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98 GMC 3500 w/454 Got Questions

Discussion in 'Chevy Trucks' started by mojob, Sep 7, 2006.

  1. mojob

    mojob Member
    Messages: 83

    My truck has a hard time starting after it's warmed up. You have to crank it about three times before it starts, and it seems to start when you let go of the key. It also has a hydraulic brake assist instead of the regular vacuum booster. There's a slight leak coming from what looks like a small cylindrical part mounted on the hydraulic unit. Does anyone know if this is servicable or do I have to go to the dealer and bend over again? I have already replaced the fuel pump and fuel pressure regulator because of previous problems.
     
  2. FSUPERDUTY

    FSUPERDUTY Senior Member
    Messages: 311

    Turn your key to on wait a few seconds for the fuel pump to cycle then hit the key.If it starts you probably need a fuel presure regulator! Fuel pressure is bleeding down,Vortech's need at least 55psi to start.while your at it do the intake gaskets they are probably leaking too! let us know.
     
  3. FSUPERDUTY

    FSUPERDUTY Senior Member
    Messages: 311

    I guess I should have read your post more thurowly,saw that you replaced the pump and regulator already.have sombody put a presure gauge on it to make sure one of those parts didn't fail.
     
  4. sweetk30

    sweetk30 PlowSite.com Addict
    Messages: 1,588

    96 and newer vortecs have a real bad problem with dist caps and rotors. if you need to replace it only get napa prem unit or ac delco. those 2 are the best. ask me how i know.:cry:
     
  5. Travel'n Trees

    Travel'n Trees Member
    Messages: 85

    Does it smoke when you start it? Leaking injector or injectors bleeding off while not running.
     
  6. joe_padavano

    joe_padavano Member
    Messages: 68

    Hydroboost leak

    The cylindrical part is the accumulator that retains hydraulic pressure after the engine shuts off. This lets you have power boost for the brakes for a short time in the event that the engine stalls. Leakage means you'll be losing hydraulic pressure, so you probably want to replace the hydroboost. I bought a rebuilt one from the local autoparts store and put it in myself. The real problem is the mess that the power steering fluid causes when it leaks out after you disconnect the hoses. Once the new hydroboost is installed, you'll need to refill the power steering pump and bleed the system. You do that by raising the front wheels off the ground (to eliminate load on the pump while the fluid level is low) and slowly turing them back and forth with the engine running. The system will probably make a whining noise initially. Also, expect to see foam in the PS fluid. Continue to top off the fluid and turn the wheels until the fluid level doesn't change. In my case, it took a few miles of driving to get all the air out of the system and for the whining to stop.

    I don't know about annual safety inspections where you live, but here in Northern VA, I was failed for a hydroboost fluid leak like the one you describe. Since this system ties the power brakes and power steering together, the inspectors are told to look at it closely.
     
  7. mojob

    mojob Member
    Messages: 83

    Is there anything weird or important to know about swapping out the hydroboost. The accumulator has a warning "high pressure" stamped on it. I just don't want any surprises. Also, the truck doesn't smoke and runs pretty good although I think it could idle a little smoother. I did replace the upper intake gaskets when I replaced the pressure reg. and I drove around with a pressure gauge taped to my windshield just to monitor the fuel pressure. The pressure is good(about 60 psi at start up). I want to thank everybody that posted. Any other ideas? Why does it fire as soon as you let go of the key?
     
  8. joe_padavano

    joe_padavano Member
    Messages: 68

    Pump the brake pedal several times with the engine off to relieve the pressure in the hydroboost before disconnecting the hoses. You'll feel the higher resistance in the brake pedal. At that point, it's safe to take it apart.