Bleeding dual master cylinder brake system

[Michael Oritt]

There's been a lot of chatter on the Healey emailer list about dual master cylinder brake systems so I feel entitled to ask a question even if my particular problem is not Healey-related:

My Elva has a Tilton dual cylinder set up with drums all around, leading and trailing wheel cylinders on the front axle and single on the rear. Tilton in its instructions says: "If the vehicle has a dual master cylinder brake system then both systems must be bled simultaneously."

How do I do that? Must there be three people involved, one stamping on the brake with two others, one at each wheel, cracking bleed nuts "Simultaneously"? And what to do on the front wheels where there are two cylinders? Must each person wield two wrenches so that all four cylinders are opened, then closed during the time the assistant in the car is stepping on the pedal?

I feel I am missing something and will appreciate your experience.

 

[PeterC]

Michael, I think it's just a poor choice of words. I think they mean that you should be sure to bleed both systems rather than just one. I could imagine the whole balance thing not working. Don't you separate the masters when bleeding?

Peter

 

[Michael Oritt]

Peter--

I have received conflicting advice from folks whose opinions I highly respect--always a source of consternation! In any case, I proceeded to bleed the system as if it were a single MC system--right rear, left rear, right front then left front. I only had one assistant who did the brakes while I did the bleeders. In all cases the pedal was hard when stepped on, then went to the floor when the nut was opened and fluid expelled, etc. etc. At the end of the process the pedal was a bit harder and higher than when I commenced.

I don't know what kind of pedal setup the Healey folks who have twin MC's use. The Elva has a Tilton with balance bar if this makes any difference. In any case all seemed well both in the shop and on the final road test.

I'd really welcome comments here--if I did it wrong or if I am missing something I would rather learn it now and redo before next weekend's event.

 

[Keoke]

Sounds OK to me Michael since you were bleeding both systems at the same time. Provided, you expended enough fluid to make sure all the air was out of each system at each wheel.--Fwiw--Keoke

 

[Michael Oritt]

[ QUOTE ]
Sounds OK to me Michael since you were bleeding both systems at the same time. Provided, you expended enough fluid to make sure all the air was out of each system at each wheel.--Fwiw--Keoke

[/ QUOTE ]

Keoke--

I appreciate your input.

FWIW many folks on this forum and the Healey emailer list (I also posted the problem over there) seem to have different opinions regarding the meaning of the terms "Simultaneously" and "At the same time" and execution thereof. One person whose opinion I value highly has told me that indeed I needed to be doing a wheel cylinder in each system LITERALLY "at the same time". Another lister who has a Big Healey race car and an identical brake set up to mine says that he bleeds his car as if it had a single MC and has no problems.

I'm hoping to see some consensus if only for my own peace of mind....

 

[Dave Russell]

[ QUOTE ]
Another lister who has a Big Healey race car and an identical brake set up to mine says that he bleeds his car as if it had a single MC and has no problems.


[/ QUOTE ]
Yes -- Provided that the balance bar is set up correctly, which your's apparently is.
D

 

[Michael Oritt]

Yes -- Provided that the balance bar is set up correctly, which your's apparently is.
D

Whew--thanks Dave.

I'm gonna stop asking so many questions and get some rest.