Odd sound (humming?) that may be related to braking.

[Ruffian]

Ok so I've searched and searched. I know there has to be someone else who has brought this up, if so I can't find the thread. So this is a sound that I've heard since I bought Ruffian. However, now after I've installed the OME lift, I'm hearing A LOT more. This is very similar like when the air compressors recharge. Of course in a whisper compaired to the rumble an air compressor makes. I have this feeling it's related to the braking system since it occurs mostly when I'm applying the brakes, or just after. All I can surmise is that it's something recharging in a airy humming tone....somewhere. Any ideas?
And no, I don't have an on board AC, that's on the list of to do things. And no, I have not extended my brake lines after the lift as it didn't look like I needed to.
Thank you in advance for your help.

 

[Se7enRed7]

I recently purchased my 03 V8 4wd and have noticed the exact same thing. It's probably been talked about before, and i'll do a little more searching.

 

[Ruffian]

One response I got. Looking into it just to educate myself.

"It's the brake controller filling the resivoir thingy, totally normal."

Def. of a brake controller:
A vehicle braking system evacuation and fluid fill machine which utilizes a lightweight, compact filler head which is easily mounted on top of the vehicle master cylinder and a venturi type vacuum pump which effectively vacuums the air out of the vehicle brake system in order to allow brake fluid to enter and completely fill the brake system.

 

[drmorbius]

One response I got. Looking into it just to educate myself.

"It's the brake controller filling the resivoir thingy, totally normal."

Def. of a brake controller:
A vehicle braking system evacuation and fluid fill machine which utilizes a lightweight, compact filler head which is easily mounted on top of the vehicle master cylinder and a venturi type vacuum pump which effectively vacuums the air out of the vehicle brake system in order to allow brake fluid to enter and completely fill the brake system.

It's a pump and it allows you to have power brakes even if the engine isn't running. The key has to be on though.See RickyCRX's post here

 

[Ruffian]

Thank you sir!

"4th gen 4Runners don't have vacuum lines running to the brake booster. There is a vacuum pump that runs as soon as you turn the key on, and you'll end up having power assisted brakes without the engine running as long as the ignition switch is on."

So then that answers my question for the most part. I'm going to look over this system and make sure everything is tight. I hear this pump an awful lot. And with the lift, people have asked if I used brake line extensions, which I haven't. I want to make sure I haven't stressed those lines.

Thanks again.

 

[drmorbius]

Thank you sir!

"4th gen 4Runners don't have vacuum lines running to the brake booster. There is a vacuum pump that runs as soon as you turn the key on, and you'll end up having power assisted brakes without the engine running as long as the ignition switch is on."

So then that answers my question for the most part. I'm going to look over this system and make sure everything is tight. I hear this pump an awful lot. And with the lift, people have asked if I used brake line extensions, which I haven't. I want to make sure I haven't stressed those lines.

Thanks again.

Glad I could help, I knew I had seen it somewhere and I finally remembered RickyCRX! Hope everything is OK. She is a beautiful female!

 

[4RBob]

My brake pump seems to be running much longer than it used to. I can't find any leaks and the brake fluid level is correct. Front brakes were bled not too long ago when I did the calipers, but this started before then and is about the same now.

What else should I look for? Is the pump dieing? Should I bleed out all the old fluid and start fresh?

 

[wombie]

I had this problem, and it had a rather expensive fix.

The master cylinder assembly was not functioning correctly. It would vibrate so much that the vibration would go up the brake pedal - essentially I could feel it every time I braked, which was darn annoying (aside from being potentially dangerous).

If you start up your truck and put it in park then open the hood and have a buddy press down on the brake pedal you should be able to hear the master cylinder assembly (brake booster etc) whirring away. It's normal for it to do this, though because it's up by the drivers side it's more audible than other stuff than makes noise.

Replacing the brake booster parts did not fix the vibration problem for my truck - only replacing the entire master cylinder. Fortunately it was under warranty.