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Blew a brake line last night...on the 6.5

Crankme69

Crankme69

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The front passenger side brake line blew last night on my way home. Changed the line out for new, now I can't get the friggin pedal to stop going to the floor and the master cylinder has a drip between it & the booster weird noises when pumping the pedal :eek:

Bleed the brakes for about a hour, me & my son, went through almost a full quart of fluid, the pedal seems fine until I start the truck then it goes down way further then it ever did before & when pumping the brakes listening to the master sounds like it pushing air or gurgling weird. Not happy & worried that changing out the master next if that don't fix it then what???

Friggin old chit...:mad2::mad2:
 
Sounds to me like air got back to the master cylinder and damaged it. Sorry to hear that blew out on you. Told you guys doing burnouts with the brake pedal to the floor was a bad idea without braided stainless lines :D:D:D

In all honesty it sounds to me like air killed the master cylinder. Your best bet is to replace it. And if money allows... Offroad Design makes some killer braided, stainless brakes lines :D I have yet to make these things even budge!
 
Crankme69 said:
How is that done?
Click to expand...

wow I just had a thought. you may need to have your system bled by a computer. you can thank your ABS unit for this. Due to ABS, you cannot bleed brakes like you would one without(cracking the bleeder and pumping the brakes), someone needs to use a computer to cycle the valves and cylinders in the ABS unit to fully "bleed" the system.

Try that before you get a new MC
 
The only MC I've bled are pre ABS. A hose is is installed from the line outlets back to the filler holes and the piston is cycled until no air bubbles appear. If it is leaking between the MC and the booster the piston seal may have blown.

Did the reservoir run out of oil? If it did then the MC and all 4 brakes will have to be bled.

Start with LF, RF, LR then RR
 
I thought you start at the furthest away from the master. rr,lr.rf, lf. I used a mighty vac and sucked the brake fluid through. Didn't have a problem. I didn't blow a line though. I was just changing the fluid as pm.
 
When my pickup blew the rear brake line it bled just like a non ABS system.

It does sound like your master cylinder's dead. Probably the rear seal on the MC if your getting a drip between the MC and the booster. Ther's a little weep hole there to drain fluids.

My original MC on my blazer had a bad rear seal, and i totally ran out of brake fluid one night for the rear brakes due to that leak. The second MC i installed was an autozone rebuilt one that worked fine at first but then the rear's quit working. Bad seal from the rebuild.

If your MC sucked air you can "bench" bleed it right on the truck. Here's how i did it.

  1. Leave the engine off for this entire procedure.
  2. get yourself an MC bleeding kit (which comes with fittings and flexible hose) so the output's of said lines go back into the reservoir and under the fluid level in the reservoir.
  3. Brake pedal all the way down slowly then release.
  4. Repeat step 3 until you see no more air bubbles coming from the lines in the reservoir.
  5. Now remove either the lines your created to bleed the system, or the MC bleeding kit and hook up the lines going to the brakes again.

You will still have to bleed the brakes to get all the air out of the system however. I've always started the brake bleeding with the wheel/line furthest away from the MC.
 
If you blew a line the diverter valve will flip. It wont flip back again until you build enough line pressure,it can be a real pain, start at the master cyl,and then maybe at the abs. All the plastic cap master cyl make a goosh sound,also on hydro boost you must wait a little between pumps as the pedal comes up slow.
 
A MC can be bleed without a kit or cycling the ABS. (Having a bleader kit does make it a lot easier)

You will need to make sure the MC does not have an air bubble trapped. Pump up the system and loosen each of the lines at the MC, or at the ABS (is best). This primes the MC. Then bleed the rest of the system. Cycling the ABS will get the last of the air from the system, a gravel or snowy road works.



I blew out my rear lines last year. I replaced every line but the second half of the right front (because of no line rust). I never even cycled the ABS, the brake bleed fine, but the MC must be primed.

Note the system cycles brake fluid between the MC and ABS. If the back port is not bleed, it will loose prime. You've probably been mainly bleeding just the front chamber.

Check and see if you get air from the MC lines.
 
Hey thanks to ALL for the suggestions and replies, much appreciated.

I'm at work right now, my Son did the bleeding and I did the pedal pumping, he changed out the new brake line, thank God for him, there is NO way I can crawl under these rigs anymore, I have way too many aches & pains on a regular basis without that influence.

Hoping my boy will have it all figured out when I get home from work tonight, we'll see...

Thanks again & if anyone has anything else to add, please chime in!

We’ll give ya all a reply after we get it figured out…

69
 
you don't need to activate the abs to bleed these trucks, gm says you only need to bleed the ABS when you change ABS solenoids.

If you have brake fluid from between the master and the booster, then the master is junk. good news is they are cheap as hell for these trucks.
 
You guys are correct, RR, LR, RF, LF. I must have had a dyslexic moment.
 
We got it, 1st we bled both the master cylinder inlets into the ABS, 2nd we bled all three of the ABS outlets & 3rd we bled the RR, LR, RF & LF 3 times each.

Thanks for the replies, it got late last night & we were both cold & tired.

Much better luck today with it...Thanks again All 69
 
540s10 said:
you don't need to activate the abs to bleed these trucks, gm says you only need to bleed the ABS when you change ABS solenoids.

If you have brake fluid from between the master and the booster, then the master is junk. good news is they are cheap as hell for these trucks.
Click to expand...

That's one reason I love these rigs. Repair parts are pretty reasonable.

Good luck - I think the guys covered all the options.

-Rob :)
 
Glad you got it fixed. I AM, however, going to ask you guys to post these non 6.5 specific threads in the right sections. This one goes with brakes. Us guys with the DMaxes, Cummins and PStrokes haven't always had them. For example, I've had the following GM trucks: '69, '83, '89, '92, '94, '97, '99, '00, '02, '03, '05, '06, & '07. I worked on every one exclusively... a couple for over 300k miles. There's a whole bunch of tech knowledge on here from the rest of us and we'd like you all to join us as often as you can. We like to help too.

I'm gonna post this same thing in the OTHER brake thread that's stuck in the 6.5 forum. I don't wish to pi$$ in anybody's Post Toasties, but I'd really like to see you guys make friends with the rest of our brotherhood here.
Thanks
 
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