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Discussion Starter #1
2007 Rav4 Sport V6

About six months ago I replaced the brake vacuum booster with a new unit from Rock Auto. I had P0171 and P0174 codes, a hard brake pedal, intermittent rough idle, and the hissing sound from under the dash.

The hard pedal and rough idle went away but I am still getting P0171 and P0174 intermittently. Yesterday I also got a P1578. I still hear the hissing sound under the dash.

The question:

I still hear the hissing sound under the dash. Is that normal for a Rav4? It is not normal in any other car I have owned. Is the new brake booster defective?
 

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2007 Rav4 Sport V6
I still hear the hissing sound under the dash. Is that normal for a Rav4? It is not normal in any other car I have owned. Is the new brake booster defective?
That doesn't seem or sound at all normal to me. You'll need to find the source and fix it, but since I doubt any other members have the issue you'll have to sleuth it out yourself. When you do I suspect the other symptoms and codes will be cured.
 

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Discussion Starter #3
So when you are sitting in your Rav4, engine running, you do not hear a hissing sound from under the dash?

Is there a vacuum dump valve for the cruise control?
 

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No such sound on our RAV4.
With throttle-by-wire cruise control is electronic not vacuum.
 

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Discussion Starter #5
I took another look/listen. At an idle i can hear a hiss under the dash. The engine is around 900 rpm. When I depress the brake progressively harder the hiss diminishes until I reach the end of the pedal travel and the hiss stops. The rpm's drop to around 600-700.

This is an A1 Cardone brake booster that I installed in July. I'm going to have to return it to Rock Auto. Has anyone else had problems with A1 Cardone boosters?
 

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I have an 07 v6 limited. My booster is doing the same thing, hissing by the pedal. I have taken it to a shop to confirm its the booster and they said it was. Did you replace the booster yourself? And if so how did you get it out? I have taken out the master cylinder and disconnect the booster from the firewall and brake pedal but still can't get it out.
 

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MrsT, maybe someone else will answer but I doubt a member we haven't heard from in 2 1/2+ years will. However we do appreciate your using the search option before posting.
 
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