I am about to install a new master cylinder....previously, I have done MC replacements on a number of cars....Normally bench-bleed the MC via small hoses recirculating fluid up into the open top before installation...but the info on my new Fiero MC states "Let fluid drip out of pipe fittings, then pump MC to make sure it is working properly"

Which way do you guys go? (drip....fill...pour....what-EVer)

quote Originally posted by cvxjet: I am about to install a new master cylinder....previously, I have done MC replacements on a number of cars....Normally bench-bleed the MC via small hoses recirculating fluid up into the open top before installation...but the info on my new Fiero MC states "Let fluid drip out of pipe fittings, then pump MC to make sure it is working properly" Which way do you guys go? (drip....fill...pour....what-EVer)

The way I do it tends to be really, really slow.

I'll bench bleed it a little bit, to try to get as much in as I can, but I don't like brake fluid leaking out, so it usually doesn't work out very well.

In the end, I usually end up bleeding all of the calipers completely... which granted, is a lot of fluid. And a lot of it gets wasted. But I'll do the entire car. Just takes a while, but then you can be sure you've got all new fluid through the entire system. I just keep checking the reservoir to make sure it doesn't run low and suck more air into it.

quote cvxjet: Normally bench-bleed the MC via small hoses recirculating fluid up into the open top before installation.

IMHO

I always bench bleed a master cylinder by recirculating fluid with clear hoses which I can see the flow before the cylinder is installed in the vehicle.

After installed, I use a hand operated vacuum pump with a sealed container to bleed the brake system which to me is way easier than the 'gravity' method.

Other members may disagree.....

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Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles

quote Originally posted by Vintage-Nut: IMHO I always bench bleed a master cylinder by recirculating fluid with clear hoses which I can see the flow before the cylinder is installed in the vehicle. After installed, I use a hand operated vacuum pump with a sealed container to bleed the brake system which to me is way easier than the 'gravity' method. Other members may disagree.....

The gravity method has worked really well a couple of times, but the last few times I've tried it, it only ended up introducing more air in the system. Maybe Earth's gravity changed since last time I did it, but I ended up having to use a hand-pump to get the same results this last time. Haha...

Use small hose etc to keep fluid off of everything.
MC must be level to bleed it.
https://web.archive.org/web...ierocave/brakes3.htm

gav bleeding may not help for air in mc to combi valve tubes because not enough fluid volume to push air thru them.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

I bled the rear brakes and the fluid was moving 4 inches in tubing w/each pump....bled approx' 4 oz from each rear caliper to flush line.

Tried bleeding front brakes- fluid only moved 1/2" with each pump.....and always mainly air.....after 12 pumps, tightened bleeder screw and had assistant push peddle down- I could easily turn rotor.

I believe I may have a defective (Autozone-Chinese) MC....

I also tried vacuum bleeding with hand pump- basically, only air- and fluid is not moving out of MC....

What should I do as far as bleeding...?

quote cvxjet: I believe I may have a defective (Autozone-Chinese) MC I also tried vacuum bleeding with hand pump- basically, only air- and fluid is not moving out of MC What should I do as far as bleeding...?

Did you purge the master cylinder on the bench before installing it in the vehicle?
If so, did you push the cylinder to the end of each stroke to purge all the air?

If you saw that it was recirculating fluid in both the front and rear and removed all the air; I think your MC is good.....

A tip when using a hand operated vacuum pump to bleed the calipers:
Open the bleeder valve a full turn to allow more flow.

https://youtu.be/9p1-i1hCh14?si=_HWqvdplV9fiyCpY