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MG MGB Technical - clutch reverse bleed pressure

i have just replaced my clutch master and slave cylinders, i am going to reverse bleed it and just need to know what pressure i should use on my eazibleed kit, not sure if high pressure would cause a problem.


Why reverse bleed?. If you have pressure avaiable then bleed down. Incidentally I have seen a lot of cylinders fitted with the hose into the bleed nipple hole in the side of the cylinder & not the end!!!. It is much easier to catch the fluid below than out of the tank. Do not use more than 20psi or you risk blowing up the tank.
Garth Bagnall

Very light, I reduce tyre pressure to about 10lb, i.e. even less than if it is screwed onto the master.

But you don't need to use an EeziBleed (which was the way I first reverse-bled), just connect a tube from the right-hand caliper nipple to the clutch slave nipple, open both, and operate the brake pedal very slowly and carefully (or it will blow the tube off). Even with the single-circuit metal can brake master there should be more than enough fluid to fill the clutch master just past the top of the cylinder, then top off both as normal, but keep a close eye on brake master level in any case. With the plastic dual master you probably won't even notice the change in level.

Why reverse bleed? Have you not read the zillions of tales of woe when trying to bleed top down, regardless of whether you use an EeziBleed or not? Having seen those I've never done anything else and it only takes moments.
Paul Hunt 2010

I use the E-Z Bleed with 15 lbs. of pressure, from the top with no problems. It usually takes less than ten minutes. RAY
rjm RAY

However you choose to bleed, be sure to push the slave cylinder piston in as far as it will go before you get started. -G.
Glenn G

I don't like doing that. For a start you have to clamp it in as it will work itself out again from the spring that is inside. Secondly when you do release it after bleeding it will be trying to pull fluid down the hose, pipe and through the master cylinder via a tiny hole from the reservoir i.e. quite some resistance. The seal isn't designed to pull but be pushed, and it is likely to suck air in ruining the bleed. It shouldn't need it. People claim that there is an air bubble trapped at the top of the slave even when you bleed top-down. Some after-market units may, but OE don't, the bleed hole is drilled across the top of the angle where the end meets the cylinder wall, and is the highest point. The cylinder is also tilted slightly so that is the highest point of the cylinder wall anyway, and the only way you could defeat that is if the rear of the car was raised significantly higher from the front for some reason. In theory there will be a bubble trapped with top-down bleeding as the hose is lower than the nipple, but if there is it hasn't caused me a problem.
Paul Hunt 2010

For the rcord, just did mine after changing both master & slave seals, used an ezbleed for the 1st time ever, bleed was perfect after opening the nipple wide enough. Used my pushbike as it's easy to refill the tyres with a pump! It looked like it may not work at first but the pressure cleaned out some rubbish that was lying in the lines as well!
P M Gregory

This thread was discussed between 25/04/2010 and 04/05/2010

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