Outer Limits 4x4 Board

Hey guys,

I just bought a 1998 4runner limited with a 3.4L gas engine
and I noticed that it emits a short kitten like meow when
you start the engine and when you are accelerating between
1500 to 2200 rpm. It does not seem to affect the engine
performance except that it sounds irritating. The previous
owner said, it has been like that for more than 1 year now
but it does not affect driving and engine performance.
I also experienced it myself first hand.
Anybody experienced something similar? Is there
a way I can disable this? Many thanks in advance.

Have you checked under the bonnet for a cat??

Because your car's a pussy?





But no, sorry, I know nothing about the 3.4L's.............

Have you checked the drive belts are tight?

Im sure its not a belt. I know the squeeking sound of a belt.
I will get a video with sound . It will be easier for you to
analyze it this way.

check the harmonic balancer.

Matt

Im really getting desperate and almost ready to regret buying a 4runner.
After 2 weeks of trouble shooting and diagnosing the problem, Im not
nearer solving it than the day we first started. We have opened the
dashboard and check components and has not found anything unusual.
Anybody has experienced this problem?

Anyway the sound occurs at about 1,800rpm and the vehicle must be in drive
and moving . Lower or higher rpm does not produce the sound. If you step
on the brakes lightly, or increase, decrease rpm the sound disappear.


The sound is coming from the left side of the dashboard near the fusebox
in a left hand drive 4runner but we cant locate it because there is no sound
when you are at Park even at 1,800 rpm.

Here is a youtube video of the sound.

http://www.youtube.com/watch?v=aQ0LDCcEA3A" onclick="window.open(this.href);return false;

Need help. Thank you very much.

something to do with your brake booster mate.
possible the seal where the shaft goes in from the pedal.

No idea what's wrong with it but it would seem to be brake booster related.

Thanks for the lead. I will work on this tomorrow.

turn the radio up

I susp brake vacuum booster, You probably don't hear it in park as you don't have your foot on the brakes.
You can try disconnecting and plugging the vaccuum line from the Alt/vac pump and work your way back until the booster, it could be the anti bleedback valve if fitted

I have also searched the net for brake boosters making a whining sound,
But all of the problems discussed in other forums is the sound being
produced when you press on the brake pedal.

My 4runner behaves differently, it produces a whining sound at 1800rpm
and disappears when you step on the brake pedal even so slightly.
I have already printed the 1997 4runner service manual. Any recommendations
where I should start? Again thank you very much for the wonderful
tips.

Sounds a bit like a high pressure air/vacuum leak, you know like when you crimp a balloon and let a little air out?

Maybe those RPM is your max vacuum range under load. When you apply the brakes the vacuum assisted brakes absorb some of the pressure and eliminate the noise from where the air is escaping (or ingesting.)


That's my half-educated guess. I suggest following and finding every vacuum line from the engine, especially the large one to the master cylinder/brake booster. If it is a leak it will likely be a very fine crack, hence producing the wind instrument sound

Hey you guys are a mechanical Geniuses.

I followed your lead and started inspecting the brake booster
assembly. Tested by removing the vacuum hose that is connected
to the brake assembly (shown in the picture) and the noise
disappeared ( of course we had to be very carefull travelling at
1800 rpm with the vacuum line disconnected) .




Its probably a very small leak and it is inside the cabin not outside.
Now that we know what the problem is, its much easier to repair.
I will keep you posted on what eventually is wrong. Many thanks
guys. You are just incredibly wonderful!!!!!

Hey guys,

I replaced my brake booster and problem is solved. I just want to say thank
you very much for pointing me to the right direction. We have been looking
for the problem for the past 2 weeks and was not succesful and if not
for you pointing us to the right direction, we probably would have not found it. Thanks again.