Clutch master cylinder replacement question

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Clutch master cylinder replacement question

#1 Post by holty » Fri Feb 08, 2019 12:13 am

Hi All,

I replaced my clutch master cylinder today as it was slowly leaking and the previous owner told me it was on the cards. So I did a bit of research and apparently you can pre bleed the master and then bolt it on.

So I filled up the cylinder, pushed it in till no bubbles, bolted it up and attached the top metal part whilst fluid was coming out (as expected) and everything seems good as expected.

Just wanting to double check that I don’t need to bleed my whole system? I did do this weeks ago but with my old clutch master cylinder in place. Just don’t want to drive down the road and lose pressure on the clutch.



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Re: Clutch master cylinder replacement question

#2 Post by BAIT » Fri Feb 08, 2019 1:09 am

Yeah that works reasonably but you may have some air still in the system, if you've been driving for a week the air will be in the slave so you might be able to just crack the bleed nipple on the slave and gravity bleed to remove any remaining air. or better yet just get a mate to push the pedal and do it properly :D

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Re: Clutch master cylinder replacement question

#3 Post by Rota_Motor » Fri Feb 08, 2019 9:28 am

Usually it is not a bad idea to bleed the entire system to make sure the air is out, but if the clutch feels good, even if there is air in the system it won;t suddenly go bad unless something else fails.

Often, if the system is fully bled previously and you just change the master, there will be very little air trapped in the line right next to the master, if any. I'd probably rebleed it though, not hard to do on a rotor.

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Re: Clutch master cylinder replacement question

#4 Post by bumpstart » Sat Feb 09, 2019 10:24 am

yes it will need a bleed to make full reach reliably /one man bleed tool is less than 10 bux. takes a few minutes

for priming i have a second cap for the bowl.
it has an airline fitting in it and i use a maximum of 2 psi to push on the surface of the liquid and it will initiate a prime
similar you could fit a tyre valve stem the same and use the bike pump

for my hydraulic systems for the last 20 years i have filled it with my own blend of fluids and taken about 3mm off the back of the slave rod
it requires the above method to initiate a prime , once primed, works with a much more positive feel than the brake fluid
it can recover second hand parts that may previously have weeped, leaked or repeatedly failed against a heavy pressure plate with brake fluid medium
i went from replacing those hydraulic components every year . to no fails


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