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fastfred

fastfred 11/7/2011

2003 GMC Yukon Denali Base 4. Cyl 2.5L

Brakes

When applying the brakes on hard stopping the peddle stops goes to the floor and stays.

I have to step on it again to get it to return to the normal hight.Only does it during hard stop.No abs light on.

2 Answers


HouseCallAuto

HouseCallAuto 11/7/2011

I believe that you are experiencing false abs activation which is usually caused bt=y a bad left or right front wheel speed sensor. This is diagnosed with the use of a scan tool and a road test while viewing live sensor data of the speed sensors. One of them will read incorrect or not at all sometimes. *Usually*

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HouseCallAuto

fastfred 11/8/2011

I was told by a master tech that it was the master cyclinder.That the vavle was sticking causing this problem.He ask me about the ABS but the light never came on or flashed.On another car years ago I had colasping brake lines causing the peddle to stick.

HouseCallAuto

HouseCallAuto 11/8/2011

After re-reading your details I agree about the master cylinder possibly being the cause, but I have never seen a bad master cylinder only fail under hard stopping, never. A bad master is a bad master and if you are sitting still and you play with the pedal some the pedal will usually sink down like you describe. But, if no other place to go, change the master and see.

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