Vanwall

When my 2001 4runner sr5 starts up I can hear a pump priming up on the master cylinder/abs unit. How long should it do this? Sometimes it's brief 2 seconds sometimes longer 8-10 seconds. Is this normal? I purchased my yota in april of 07. It has always done this. The braking and abs/traction control system work perfectly I have no warning lights. My local dealer sucks!! they are reluctant to give any info when I call. Any info would be greatly appreciated.

eric-the-red

All 2001/2002 4Runner's do this, it's the brake booster pump you can hear. You may have noticed there is no vacuum booster on the master, instead they have an electric booster. The pump pressurizes the system, along with a cylinder of nitrogen. I don't fully understand it myself. You'll also notice the pump goes on when you brake.

GSGALLANT

It is perfectly normal. The pump pressurizes the volume tank. The pump is controlled by a pressure switch (you should be able to apply the brakes 5 or 6 times between the cycles of the pressurizing pump kicking on and off). Inside the volume tank is a bladder with nitrogen on the other side of the bladder. It works the same as the volume tank in a home water system (for those of you that aren't on city water), although home volume tanks would have air on the other side of the bladder instead of nitrogen.

When you apply the brakes, the assist comes from the energy build up in the fluid stored under pressure in the volume tank. It's a pain if you have to replace the system, because it's so expensive, but it's sort of nice because it gives you 4 or 5 reserve pumps of the brakes even if your vehicle shuts off when you're going down the highway at 80 miles per hour, as opposed to a vacuum booster which only allows one (maybe two) good assisted pumps of the brakes without the engine running.

Vanwall

thanx for the info that was what I was hoping to hear. synthetics all around and a timing belt where priority 1. next some blizzaks for winter.