 a piece, plus core charge, which you get back once you give them your old ones. The cool thing about these rotors is they came w/ semi-metallic pads and they come in a cool powder-coated gun metal color. My rotors and calipers under my wheels look awesome. When I get back home, I can get a couple of pics for you. Also, if you do decide to do this, I can search for the Raybestos part numbers as well.