Whys it do this

[Difflock]

When I park my runner, engine off, key out. I hear buzzing on and off, coming from my brake booster area in my engine bay. Ive heard other 4runners do the same thing too. What is it and why does it do that, its been making me curious for years


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[Tyler James Inc]

ABS pump [emoji1360]

 

[185Runner]

Thought it was the evap system. Aka the "moo box"

 

[pluton]

Brake booster leaking vacuum?

 

[Difflock]

Brake booster leaking vacuum?

Naw nothing like that. Sounds like its supposed to do so


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[Difflock]

Thought it was the evap system. Aka the "moo box"

Bang on, thanks dog


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[JohnMc]

You can cure this extended 'mooing' by adding a small added volume on one of the hoses. The later model (not sure what year) evap control boxes have an extra chamber built in.

You could swap with a junkyard later version, but that's a PITA. It's easier to get a small container and a couple of hose fittings, and add one inline:

Looks goofy, but it works. Why? Who knows!

 

[Tyler James Inc]

Hm, don't think I've heard the "mooing" sound before.

 

[SaulG]

Some models of 3.4's had an added "muffler" on the cannister..used to be a TSB