At low revs, in heavy traffic, my brake pedal becomes solid as if my brakes are on & dragging?

Question

Vehicle is Toyota 4Runner 2002 model. Location is Santo Domingo in Dominican Republic. I have vacuum in the pipe from the engine to the servo. There does not appear to be a non return valve in that pipe, assuming it's in the Servo unit? In traffic the brakes are applying by themselves & floor pedal is at top & hard. Applying the brakes during this event causes wheel 'judder'? Once on the highway & at higher speeds the brake pedal returns to normal & braking is normal.
Am I right in assuming Servo unit is damaged?
What do I need to suggest for repair/replacement to local Toyota dealer?

Answer 1

Sounds like you need a serious brake inspection, first. Ask the dealer if he charges for this, as some brake repair places may not. If there is a shudder when you apply the brakes, its possible the brake calipers are sticking and this may be a sign of a more serious brake problem. Have your mechanic check for contamination of the brake fluid, sometimes if a different fluid is used, it will cause swelling of the rubber gasket under the cap at the master cylinder. If this is found, then you probably need to inspect the remainder of the brake system containing rubber,ie., the master cylinder, wheel cylinders, calipers, brake hoses, brake equalizer, etc. Good Luck, if you need more answers e-mail me back.

Answer 2

Not sure about your ride, but some servos make the pedal feel hard when there's no vacuum to them, so low vacuum at low engine speed can do that. A leak or worn out rings.

Answer 3

your braking action or a bad master cylinder that is causing this. it like pumping the brakes up. be conscious to take your foot all the way off brake after stopping so that the master cylinder can relieve the pressure build up. if this doesn't solve it check the brake system over for binds, kinks and etc..

Answer 4

time for a new servo /booster

Answer 5

have them to check the roters, and calibers.