Made up a master cylinder pump to replace my old grease gun version.

Only problem is it seems to take forever to build up initial pressure. Takes heaps of deliberate pumps waiting a second between each and eventually you can see the back pressure rise on the gauge with each stroke. Then it gets to a point where the pressure reaches a level where it becomes suddenly more efficient with each stroke esp as it approaches the more normal range.

I'm wondering how I can make it more efficient especially the initial pumping period. Perhaps adding a one way valve in the hose to assist the shrader valve? Or are the hoses too long and/or flexible. They are 500psi hose.

The master cylinder holds up fine. I can open up the system too it and there is no backleaking.

Open to any suggestions please. Cheers






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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

I use a brake master cylinder too, but I stuck with the tin can - I built it at in desperation at 1 o'clock in the morning a few years ago and it kept working...

I do have a 1 way valve and a tap in the line

I make sure the hose has no air in it before attaching it to the car, then screw in the centre of the schraeder chuck to pressurise the hose, and I use the tap to release a bit from the system and push any air out of the line, then start pumping

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did I tell you that I won a trophy?

What Simon said. I use a clutch MC.
Mine has no tap or air chuck, it is 2 front brake hoses joined by a clutch steel line. Homemade brass fitting with a schrader thread inside.
I purge it before screwing on, then tighten the pipe nut.
Only maintenance in 20 years has been 1 set of seals in the MC.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

The factory pump is very slow to build up pressure from "completely empty" too. Each stroke causes the gauge to go up, then fall back to almost the same position it started. Then it begins to build pressure.
I think that is a characteristic of the system and not your pump.

It's a good idea to fill the bag with fluid before fitting. Otherwise you are compressing a heap of air inside the bag.
I used a tiny funnel attached to a cartridge nozzle. Tie the hose up so it's vertical.
Takes a little while, but it's worth it.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Thanks.

Regarding bleeding, yes I do the same and try and ensure all the air is out of the hose, even tried letting the fluid come back through the cylinder until no bubbles.

Perhaps I'll try a one way valve close to the top of the MC, to help out the Schrader valve.

I'm just finding it seems to be a ridiculous amount of pumping if say the car is down to bump stops but not empty. Almost feels like nothing is happening.

I'm just thinking that with that length of hose with its slight give, plus the gauge, I'm losing a bit of efficiency with each pump.


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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

Could be the Schrader valve is leaking. It is a one way valve, provided you don't hold the pin in.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I use a clutch m/c with a ball valve in the pressure line. Open the ball valve as i pump into the suspension, close the ball valve at the end of the master cylinder stroke. Sounds complicated but easy with a bit of practice.