2003 Rav 4 almost stalls when pressing the brake

[bohemian83]

Had this problem now for a few months, its not a constant problem but annoying.
when pressing the brakes and at almost a full stop the car seems like it wants to stall. dropping down to almost the 500rpm line.
and while holding the brake it seems to dip down closer to floor.
does anyone know much about the vuccum line in a 2003 rav 4 crusier automatic or have heard of this problem.

[wa5]

Brake booster failing perhaps?

[jabbatron]

..........

[wiso]

I was thinking along the line of the booster, or perhaps the 1 way valve in the vac line to it. Does anyone know how to test the booster on car, or do i have to pull off and dismantle to check?


When we bought it we drove a few ravs that had this same problem (at least half of the number we test drove), but this one did not at the time. it has begun to develop over summer. So at a guess its a common problem on the rav, but not many people know anything about it

[amichie]

Does it do this at idle when the car is not moving?
Can you pinch off the vacuum line to the booster and see if the problem goes away?

[wiso]

when running no, not normally only once being driven and coming to a stop at in intersection (once the cold start cycle has finished) it happens, more so seems to happen when you brake heavy. And not all the time. It is very intermittent. originally it only started happening on the really hot days we had in Sydney over summer we thought we had it pegged, but then it started on any random days.

I can have it idling when hot in the drive way, press the brake and the issue doesn't happen

[Dazza]

Are you moving the steering wheel at all when this happens? The power steering pump should have a pressure switch on it that increases idle speed when you use the power steering. The pressure switch can fail so the idle speed isnt increased when you use the power steering, which will let your engine almost stall. If you have air con this will also have a setup that increases idle speed when the air con pump runs. The air con fast idle could be faulty.

[wiso]

No its just straight braking, no steering movement. It never does it when the air con is running, the idle up is enough to stop it. some days we put the a/c on when it is happening just to stop it.