So picked up my truck today after the stealership had it for a week. They installed a new brake booster and the o-ring as mentioned before by another member. Brake pedal is firm again and all problems seem to be fixed. Thank God for extended warranty dealership charged $600 with parts and labor plus a loaner for a week. Hope this helps anyone looking up the topic .

 

Hello,
I have a 2009 chevy silverado 5.3l and had the "service brakes soon" message for a couple of years. I googled and ended up here a while ago. I finally checked for the o-ring between the master cylinder and brake booster like another fellow said but that wasn't my issue. A new brake booster sensor fixed mine. Got it for $52 off amazon. ABC Auto wanted $120. He tried the sensor but it didn't fix his. Thats why I checked mechanical first. Hope this helps.

 

hey what's the part number for the sensor? I have the same issue on an 07 Tahoe but I don't think the O ring is the issue as there is no evidence of a leak. thanks.

 

The part is: GM Genuine Parts 15823208 Power Brake Booster Vacuum Sensor. It's a Bosch manufacturer. Hope this helps.

 

Thanks! I just ordered it.