niseguy

I have the 2004 Sport Edition with the V8 and am curious if anyone else with a similar model hears an electric motor or pump noise when they turn the key to "on" when the truck is cold. It will normally run for about 15 sec. initially then turn on again for a couple 5 second intervals. Seems to me like it is a pump that is pressurizing a system but I can't tell. It is right behind the dash somewhere maybe on the other side of the firewall. I can't seem to remember this happening soon after I bought it. It seems to happen more when the truck is cold, winter, versus warmer outdoor temperatures.

Also, in anyone's 4Runner with the V8 is there a time lag between shifting out of reverse and going into drive? Mine seems to have a pretty good lag when shifting R to D like when coming out of a parking spot. I'll see if I can time it but I was interested to see if anyone else experienced this situation.

Thanks....

LifeOnABoard

I have this same nosie. Does anyone know what it is? I'm worried that it is a vacuum pump that is compensating for a leak.

GSGALLANT

Do you have a traditional vacuum brake booster, or a hydraulic brake booster on the 2004? My 2002 4Runner, and I know the 2001 4Runner has a hydraulic brake booster, and I suspect the 4th gens might also have them. If that's the case, then that noise is normal. It is the brake booster pump motor that you hear.

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 probably the relay snapping off).

If you don't have a hydraulic brake booster, then ignore this post.

LifeOnABoard

I've been driving my 01 for a week now and didn't think about the noise too much then my gf gets in the truck with me and says: "It sounds like the brakes are re-calibrating themselves."

Now she is the epitomy of girly girl who knows nothing about anything electrical or mechanical. Needless to say, I was totally shocked to hear that come from her mouth. And that's when I started to think maybe climate controls/cruise control or brakes.

Good to hear that it is normal, thanks. But I'm kind of surprised that Toyota would put such a noticable mechanism in their newer vehicles. Maybe a system flush would help it out.

GSGALLANT

System flush will do nothing for the noise. It's really not that noticeable... a bit of a whiiirrrrrrrr-click, that's all. My ventilation fan is louder than my pressurizing pump. If yours is loud, there may actually be a problem, but if your braking power assist is working well, I wouldn't worry about it unless its really loud and annoying. If my radio is on normal level, I can almost not hear the pressurizing pump at all.

LifeOnABoard

I only hear it when I drive with the radio off so I'll just try to ignore it. Oh, I'm also guessing that it gets quieter as the weather warms up. It's typically 10-20 degrees in the morning here.

GSGALLANT

I just now noticed that you revived a 5 year old thread when you made your first post... oh well, it's good that you searched for an existing related thread before just starting a new one on your own.

Mad Jack

I know this post is pretty old, but I'm starting to have issue with mine. My 04 with the hydraulic assist is starting give less and less boost. In other words, it is taking more pedal pressure to stop the truck. It seems to stop fine, but it reminds me of driving old school...with no power brakes. The motor on the bottom of the unit is really much louder than it used to be. All I can find is pricing for the entire unit, has anyone rebuilt them or had any experience with this same issue?

LifeOnABoard

Mine didn't get any quieter with the warmer temperature. My brakes work great first stop after starting up but after that point it takes more pressure than it should to stop. I don't mind it too much, I tend to stop slow anyways to save wear on the rotors.

Also, I've read that my generation has a calibrating system for the rear brake shoes. That could be why it is on and off so much.