Master cylinder ran dry

[K5Rob]

Hey guys, adding extended brake hoses on my 87 K5 due to lift kit and finding some cracks. In the process the master cylinder went dry. At the time I thought it wasnt a terrible idea as the fluid looked pretty crappy anyway. Can i bleed the entire system as normal, cracking farthest bleeder first, with helper holding pedal, etc. Or do I need to bench bleed the master cylinder. If so can I do it on the vehicle. Just need some tips. Its been a while since I’ve bled brakes and in reading found that people are having trouble with their square bodies? Also I do not have a power bleeder.

 

[fast 99]

Can be done on the vehicle, bleed normally. For the future there are brake hose clamps to avoid that.

 

[K5Rob]

Can be done on the vehicle, bleed normally. For the future there are brake hose clamps to avoid that.

Okay thanks.

 

[Ricko1966]

Okay thanks.

Don't push the pedal to the floor,you can damage the cups in the master. I'd crack the lines at the master first and wait for it to start dripping, protect whatever is below it from drips.

 

[K5Rob]

Don't push the pedal to the floor,you can damage the cups in the master. I'd crack the lines at the master first and wait for it to start dripping, protect whatever is below it from drips.

Good advice. Thanks. I havent touched the brake pedal yet. Are you referring to the hard lines? Only the rear went dry however I suspect the front will too as I am changing hoses and calipers up front due to seized bleeder screws

 

[Ricko1966]

Good advice. Thanks. I havent touched the brake pedal yet. Are you referring to the hard lines? Only the rear went dry however I suspect the front will too as I am changing hoses and calipers up front due to seized bleeder screws

All the lines at the master are hardlines.Do not touch the brake pedal during this operation. When you are done pour brake fluid in the reservoir and crack all the bleeders. When they start flowing close the bleeders. If they don't all start flowing tighten the bleeders crack the lines at the master when they start flowing tighten them. Then 2 man bleed it. Unless you were planing on vacuum or pressure bleeding in which case ignore everything,I wrote. DO NOT TOUCH THE PEDAL UNTIL YOU have gravity bled,vacuum bled,or pressure bled.

 

[K5Rob]

All the lines at the master are hardlines.Do not touch the brake pedal during this operation. When you are done pour brake fluid in the reservoir and crack all the bleeders. When they start flowing close the bleeders. If they don't all start flowing tighten the bleeders crack the lines at the master when they start flowing tighten them. Then 2 man bleed it. Unless you were planing on vacuum or pressure bleeding in which case ignore everything,I wrote. DO NOT TOUCH THE PEDAL UNTIL YOU have gravity bled,vacuum bled,or pressure bled.

Thanks. Im stuck at work the next few days. Will hopefully get to it Tuesday if the weather’s good.

 

[K5Rob]

All the lines at the master are hardlines.

Ricko hopefully getting to this tomorrow. I havent touched the pedal. I am not getting anything at the bleeders but I am getting fluid at the banjo bolt at the calipers. I have a 9/16 flare wrench that should arrive tomorrow for the master. They are tight.

Should I still crack the master fittings first? And am I looking to get fluid to the bleeders before attempting to build pressure with the brake pedal?

 

[Ricko1966]

If you are getting fluid to the banjo bolts then the master has fluid in it. Go slow don't mash the peddle. I'd pull all 4 bleeders out and make sure they are clean and clear. I'd prefer to see fluid com8ng out of all 4 bleeders.

 

[75gmck25]

As already mentioned, do not get carried away with “mashing” on the brake pedal and pushing it down too far to bleed air. The MC has been on there a long time and the piston seal inside has probably built up a ridge where the pedal stops moving the piston during normal braking. If you push the piston beyond that point it may damage the seal, and you will be off looking for a new master cylinder.

 

[K5Rob]

Ok thanks guys