Bleeding Brake Master Cylinder

[G_Squared]

I'm replacing my master cylinder after the brake pressure went to almost nothing over the weekend. I've just finished installing the new one and am in the process of bleeding the MC. Here's my setup:

Battery disconnected.
Plastic tubes attached to the two ports on the MC on one end, and the other ends fed back into the reservoir.
Reservoir filled enough to keep the tube ends submerged (about 1/2 way).
Pump the brakes until all air is pushed out, only fluid flowing.

Here's the problem:
One of the lines isn't pushing fluid, at all. The one to the front isn't drawing or pushing brake fluid.

Any ideas?

97 4wd 3.4L V6 SR5

Also, this is my first post on this excellent forum. Thanks in advance for any help.

-Garrett

 

[LittleCaesar]

Bleed one of the chambers at a time, not both at the same.

If you have a bench vise, take off the MC and bleed it in the vise. Much easier IMHO and you can make sure the new MC isn't FUBARED, which I have had "new" ones from the auto parts store be bad right out of the box before.

 

[downpour11]

x2^^^

Your very first step should be to bench bleed the new master.

 

[G_Squared]

How do you bleed one chamber and not the other?

I took off the plastic tube, pumped the brakes again, still no fluid through the front chamber, but the back one has been primed.

I took it off to fool with it on the bench. There, I tried priming it with a screwdriver. Same result. Back chamber pushes/pulls fluid, front chamber is dry.

 

[LittleCaesar]

I usually just hold my thumb over one hole in the MC while the other pumps fluid, then switch up.

But it sounds like your new one is bad out of the box. Get another one.

 

[Brian757]

[MENTION=113794]G_Squared[/MENTION]: I may have missed it but how many miles does your truck have?

 

[Andy in Pa]

I usually just hold my thumb over one hole in the MC while the other pumps fluid, then switch up.

But it sounds like your new one is bad out of the box. Get another one.

x2, both chambers should be moving fluid. Sometimes one needs to be blocked to convince the other to pull fluid, but shouldn't happen on a new (or reman'd) OTB MC. I would swap it out for another new one.

 

[G_Squared]

[MENTION=113794]G_Squared[/MENTION]: I may have missed it but how many miles does your truck have?

She's got about 225k miles. Fingers crossed for 225k more!

I usually just hold my thumb over one hole in the MC while the other pumps fluid, then switch up.

But it sounds like your new one is bad out of the box. Get another one.

x2, both chambers should be moving fluid. Sometimes one needs to be blocked to convince the other to pull fluid, but shouldn't happen on a new (or reman'd) OTB MC. I would swap it out for another new one.

I've returned the refurb'ed MC and picked up a new one, this time with a new reservoir, too. As a sanity check, I took my old MC and bench primed it: got fluid going in and out of both ports.

I'll install the new MC later today with a friend who's more mechanically inclined than myself. Hopefully we get the new one primed and then bleed the brakes. Updates will follow. And perhaps pictures, too!

 

[G_Squared]

I returned the refurb MC and bought a new one this morning. Bench primed it and it started pushing and pulling fluid through both ports. Because I don't have a proper shop with a vice, I simply held it level and steady on a table to bleed it. Installed that baby, reconnected the brake lines, and waited for my friend to help me bleed the lines.

We topped off the reservoir and started bleeding the brakes, starting at the farthest wheel, the right rear. My friend was underneath, watching the fluid come out while I pumped the brake. Not much air was introduced into the system because he didn't see a whole lot of bubbles coming out. Fortunately, my brakes were bled fairly recently so the ports at each wheel opened w/out any headaches.

Thanks to everyone who chimed in for this one. It feels great to get my baby running (and stopping!) again.