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Dual Line Master Cylinder

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jcatnite

jcatnite

Jedi Knight
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Hey guys, need some quick advice. My master cylinder in the 76 Midget decided to go ahead and allow fluid to leak down the brake pedal which puddles nicely on the new floor mat. Nothing spectacular happed with the brakes as of late so I'm not sure why it decided to let go. Anyway, I thought I would rebuild it and after the long process of getting a rebuild kit from the local chain parts house... I pulled the master cylinder and it is stamped on the bottom "oversized kits only" bummer. I'm too cheap to give up in the middle of winter and shell out $250 for a new one. I seem to remember someone adapting a later American master cylinder to a dual line system with some plunger modifications. I've searched and searched but can't find it. Does anyone remember who did this or what the application was for the donor cylinder? I have limited access to a small machine shop so fabing up a plunger of the proper length wouldn't be too difficult. Or if someone has a decent dual line they would like to get rid of pm me please.
JC
 
Why not exchange the kit for an "over-sized" one which would be cheaper than switching cylinders? Check with Tony Barnhill as to the availability, if anyone can find one, he probably could!
 
Not opposed to that. I figured that at some point it was "oversized" by an unknown company and oversized could mean one of a variety of sizes. I dug in a bit to get a look at the seals (since the pedal was solid) but couldn't get past the first teflon ring without jumping in feet first. Thought I would back out and regroup to see where it took me. The master cylinder says "Fenco" on the tag where it is marked as oversized.
JC
 
My totally rebuilt Apple Hydraulics master cylinder is leaking like a sieve. I am sending back to them as there are clearly some rebuild issues so I will hopefully get a working one shortly. But as I did research I found that the mechanical design of the dual unit is pretty suspect. As such, I would consider an aftermarket or performance master, and this thread seemed timely. Can anyone recommend a plug and play system? I am way beyond the point of making any mods or structural changes...Thanks
 
Mustafa, I do not know of any "plug and play" alternatives. Short of major modification to switch to a system out of a newer car, or other surgery to adapt an after-market set-up we are stuck. Did you use the right fluid, since Apple warns of rubber cup failures with the wrong fluid? They recommend not using silicone fluid, but I have used it without cup failure problems, though leaks with the dual master system are a problem! I have thought about doing a search to find cups of the right rubber/synthetic compound to prevent this problem!
 
Mike,

Thanks for the reply. Yes, I am using Castrol GLMA (non-synthetic). The leaks are from the gasket in the front and top. Very frustrating!

I know of one "plug and play" (I think-pretty sure no mods are required but I could be wrong) and that is the unit that Tom at Speedwell makes:

https://www.speedwellengineering.com/brakepage.html

I think it fits in--you would have to modify some of the lines in and out, and add external reservoirs...

Mustafa
 
OK Mustafa, you are looking at the newer setup. I was thinkig about the dual cylinder as found on the Bugeye! The VERY expensive alternative is the sebringsprite one Trevor has above, that will fit in the Bugeye pedal box! An elegant solution, but pricey!! The speedwell setup will require some cutting and modifying to the pedal-box area on a Bugeye. If you are going to do that, a less expensive way would be to adapt a stock one off a newer Sprite/Midget!
 
That's a good deal if you only need the cylinders - it is for a '73 though!
 
You might take a look at the dual masters in the 70's Datsuns. They started out with 11/16" bores, then to 3/4" and 7/8" in the 240Z's. With a bit of effort they take a remote inlet from tilton or wilwood. hole spacing is a bit off but can be made to work. The threads are 10mm. Just a thought...
 
Wow bud, that's worth a try. I was unable to source a "oversized" rebuild kit but I remembered you saying there was a $50 master cylinder on RockAuto way back a while ago. I checked the items for a 76 but never considered looking on an older application. I ordered one and still have my leaking one so between the two I'll have something anyway. I was considering letting a forementioned hydraulics shop rebuild the one I have but I really need to totally go through the system before spending large dollars on the system. I plan to repipe the entire system when I strip the tub but right now I'm still rolling through the restoration trying to sort out the mechanicals. I did spring for a Weber a while back. I'm now in the process of bending my some 1 7/8" tubing to put on for the exhaust. Thanks for the great find. I'll let you know in a few days if they really have them and if they are any good. I know that I remember reading where someone put a master cylinder from a more modern car on their spridget but can't for the life of me find it now.
Thanks again,
JC
JC
 
I rebuilt my master. It was a total bear of a job that took a week (not full time) and required making a JESUS! clip remover because I could not find an off the shelf one that would work.


And now my new rebuilt master leaks. What a bummer!

Please report back on the Rock Auto unit when/if you get it.
 
Also check White Post for rebuilding.

https://www.whitepost.com/


I think you will find that Whitepost brings all the specs back to factory tolarance and replaces all the pistons even with their own brass units along with resleaveing the cylinders. In fact a super nice job.

I have used two from them over a 30 year or so period. Both worked as advertised.
 
I knew by rebuilding my own, it would only be a stopgap measure until I replaced the entire braking system anyway. I know when it went down, thinking back on it. When I compressed the calipers to reinstall them after the front suspension rebuild last summer, I noticed rubber bits in the reservior. I remember thinking then that it wouldn't be long but it lasted longer than I thought it would. I was surprised to see what actually came out of the body of the old master. It is pretty nasty stuff that you would expect to find in a sewer not in a hydraulic system. I don't think it would be salvagable without a resleeve but the weird thing is I totally had awesome brakes and a solid pedal. I was waiting for the pedal to start drifting down and was really surprised when my shoe slid around in brake fluid instead...
JC
 
Quick note for those who might be interested. Rock Auto is fresh out of the "$50" master cylinders. I figured it was a long shot but at that price one worth taking. Wasn't really ready to go through the brakes yet but seems like it may be time to bite the bullet and repipe the system, replace the master cylinder and rebuild the calipers. I had planned to wait till I stripped the tub for the major restoration but looks like it will be sooner rather than later.
JC
 
I could of swore I read about a year ago that silicone fluid was the way to go. I will be sending my dual to whitepost soon for a rebuild but have already redone all my brakes and used silicone to put my front disks back together and currently have silicone in them. What is the best way to remove this or will just draining the piston cavities on the front suffice?
 
JC, I got a 73 Midget race car, that has good M/C on it. I'm going to get rid of this m/c and pedal set-up and do a Tilton pedal/M/C set up. I rebuilt the cylinder a year ago and have raced the car three times, it works perfectly. I'll sell it for less than half what a new one cost including the resevoir and throw the pedal assembly in if you want them. call me or email if you are interested, my contact info is listed on the website below. Here's a picture of the cylinder I'm getting rid of in the car.
 

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