Master Cylinders
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Joined: Dec 2001
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From: Tucson USA
Master Cylinders
I thought I had this all figured out - but noooooooo .... guess again.
okay I'm updating my braking system on my 56 with and ECI kit which uses F150 rotors and GM big car caliphers. To push the juice I am using a 70 vintage Mustang dual master cylinder for disc/drum brakes. So I have two questions:
Can you over drive a master cylinder when bench bleeding? I know it is possible when it is hooked to the pedal but it seems like it would be a little difficult when pushing the plunger in by hand. I'm not a 97 lb weakling but my prime years for strength was 25 years ago.
Second question, since the Mustang master cylinder has a 10 bls check valve built into the drum portion of the master cylinder, would this keep fluid from flowing out of that port of the master cylinder? This would make gravity bleeding impossible. A reliable source tells me the fluid should just flow out as it does the disc portion. But I'm on my third master cylinder and the fluid just does not trip out of the drum portion as it does the disc portion. I have to push plunger in to get any juice out of the drum portion.
So if the juice should be coming out of the drum portion, am I just the unlucky person who has wound up with three crappy master cylinders or back to my 1st question, could I be over driving these puppies when bench bleeding them and therefore screwing them up?
As always thanks for the help.
Rick
okay I'm updating my braking system on my 56 with and ECI kit which uses F150 rotors and GM big car caliphers. To push the juice I am using a 70 vintage Mustang dual master cylinder for disc/drum brakes. So I have two questions:
Can you over drive a master cylinder when bench bleeding? I know it is possible when it is hooked to the pedal but it seems like it would be a little difficult when pushing the plunger in by hand. I'm not a 97 lb weakling but my prime years for strength was 25 years ago.
Second question, since the Mustang master cylinder has a 10 bls check valve built into the drum portion of the master cylinder, would this keep fluid from flowing out of that port of the master cylinder? This would make gravity bleeding impossible. A reliable source tells me the fluid should just flow out as it does the disc portion. But I'm on my third master cylinder and the fluid just does not trip out of the drum portion as it does the disc portion. I have to push plunger in to get any juice out of the drum portion.
So if the juice should be coming out of the drum portion, am I just the unlucky person who has wound up with three crappy master cylinders or back to my 1st question, could I be over driving these puppies when bench bleeding them and therefore screwing them up?
As always thanks for the help.
Rick
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Joined: Apr 2002
Posts: 8,813
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From: Littleton, New Hampshire
Master Cylinders
[updated:LAST EDITED ON 20-Nov-02 AT 09:24 AM (EST)]Rick,
I don't think I understand what you mean by "over driving a master cylinder when bench bleeding", but it does make sense that you would get less fluid flow from the post with the 10 PSI residual valve than you would from the 2 PSI if the only force at play was gravity. Overcoming 10 PSI on a bench bleed would take very little pressure, however. The purpose of the 10 lb residual valve is to keep the brake shoes close to the drum and minimize pedal travel. The pads don't need as much, so 2 PSI does the job up front.
I don't think I understand what you mean by "over driving a master cylinder when bench bleeding", but it does make sense that you would get less fluid flow from the post with the 10 PSI residual valve than you would from the 2 PSI if the only force at play was gravity. Overcoming 10 PSI on a bench bleed would take very little pressure, however. The purpose of the 10 lb residual valve is to keep the brake shoes close to the drum and minimize pedal travel. The pads don't need as much, so 2 PSI does the job up front.
