Pedal travel is low and spongy so I thought bleeding is needed. Doing it in the order of LR RR RF LF

Master cylinder is full, but when I pump the brakes and have someone turn the bleeder screw open, no fluid comes out at any wheel. Master cylinder just bubbles in the rear compartment.

No signs of a leak anywhere.

Does this mean too much air in the system or is this a bad MC?

I just went through this.....
You may have a bad master cylinder that is sucking air.
Definitely check that your bleeders are not plugged....I spent 2 hours trying to bleed my system and finally figured out that the previous owner had installed the one man bleeders and they had seized...couldn't get fluid no matter what I tried.
Replaced bleeders and had the system done in 30 minutes.

It's possible air has been introduced to the master cylinder. Knock the brake lines loose at the master, push, tighten, then release. That's the messy method of bench bleeding. Once fluid comes out up there, then it should start traveling down to the brakes.

I think you are both right and will check it out.

I just replaced the cap and gasket on the MC because it was slightly warped. It probably did suck too much air in. And I'm not sure how to check the bleeder screws themselves so four new ones won't hurt.

What do mean by "knock the lines" to bleed it? I'm assuming bleeding it on the car? I have one of the MC bleeding thingies (handle and tubes) but I need to see if I have the right threads.

I just wish I wasn't so old and the car wasn't so low to the ground.

I replaced my master cylinder because it was doing the exact same thing yours is...sucking air.
Bought a new one and bench bled it and installed it....no problem.
When i was trying to bleed my lines at the calipers I did the usual pump and hold routine with no luck.
Then I moved on to a vacuum bleeder...still no fluid from the caliper.
I started at the front of the car and worked my way back....cracking lines wherever I could to trace the flow of fluid....had fluid back to the calipers.
The second I took a bleeder screw completely out I had fluid running everywhere.
Reinstalled the bleeder and same issue....no fluid.

Bleeder screws are cheap....you should be able to replace all 4 for less than $10.....

[This message has been edited by MadProfessor8138 (edited 04-14-2017).]

I went out and tested a few things, specifically trying to bleed the mc on the car. As suggested I removed the side lines and fluid flowed freely. I then put the plastic screws in from the bleeder kit and ran the two hoses back into the master cylinder. Then we pumped the brakes about 100 times and the air bubbles never stopped. I kept hearing the sound of air coming from somewhere so I can only guess it is where the mc runs into the booster, however, there was no loss of fluid doing this. Maybe a seal on the mc?

I also removed the bleeder screw from the left rear and pumped it with no fluid coming through.

Now I'm thinking mc needs replacing, but what exactly broke inside it if that's the case?

The master cylinder is sucking air....sounds like a seal on the piston/plunger has given up.
Replace the master cylinder.....and do the bleeder screws while you're at it and watch your troubles disappear .
I thought I had a proportioning valve issue because i couldnt get fluid from the rear calipers but the new bleeders fixed the problem.
Been there,done that.....AND KICKED IT'S *SS......


I noticed that you said you removed the bleeder from the caliper......realize that with the master cylinder not supplying any pressure that you are dependant on gravity to move the fluid....it could possibly take hours for the fluid to finally creep through the caliper.....and if the caliper isn't the low spot in the system it's possible for the fluid to NOT make it through the caliper at all.
You didn't state how the car was situated.....level,raised in front,raised in back......etc.
Do you still have the emergency brake cable still attached?.....try setting and releasing the emergency brake a time or two.
If the cable isn't attached then manually move the lever on the caliper a few times.
Have you tried bleeding the front calipers?.....do you get fluid from them?

[This message has been edited by MadProfessor8138 (edited 04-14-2017).]

I didn't get any fluid on LR RR or RF when I opened them up and had my wife pump the pedal.

Definitely sounds like you have multiple issues. I would replace the rubber hoses and the master cylinder. If the rubber hoses are original, they're about due to collapse internally. They're pretty cheap, so it's a worthy maintenance part anyway.

What viperine said .......

[This message has been edited by MadProfessor8138 (edited 04-14-2017).]

quote Originally posted by MadProfessor8138: Bleeder screws are cheap....you should be able to replace all 4 for less than $10.....

Kind of ruins your day though when they snap off in the caliper.

Yes it does.....that's why I try to soak mine for a few days prior to having to turn them.
I've actually had to replace a caliper before because of a snapped bleeder.
But the OP said he couldn't get fluid to flow from the bleeders so I assumed he already has them broke loose.

I think I got everything working again. Once I disconnected the master cylinder lines, fluid started flowing again. I changed the mc, changed the bleeder screws, and bled the system several times. It seems to be stopping pretty well though I do wish the pedal was more sensitive than the travel it has.

Thanks to everyone for their advice and guidance.

quote Originally posted by MadProfessor8138: ...that's why I try to soak mine for a few days prior to having to turn them.

I soaked the bleeders on my '86 GT for a couple weeks, sprayed them several times with PB Blaster. I was ever so gentle... and both rear bleeders snapped right off.

quote Originally posted by MadProfessor8138: But the OP said he couldn't get fluid to flow from the bleeders so I assumed he already has them broke loose.

It's not just the OP who reads our responses. I was simply warning the newbs.

[This message has been edited by Patrick (edited 04-23-2017).]

quote Originally posted by viperine: Definitely sounds like you have multiple issues. I would replace the rubber hoses and the master cylinder. If the rubber hoses are original, they're about due to collapse internally. They're pretty cheap, so it's a worthy maintenance part anyway.

Me too.