Is bench bleeding a new Master Cylinder Necessary?

monk302 · Apr 7, 2004

I am putting in my master cylinder with the Granada swap and I was wondering if bench bleeding a MC is necessary. To me it seems kind of unnecessary. You route the hoses into both of the bowls fill the MC with fluid, and then push in the plunger in several times with a dowel until there is no more air. Then after the air is out you have to unhook the rubber hoses, mount the MC on the firewall, and then put on the brake lines all the while air is no reentering the MC since you have just unhooked the previously bench bled MC.

What is the point to bench bleed, get all the air out, then mount the MC up to the firewall while air is now reentering. It says that the warranty will be void if it is not bench bled but to me it just seems a way to cover themselves.

Now that I have bench bled the MC should I just put it to the firewall and hook up the brakelines and then bleed the entire brake system. That seems to me the only way to get all the air out of the system.

Thanks

Ronstang · Apr 7, 2004

If you don'y bench bleed a master cylinder you stand a chance of not being able to get the unit to prime enough to ever begin pumping....then you end up bench bleeding it in the car and making a huge mess you could have avoided by using the BENCH in the first place.

You can simply open one of the bleeders on a caliper now and pump until you get fluid into the caliper, then do the other and once both calipers have fluid in them bleed the system in the normal manner.....pump, hold, bleed, release pedal, and repeat. This will get all the air out of the system in pretty quick order. I just did it exctly this way on Sunday doing a Granada swap for a friend and it was effortless and without incident.

gingerbreadman · Apr 7, 2004

iv always wondered the same thing for the fact that when you have a leaky wheel cylander and run the M/C dry its pretty much like not bench bleeding it when you pour more fluid in and bleed the system....

but man just save yourself the trouble and bench bleed it... every m/c iv scene has come with a bench bleed kit and that costs companys money, they wouldnt spend any extra money unless they had to...

-gbm-

kcp203 · Apr 8, 2004

gingerbreadman said:
iv always wondered the same thing for the fact that when you have a leaky wheel cylander and run the M/C dry its pretty much like not bench bleeding it when you pour more fluid in and bleed the system....

-gbm-

That's why they tell you to bench bleed the MC if it ever does run dry. Breaks are pretty much the only thing that you really can't afford to take a chance on, so I've never really thought about not following the directions.

Ozsum67 · Apr 8, 2004

It's usefull, but not absolutely nessasary. You could always push the air through 40 some feet of brake line.

dodgestang · Apr 8, 2004

You can bolt the master cylinder up into the car fill it with fluid, hook up the little hoses and feed it back into itself while installed on the car....after the air bubbles stop coming then you can just connect the lines and bleed the system.

This is essentially bench bleeding but you bolted it into the car. This is useful for people that do not have a vise or some other means to clamp the MC in an upright posistion and fill it with fluid. Just be careful because brake fluid will eat paint.

HistoricMustang · Apr 9, 2004

For what it is worth, I have never done it.

HistoricMustang
www.historicmustang.com

2nd Mustang · Apr 9, 2004

When I replaced my MC, I did it the lazy man's way. Loosened the lines at the MC one at a time and had my son pump the pedal a few times. Make sure you have something to soak up the mess as brake fluid is a really good paint stripper.

67CoupeDriva · Apr 9, 2004

I didn't the last time I put a new one in, and it took about 6 months and bleeding the brakes every other weekend for me to get a firm pedal.

I just did it again with my disc brake conversion and did bench bleed it. I will never fail to bench bleed again!!

Is bench bleeding a new Master Cylinder Necessary?

monk302

Ronstang

New Member

gingerbreadman

Only half-baked

kcp203

Ozsum67

Too much thin air

dodgestang

Active Member

HistoricMustang

Active Member

2nd Mustang

67CoupeDriva

Member

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Is bench bleeding a new Master Cylinder Necessary?

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