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Sprite MK III combined master cylinder issue

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JimLaney

JimLaney

Senior Member
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15 years ago my MK III was undergoing rebuild. The build stopped and no fluids were ever added. I bought it recently and have started over. Yesterday I removed the pedals and the master cylinder for a re-do... cleaned up outside, removed push rods, pins, and exterior boots. The interior plunger, spring, sup will not budge. It sits soaking in DOT 4 but I'm not optimistic that they will come out. Any trick or is it a replacement issue?

If replacement, should I go with update to independent reservoirs for clutch and brakes or replace as is...?

hydraulic reservior.jpgI
 
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Compressed air into the ports may work. Do not stand in front. If they come out the problem is that you will most likely have some pitting where the rubber was touching for all these years without moving.
You can try to hone out any pits but the best bet is to send the cylinder to Gerard to have the bores re sleeved.
 
There is a good chance that they are rusted up. Depending on where they are stuck you may be able to use pressure to free them. Either from a air compressor or a grease gun. All sort of precautions should be taken to avoid dangerous projectile pistons.

I ran a stock unit on my Sprite for several years. I just removed it last week to install a custom triple cylinder setup. Only once did I have an issue. The clutch stopped working due to a sliver of foil from a bottle seal. However, I always feared that the clutch slave would leak on a long drive and suddenly I'd be without brakes at the end of a two hour drive. Never happened ... but was always in the back of my mind.
 
I should add that if you decide you need to replace it I can sell you mine. It was from the first batch that Gerard had made. It is 3/4" both sides.
 
The Sprite IV came with separate clutch and master cylinders, so a switch is certainly feasible. If you want to go that way, I can send you pics of how it's set up on mine.
 
Jim,
There are several ways to address your MCs and I decided to go with a sleeved original from Sierra instead of the one I have pictured. The pictured MC is a pair of Tiltons and they work very well...you can even modify your pedal box for 3 MCs with a bias bar for the brakes as well as a residual valve. You can even go with a Tilton pedal box with any combination of MCs to suit your particular needs.
Rut
 

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There is nothing wrong with the single line system, BTW. I've had several brake failures in my life and one with a single line Spridget. All failures have given me a warning and in the case of the Spridget, the hand brake is very good. Limped home from city traffic 30 miles away. In that case PO had bent a line so that the drive shaft rubbed through it inside the tunnel.

Kurt.
 
There is a ridge in the dual master so that if you loose the clutch or brake circuit there is enough fluid in the reservoir to get you home.
 
I can see that Joe ... but what if it sloshed over? I guess I'm just paranoid.
 
Trevor, when I lost my brakes I still did have a clutch all the way home. I also had a clutch failure once with the slave piston being pushed out so no fluid down to the partition. In that case I had brakes all the way home. 50 miles in that case. Got lucky so that after a push start I could double clutch to shift and fortunately didn't have to stop at any of the stop sign's.

Kurt.
 
Correction....no double clutching without a clutch!:friendly_wink: Matched revs to shift!

Kurt
 
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