Mechanics

BRAKES DON'T WANT TO STOP AT FIRST BUT THEN THEY GET LIKE THEY ARE SUPPOSE TO BE AFTER STOPPING A FEW TIMES.

2003 Volvo S40

Just changed the pads all the way around, put in new master cylinder. Not sure what the problem is with starting out bad at first then getting better.
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Cp72
November 22, 2011.




Is the brake pedal hard to push or anything like that?

No it's like they don't grab at first
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Tiny
Cp72
Nov 22, 2011.
Did you try bleeding the brakes? Also, was the plunger on the MC adjustable?

Bleed the brakes several times and no the plunger on the master cylinder was not adjustable.

Tiny
Cp72
Nov 22, 2011.
That is odd. Is this the same problem you had before replacing the brakes and MC? Did you check to make sure none of the rubber brake hoses are collapsed and the calipers are responding properly?

Sorry for so many questions.

Yes the same problem just thought replacing all these would fix it. Hoses are fine and calipers are also new.

Tiny
Cp72
Nov 22, 2011.
The only thing I can think of is a proportioning valve may be sticking.

Ok thank you. Will have that looked at and hopefully that will be all. Thanks again

Tiny
Cp72
Nov 22, 2011.
Let me know what you find.

If you are talking about at the very beginning when you start it up cold and feels like the brakes are not grabbing it is because the brake pedal actually is hard. There is an electric vacuum pump that assist during that start up to get enough vacuum to the booster. Youy could either have a faulty vacuum solenoid switch or the vacuum pump itself has failed. With the key on engine off, pump the brake pedal several times. You should hear the vacuum pump come on. If you do not, disconnect the connector and with a volt meter check to see if there is voltage at the connector while pumping the pedal. You should see voltage while pedal is pressed down and no voltage when the pedal is not pressed. Like an "ON" and "OFF" switch. If you have constant voltage the solenoid is shorted out and burnt up the vacuum pump motor. If there is voltage when pumping only then the motor is faulty. If no voltage then disconnect the vacuum solenoid connector and using a paper clip or jumper wire, jump the 2 pins on the connector to complete the circuit. There should be battery voltage at the vacuum pump connector with that test. Plug the connector back to the motor to see if it comes on. It should with the solenoid connector jumped. If it does not then both the solenoid switch and vacuum pump motor have failed. For the most part it is the solenoid that failes. The solenoid is part of the vacuum hose assembly from the intake. Hope this helps and let us know if you need more info and please let us know if this has helped you out as well since others come to this forum that may have a similiar problem, this would help them out as to what the fix was? Good luck to you.

JIS001
Nov 22, 2011.

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