I have a situation where I have power brake boost right after I start the car and for 2 or 3 brake applications. Then the boost goes away for a few applications, then returns and is fine all day. This problem seems to have come about this winter.

I haven’t done any vacuum pump testing yet, but I wanted to first ask if a sticking “Non-Return Valve, Brake Booster” can cause these symptoms. Because I have brake vacuum at cold start up I think that means it is working fine at holding a vacuum, but can it “stick” and not allow fresh vacuum until it releases for some reason?

I'm referencing part #140 below.

Thanks.

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1993 W124 300D 2.5L Turbo, OM602.962
2000 Chevrolet Cavalier, 2.4L DOHC
2002 Ford Explorer, 4.0L SOHC
2005 Toyota Prius, 1.5L

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