Odd Noise in 01 4Runner..

[jim4runnerny]

I have a '01 4Runner (sport, 4WD) with 60000 miles and lately have been hearing an odd noise that I'd like all of your opinions on it before I have the dealer take a look.. Here we go..

The sound is coming from the passenger footwell/firewall area.. it occurs pretty consistantly whether or not the engine it hot or cold... the sound sounds like a hissing for a few moments which is then followed by a click.. It seems to happen when I slow to a stop.. the hissing will start when I am driving and just as the car rolls to a stop I hear the click.. To me it sounds like some sort of pump that is building up pressure and then clicks off (relay or solenoid opening/closing).. could this be a faulty fuel pump?? Something to do with the ABS/ATRAC/VSC systems?? Other than the sound, the truck seems to run fine.

Any thoughts, or is this normal? I'd hate to take it to the dealer without giving the some sort of hint (I am still under the certified warranty).. Thank you in advance!!

Jim
Pittsburgh, PA

 

[kvanderploeg]

My '01 does it too. I always just figured it was the washer fluid pump pushing fluid to the back of the truck for the rear washer. I could be wrong...it's happened before.

Kent

 

[GSGALLANT]

That sound is normal. The 2001 and 2002 4Runners have a hydraulic brake booster instead of a vacuum brake booster. There is a small pump/motor unit that pulls brake fluid from the reservoir, and pumps it into an accumulator to keep it under pressure.

This "pressurized" section of brake fluid is what helps you apply your brakes. Everytime you press the brake pedal, a small amount of this "pressurized" fluid moves into your master cylinder and brake lines. When you release the brakes, the excess fluid returns to the reservoir. After applying the brakes a few times (4 to 6), there is a pressure switch that detects low pressure in the accumulator, so the booster pump kicks on (The whirring sound). When the pressure is back to normal, the pressure switch shuts the pump off. (I think the passenger side clicking is the relay snapping off).

With the truck running and in park, depress the brake pedal, then release it, wait a second, depress the brake pedal, then release it (repeat this 5 or 6 times). You should hear the "whirrrrrrrrrr-click." every 5 or 6 times you hit the brakes.

 

[kvanderploeg]

That makes even more sense than my answer! :

Thanks GSGALLANT!

Kent

 

[jim4runnerny]

Hey, thanks for you help!! I figured it might be normal, and I do notice it more now that my commute is a lot of stop and go traffic.

Jim

 

[polvadis]

I have that noise, too. And I must say it's really annoying. Maybe not so much the hissing sound but the relay turning it off is pretty loud. I don't think I heard it before, and now it's always there.

Maybe it's something that needs to be looked at by the dealer? I'm almost willing to find out myself, but the local guys cost $75 bucks to get a diagnostic done, and that might not do the trick, so money wasted...


By the way, I also had a Thread going about this noise a few weeks back.

Here's the link

 

[eddiekillz]

I'm so glad I found this bulletin. I just recently bought a used 2001 sr5 runner. I kept hearing this sound when I came to a stop and thought something had to be wrong. Since I just purchased the vehicle, and the warranty ran out, I didn't want to have to take it to the shop.......thanks again.

 

[RonkonkRunner]

Funny, I was wondering the same thing. I just bought an '01 Sport a few months ago. I've been trying to pinpoint the location of the sound for a while. It's definitely reassuring that there is nothing wrong.

 

[marino]

mine started making that noise more than usually after i changed out my front brake pads... then i realized that the fluid level was above the max in the brake fluid resevoir.

took about 10 fl oz out to get it more in the mid range, and the noise pretty much went away - or went back to normal....

so.... if you've changed your brakes lately might not be a bad thing to check.