2007 Silverado issues...need help

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by Txtruck84, Feb 11, 2014.

  1. Txtruck84

    Txtruck84 New Member

    Well it's been a busy couple of months and I have neglected my truck a little bit I was going to do some repairs this weekend but I need some help on a couple issues.

    2007 Silverado classic crew cab 4.8 I bought it new

    The first issue is the brakes.... I have replaced the drum brake cylinders and inspected the calipers for leaks but for some reason this thing eats break fluid (a big bottle a week) I can't find the leak anywhere. When I push the brake pedal it makes like a bubbling noise. Not sure...any ideas? Master cylinder maybe? How do I check?

    The next is a knocking noise and a rough idle every time I stop to fast. It starts to idle really rough and make a knocking noise when I stop to fast or take a turn to fast what would cause this? It also will occasionally make a lot of white smoke too. I changed the oil and put some stabilizer in it but it still does it. The truck has about 180k and the last time I changed the oil it was super low... However there are no spots on my driveway so I assume it is burning the oil. I figured maybe the oil pump...any suggestions?

    The next thing is the check engine light come on occasionally then goes off after a bit. I haven't plugged in the code reader to see what it is but it happens often.

    The he last thing is the radio....for some reason the radio only uses the tweeter I am not sure if it's the head unit or what but sometimes it will randomly work but the majority of the time the only speaker that it uses is 1tweeter which drives me crazy. Should I just replace the head unit?

    Any and all help would be greatly appreciated
  2. Scott_Anderson

    Scott_Anderson Rockstar 100 Posts

    My one suggestion could relate to multiple issues. Check your brake master cylinder for piston seal leaking fluid into the vacuum booster.
    This could explain fluid loss and rough engine performance and white smoke......

    Not saying it is, but it seems plausible considering the symptoms you are describing.

    To check it, you could try and pull the vacuum hose loose at the motor end and see if you have any brake fluid in the line. Otherwise you would need to pull the master cylinder off and check for fluid leaks from the seal.
    If the MC is the source, I can't begin to suggest how to clean the booster. I know that they can be very dangerous to take apart.
  3. zuki82

    zuki82 Member 1 Year 100 Posts

    I'm pretty sure its the MC! Loosen the two bolts that hold it to the booster, and tip it up, if there is fluid behind there, its the MC. If you take the booster vacuum line off and it has fluid in it, then you might as well change the booster too!
    Just my .02cts worth!
  4. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    I agree with checking the mc. check for fluid running doen the front of the booster where the mc mounts to it. If no fluid there, then look under your dash. Look where the rod from the brake pedal goes thru the fire wall. Many times when a MC leaks it will leak into the booster and the booster leaks into the cab thru the area I described. Burning oil usually makes blue smoke, not white. White is coolant or water burning.
  5. Txtruck84

    Txtruck84 New Member

    Yea that would make a lot of sense the check engine has the code that its running too lean but it would go away after diving a few min or sitting for a while. Il check it tonight. Would it just be easier to replace the booster and mc rather than fixing? They are $30 on ebay used.
  6. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    does it have a vacuum booster or the hydro booster? I would not put used on. It is your brakes, not worth the risk. You might have the same issue when you install the used parts. there were different vacuum boosters sold for that year, rpo codes: JC3, JF3, . each code had a different booster. So, you can not guarantee that the one on ebay is correct. you may be better off searching for parts for an 2006 model as yours is a classic and the same as the 06. Most parts stores do not have data base information of the "classic" models of any given year so searching the previous year usually nets the correct results.
    Last edited: Feb 12, 2014
  7. Txtruck84

    Txtruck84 New Member

    How do I find the codes for the rpo?

    99'HEARTBEAT MODERATOR Staff Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    Inside your Glove Box is a White Tag/Sticker....which is the Service Parts I.D. Tag(Pictured Below)and on it you will see your Vehicles Vin # Number and a Series of Letter's and Number's which are RPO Codes.....which stands for Regular Production Options...In Short what your Vehicle came with from the Factory....and you'll be looking for those RPO Codes that Pikey Mentioned Above,

    Here's the Service Parts Identification Label

    If go to the Link Below, and Enter your Trucks Vin # Number, it will Show you All the Features your Silverado Came with from the Factory, along with All of the RPO Codes, for those Features.

    Last edited: Feb 12, 2014
  9. j cat

    j cat Epic Member 5+ Years 1000 Posts

    before you buy parts follow the instructions given to determine what you need.

    if the master is leaking brake fluid into the brake booster then you will need a new master and a brake booster. these are items you DO NOT FIX .....

    Also you will need to replace the vacuum line from the booster to the intake vacuum port... If this is indeed the failure you have you may also have other problems cause brake fluid is destructive to rubber type parts..O2 sensors could also be damaged....
  10. GM Customer Service

    GM Customer Service Epic Member 5+ Years 500 Posts


    I am sorry to hear that you are experiencing an issue with your vehicle. As a customer service representative, I'm not able to provide much in the way of do-it-yourself information, so I'm glad to see forum members are beginning to step in with feedback. If you have any lingering concerns please private message me.

    Jennifer T.
    GM Customer Care

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