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Brake light

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by 69K5, Feb 15, 2002.

  1. 69K5

    69K5 1/2 ton status

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    Well let me first say that I am so happy to be home and moved into my new house. I finally have a place and time to work on my 69. When I was coming home there was an idiot driver. like I'm a perfect driver according to the state of louisiana. yeah right! Any way I had to stand on my brakes really hard to avoid him. When i did my break light on my dash came on. I went ahead and stopped and checked everything. My fluid in the forward part of the container had been sucked dry. Well I topped it off and it works. Or as well as drums can. But I cant get my light to go off. I have seen people talk about a "button" that you push when you bleed them. Where is that at? I cant find it. I also checked for leaks and there arent any. ANy ideas on how to get the light off. I am trying to avoid my favorite old standby of just unplugging the light, because it is the breaks. What is the little wire for that goes to my mastercylinder for? it plugs into the bottom. My breaks did last the 9 hours home and 4 days since.

    Also on my dash it has 4 little gauge spote from left as follows: battery which doesnt move even with a dead battery, engine temp, ????, and then oil pressure. What is the 3rd one for.

    One last question. There is a hard copper? line that comes out of my firewall above my distributor. What is it for? It has some sort off a connector in the middle.

    Ok sorry about all the questions, but I havent been able to get on here for 2 weeks and they have been just building up.
    thanks again

    69K5
    Nathan
     
  2. skyblazer

    skyblazer 1/2 ton status

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    Hey 69, Im fixin a few brake gremlins too. If you sucked the res dry, you will have to bench bleed the master cylinder and the lines again because there will be air in the system. This can be done on the truck if you get a master cyl. bleed kit (two fittings to go on the mast cyl. ports connected to two short hoses routing fluid back to the res.). After the master is bleed, then bleed the lines. The Brake warning light is caused by the shuttle valve in the combination valve being displaced due to lack of pressure in the front lines. It does this to shut off flow to the front or rear in the event of a leak. Either a leak or air is causing it to remain displaced and trigger the light. I think that if you bleed the fronts while using a clamp to hold the metering pin in on the combo valve (on the front under the rubber cover), this will recenter the shuttle valve and allow the brakes to be bled.
    Quest 2: don't know mines empty too
    Quest 3: The copper line is the oil pressure line that routes oil from the engine block to the mechanical guage.

    The brake info is what I have gathered from researching old forums the last couple of days. Search "combination valve information" in the second gen. forum for some extra info on the valve, bleeding and the brake light.

    PS: Why did your res. go dry, do you have a leak?


    <font color=blue>As my truck gets higher my balance gets lower!<font color=blue>[​IMG] <font color=red><a target="_blank" href=http://coloradok5.com/gallery/albuo72>PICS</a></font color=red>
     
  3. californiak5

    californiak5 1/2 ton status

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    69, everything that skyblazer said is correct except for the meetering pin on the combination valve. Since on the 69 and 70 trucks had drum brakes all around they did not have to have the meetering ping in the valve to adjust for the difference in the time that it takes for the brake shoes to contact the drums, compared to the brake pads to contact the rotors. So therefore we don't have to worry about any "pin" during the bleeding process. &lt;img src="http://coloradok5.com/forums/images/icons/smile.gif"&gt;

    If your front res. was dry I would be a little worried about a leak somewhere. Or maybe very, very low brake shoes. But I don't think they can wear enough to drain the master. Maybe a leaky wheel cylinder is the culpret. That sounds more like what it would be and since you should bleed the system anyway the wheel cylinders are pretty easy to change out. Good luck with it.

    Oh yea, after you bench bleed the master like skyblazer said you might want to hook up and bleed the proportioning valve the same way you just did the master cylinder just to ensure all of the air is out of that as well. Then hook up the rest of the system and start the bleeding process at the tire furthest away from the master cyldinder and work your way to the closest.

    See Ya,
    Keith

    "Your just mad cause the voices only talk to me."

    <a target="_blank" href=http://coloradok5.com/gallery/californiak5>CaliforniaK5's Pictures</a>
     
  4. skyblazer

    skyblazer 1/2 ton status

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    Oh yeah, oops I forgot about the drums up front, thanks.

    <font color=blue>As my truck gets higher my balance gets lower!<font color=blue>[​IMG] <font color=red><a target="_blank" href=http://coloradok5.com/gallery/albuo72>PICS</a></font color=red>
     
  5. naranja72

    naranja72 1/2 ton status

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    The fourth hole is for a vacuum gauge, fairly rare option I think. You can buy one from a company such as <a target="_blank" href=http://www.chevyduty.com>www.chevyduty.com</a>, it is on page 28 of their catalogue.

    marc
     
  6. 69K5

    69K5 1/2 ton status

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    Hey guys

    Thanks for all the info. i rechecked the system and everything is bled out. when i hit the breaks with the engine running the piston that goes into the back of the break booster hisses. with the engine off it does it but after a few pumps the breaks get really hard. i think this is causing my break light problem. the rubber boot over the piston is kinda rotted. Do ineed to fix this or just what is my problem with this. I've never had to mess with this part of the breaks before.

    PS The reason my reservoir was dry i dont know. i have only had the truck 3 months and never bothered to check it. the guy that had it before me had left it sitting for 8 or 9 years. I know I know dumb on my part.

    thanks again for all the help.

    69K5
    Nathan
     
  7. Triaged

    Triaged 1/2 ton status

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    Your brake booster should hiss when you apply the brakes. That is the sound of air from the cab going into it to help you brake. If it hisses all the time or does not provide assist for a few strokes of the brake peddle after you kill the engine than you would need to replace it.

    Having your brake light come on can only be a bad e-brake switch, a hydrolic leak, or a bad prop-valve. The hyd. leak could be in the master (can leak internally or be sucked thru the booster), at a wheel cylinder (you have to pull back the dust boot to see if it is lesking), or anywhere else (sorry but anything can leak but the ones listed are the most likely).

    '71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
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  8. 69K5

    69K5 1/2 ton status

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    Triaged,

    First of all thanks for the help. My breaks dont get any resistance for 3 - 5 strokes after the engine is killed. If the engine is running then they never build up resistance. Can i buy a brake booster at the local parts store. For the most part people around here are eat up with the SLS (stupid look syndrome) when it comes to even spark plugs for my blazer. What Am I looking at in changing this? I thought at first that It was just me getting used to drum breaks all the way around, but now i think there is something wrong.

    thanks
    nathan
     
  9. Triaged

    Triaged 1/2 ton status

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    I think you got me wrong?...If the peddle is Hard all the time than that might be the booster...It sounds like your peddle is too Soft. The booster is about the most $$$ of any part in your braking system (around $90). I would replace everything else before I replaced the booster (most of the time it is all shot anyway).

    If your brake light is still on check for a hyd. leak!!

    '71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
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  10. 69K5

    69K5 1/2 ton status

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    Triaged

    I did have you miss understood. My breaks are soft all the time. Now the break light goes off but when I put on the breaks and all the weight shifts it comes back on. Whenever I am completely stopped it goes back off. My break light quit workin too. I keep looking for a leak , but cant find one. I havent had time to take the wheels off and check the cylinders yet. Been moving myself in since I got sent home from recall and moving my parents to a new house, but i will do the wheels this week hopefully.
    thanks for all the help

    nathan
     

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