Dual Master Cylinder

[monocoque]

I put a Dual Master Cylinder on my newly restored Towd and have not been able to get the front brakes to engage at all. I have adjusted the shoes up but it seems as though I cannot feel the second piston being engaged when i push the pedal down. THe shoes, wheel cylinders, brake lines rubber lines et al are brand new. THe only old thing on the brakes are is the pedal cluster. I am using an old pedal cluster(restored). Could it be that the Plunger rod is an old style and not long enough for use with the later dual master cylinder? OR could it be that the second piston is jammed in place? I have bled the brakes and get a decent flow of fluid from all wheels while bleeding. Any thoughts? Thanks Chris

[newmanx59]

Chris, Do you have any play between the pedal pushrod and the master cylinder? If the rod doesn't have freeplay, it will not allow the piston to return fully and the fluid transfer port will never open up to allow fluid to the wheel. What master cylinder are you using?

[jsturtlebuggy]

Did you bench bleed the M/C before putting it on the car? I have also had a brand new one that was bad. Pedal was always spongy until changing it.

[Gene-C]

Chris, sure sounds like an internal leak in the MC! 1 the "piston[s]" are actually one piece 2 You have fluid flow when bleeding [no pressure buildup] Exchange the MC!

[monocoque]

I am not sure what part number the master cylinder is. I bought it from a foreign car shop. It is for late model Beetles..so it is a dual master cylinder. I have put the Rabbit reservoir on it and I have no leakage around the reservoir when it is filled up. I did not bench bleed the MC before putting it in place...I never have done that and have always been able to get a good pedal in the past. How do you bench bleed one? ANother question..have you ever had the brake system work but when you push the pedal down it feels like it is bottoming out but is no where near the end of its throw? Wacky questions for wacky times... Thanks Chris

[Lee]

Chris, Make sure you don't have a master cylinder for a Super Beetle (if you have Standard Beetle brakes). Just tossing out ideas...

[jsturtlebuggy]

Bench bleeding is simple. Just put the m/c in a vice ( clamp the vice to one of the bolt tabs). Put fluid in the top ports and push on the piston with a punch, philips screwdriver or what ever you have. You are seeing if fluid come out of the ports where the lines attach. Sometime you have to put your finger over the outlet ports on the when letting the piston return to create a suction on the inlet ports. I would check your brake pedal push rod freeplay. Super bug m/c has different bolt pattern. How old are the brake hoses? You may have one that is swollen closed.

[Gene-C]

Part #s for Master Cylinders: 113 611 021C M.C. thru 1964 German 113 611 021CBR M.C. thru 1964 Brazilian 113 611 023B M.C. 1965-1966 German 113 611 023BBR M.C. 1965-1966 Brazilian 113 611 017K M.C. 1967-1977 Bug ( not super beetle) Brazilian 113 611 017KGR same as above German :2cents: Jim,bo

[Gene-C]

Hello Chris, I have been fighting w/ my dual master cylinder also. My problem is I can not get free play and good braking at the same time. When I adjust correct pedal free play, my pedal goes to the floor IE: NO BRAKES. When I adjust the plunger rod longer I get good braking action, but sometimes the brake lights come on and stay on without stepping on the brake pedal. When I welded in the new brazilian floor pans, I noticed the nutsert for the pedal cluster stop was in a different location. I fabricated an adjustable pedal stop. You asked if the old and new plunger rods are the same size? Yes. I compared the 1962 and 1976. Identical. I own a 1976 bug that came stock from the factory w/ a dual m/c and four wheel drum. I did not bench bleed my m/c. But I have bled the m/c after installation (on the manx) I have driven my manx about 1000 miles with the new duel m/c. But with no free play and occasionally the brake lights stay on. I think 5 things must be adjusted properly: 1. Pedal stop. 2. Plunger rod. 3. Free play. 4.Brakes. 5. E-brake. I am still searching for the perfect set-up myself. Every componet in my brake system is new. The only change I made was I installed a 1976 pedal cluster. The 1962 and 1976 Pedal clusters appear to be identical. The attachment point for the Plunger rod to the brake pedal appears to be in the same location on both pedal clusters. If you want to talk on the phone, my e-mail is shredder1000@juno.com