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High Idle ??????????

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by dmanblazer, Jan 19, 2005.

  1. dmanblazer

    dmanblazer 1/2 ton status

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    I have a question for you brake guru's, everytime after I start my Blazer and put my foot on the brake pedal before I put it in gear, the engine idle raises a little, is this normal or what? Now I have owned GM vehicles all my life and this has never happened on any of them. The only thing that is different about my engine is, it's a 0.60 overbore 350 with a summit camshaft that has an advertised duration 272/282, Lift .442/.465, with a lobe seperation of 112 degrees. The brake booster is used from a junkyard, it had some type of canister about the size of a fuel filter between the carb and booster that I took off because when I blew thru it there was no restriction from either end, so I thought whatever purpose it had served it wasn't serving it anymore so I took it off. What is it for? Ever since I've owned this Blazer it's never had very good brakes no matter what I do, new master cylinder, calipers, lines, I have even rebuilt the rear brakes. WTF?:mad:
     
  2. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    that canister is a check valve, keeps vacuum in the booster after the engine is off.

    it may be a vacuum leak when stepping on the brake causing the idle to raise a bit. you may need a new booster. instead of running a vacuum booster, id run a hydo booster off a 1 ton or a diesel truck. then you don't have to worry about vacuum :cool1:
     
  3. sweetk30

    sweetk30 professional hooker Premium Member

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    I HAVE ONE EVEN BETTER , i removed the cruise in my 83 i had and when i steped on brake it did that. there is a vacume switch on the pedel by the brake switch.
     
  4. dmanblazer

    dmanblazer 1/2 ton status

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    Well I wish I had the money for Hydro-brakes, but since I just moved here from Indiana it's pretty tight. I have Hydro-brakes on my 1 ton dually and I like them better. My cruise has been removed maybe I'll check for that switch first because it's cheeper. But the main problem I have with the whole brake problem is, my brakes are getting worse!!!!!
     
  5. dmanblazer

    dmanblazer 1/2 ton status

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    anyone else have any suggestions? ttt:grin:
     
  6. 79Beast

    79Beast 1/2 ton status

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    Here's something for you: How is your pedal? If it's rock solid, I'd investigate the brake booster. With the engine off, you should be able to remove the check valve and hear a 'swoosh' of air rushing into the booser. If you don't, either your check valve is bad, the booster is leaky, or your engine just doesn't produce enough vacuum. One thing to try would be adding an additional vacuum reservior.

    If the pedal is soft/spongy, or has excessive travel, you need to look at your brakes. They could have air in the line, you might not have to rod in between the pedal and booster adjusted right, you might have the wrong rod between the master cylinder and booster, or you might just need to adjust your rear brakes.
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    gm booster test is to start vehicle, don't use brakes, turn vehicle off, wait 45 minutes, then test brake apply with engine not started...should still have two full power assists. If not, the booster is bad.
     
  8. dmanblazer

    dmanblazer 1/2 ton status

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    I just bought another booster I'll try it. Thanks guys
     

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