Clutch Master Cylinder top up - thoughts

HarryM1BYT · 20th June 2010, 18:51

I have been thinking about this business of topping up the master cylinder for the clutch and the black diaphram in the top, which when you fit the top pushes out much of the fluid you top it up with. I have seen a suggestion to cut the lower part of the diaphram out, so it doesn't displace the fluid when you refit it.

I have an idea that when Rover built the cars, what they did was suck all of the air out of the diaphram so it takes up much less space in the cylinder and temporarily sealed the breather hole (tape), before refitting the top then releasing the air.

Has anyone already tried this method or have any comments on the liklehood of it working?

drewbie · 20th June 2010, 19:34

Quote:

Originally Posted by HarryM1BYT

I have been thinking about this business of topping up the master cylinder for the clutch and the black diaphram in the top, which when you fit the top pushes out much of the fluid you top it up with. I have seen a suggestion to cut the lower part of the diaphram out, so it doesn't displace the fluid when you refit it.

I have an idea that when Rover built the cars, what they did was suck all of the air out of the diaphram so it takes up much less space in the cylinder and temporarily sealed the breather hole (tape), before refitting the top then releasing the air.

Has anyone already tried this method or have any comments on the liklehood of it working?

Dont see quite where you're going with this. Ive replaced the diaphram with an o ring, end of problem.

T-Cut · 20th June 2010, 19:53

The master cylinder reservoir needn't be airtight if you intend to service it on a regular basis. The brake cylinder isn't. Of course the inaccessibility of the clutch master encouraged the designers to use a 'fit and forget design', which unfortunately didn't succeed all that well. In the original system, the diaphragm is supposed to expand and contract as fluid is moved from master to slave and back. All this while the fluid was hydraulically sealed in the reservoir. Removing the diaphragm is a good idea IMO. It allows more fluid to be put in the reservoir, which has to be a good thing. The replacement of the fluid every year or two along the lines of the brake system would also be good IMO and might mitigate against the compositional weakness of the sealing system.

I have already proposed the incorporation of a secondary reservoir to enable quick and easy servicing as per the brakes, but I don't think anyone's reported doing it yet. Here's what I mean.

The additional system need not be 'airtight'. It simply allows the original reservoir to be filled from under the bonnet.

TC

20th June 2010, 18:51	#1
HarryM1BYT This is my second home 75 Contemporary SE Mk II 2004 Man. Sal. CDTi 135ps, FBH on red diesel, WinCE6 DD Join Date: May 2010 Location: Leeds Posts: 17,273 Thanks: 2,160 Thanked 2,061 Times in 1,586 Posts	Clutch Master Cylinder top up - thoughts I have been thinking about this business of topping up the master cylinder for the clutch and the black diaphram in the top, which when you fit the top pushes out much of the fluid you top it up with. I have seen a suggestion to cut the lower part of the diaphram out, so it doesn't displace the fluid when you refit it. I have an idea that when Rover built the cars, what they did was suck all of the air out of the diaphram so it takes up much less space in the cylinder and temporarily sealed the breather hole (tape), before refitting the top then releasing the air. Has anyone already tried this method or have any comments on the liklehood of it working?

20th June 2010, 19:53	#3
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,753 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	The master cylinder reservoir needn't be airtight if you intend to service it on a regular basis. The brake cylinder isn't. Of course the inaccessibility of the clutch master encouraged the designers to use a 'fit and forget design', which unfortunately didn't succeed all that well. In the original system, the diaphragm is supposed to expand and contract as fluid is moved from master to slave and back. All this while the fluid was hydraulically sealed in the reservoir. Removing the diaphragm is a good idea IMO. It allows more fluid to be put in the reservoir, which has to be a good thing. The replacement of the fluid every year or two along the lines of the brake system would also be good IMO and might mitigate against the compositional weakness of the sealing system. I have already proposed the incorporation of a secondary reservoir to enable quick and easy servicing as per the brakes, but I don't think anyone's reported doing it yet. Here's what I mean. The additional system need not be 'airtight'. It simply allows the original reservoir to be filled from under the bonnet. TC Last edited by T-Cut; 20th June 2010 at 19:55..