Vixen 2500 Clutch Hydraulics

[yosini]

Hi all,

I spent a very happy lunch break today under the Vixen, managed to change the slave cylinder without any issues. However, when it came to bleeding it there were constant air bubbles being introduced along the pipe from master cylinder (some clever PO had installed a transparent tube between master and slave - genius!). I eventually ran out of brake fluid to top up with so left it at that. Took it for a drive and much improved, I can actually select gears now! but the clutch biting point is still just off the end of the pedal's travel to the floor. There were three holes to put the clevis pin through at slave input shaft end, I went for middle - does this serve as the 'adjustment', it's a pretty heavy clutch too, especially in lunchtime traffic. At least I also managed to test out the cooling system - lots of traffic, central London, scorching day, fan over-ride on and kept happily around mid-gauge. Goody.

So, questions:
Do I need to replace the master cylinder too or look elsewhere for bubble generation?
Is there a clutch adjuster, or am I likely to need a new clutch plate too soon?

Cheers

Joe

[anonymous-user]

yosini said:

Hi all,

I spent a very happy lunch break today under the Vixen, managed to change the slave cylinder without any issues. However, when it came to bleeding it there were constant air bubbles being introduced along the pipe from master cylinder (some clever PO had installed a transparent tube between master and slave - genius!). I eventually ran out of brake fluid to top up with so left it at that. Took it for a drive and much improved, I can actually select gears now! but the clutch biting point is still just off the end of the pedal's travel to the floor. There were three holes to put the clevis pin through at slave input shaft end, I went for middle - does this serve as the 'adjustment', it's a pretty heavy clutch too, especially in lunchtime traffic. At least I also managed to test out the cooling system - lots of traffic, central London, scorching day, fan over-ride on and kept happily around mid-gauge. Goody.

So, questions:
Do I need to replace the master cylinder too or look elsewhere for bubble generation?
Is there a clutch adjuster, or am I likely to need a new clutch plate too soon?

Cheers

Joe

There is adjustment on the actuating rod from the slave to the clutch arm as you say. Firstly though with the air bubbles you need to look at the master cylinder as the culprit - if you change to a larger diameter master it will give less travel and be heavier. A smaller diameter will give you more travel and make the clutch lighter but there's a possibility it may bottom out.

Edited by V6Pushfit on Thursday 8th September 12:15

[plasticpig72]

Maybe that is why the clutch is heavy someone has fitted the wrong dia master cylinder or wrong dia slave. Sometimes different dia cylinders are not the same price so people make do with the cheaper one
Alan

[yosini]

Thanks - I'll start with the actuating rod and put the clevis pin through a different hole to see how that alters the pedal/clutch feel. The slave I replaced was a 1 inch unit and the master looks to be a similar bore, maybe I just have a weak leg....

Cheers

Joe

[anonymous-user]

yosini said:

Thanks - I'll start with the actuating rod and put the clevis pin through a different hole to see how that alters the pedal/clutch feel. The slave I replaced was a 1 inch unit and the master looks to be a similar bore, maybe I just have a weak leg....

Cheers

Joe

The master should have the size on the side - 1" is big.

[Dollyman1850]

Have you checked for crankshaft thrust? Clutch operation has been known to be affected on the straight 6 engine if the thrust washers have dropped into the sump. With the engine stopped have someone press the clutch and see if the crank pulley can be seen moving.

N.

[nwarner]

You didn't say if you replaced the transparent pipe or not. If not replace it with something that won't go soft like copper as when the engine gets hot the pipe will soften and when you press the clutch pedal it will expand so you won't get full movement of the clutch.

Nige

[yosini]

ah, there was me thinking the transparent pipe was clever allowing easy spotting of air bubbles....but yes, that makes a lot of sense. I've had a look on Rimmer Bros website and it looks as if there are two options for the Master cylinder bore - 0.75 and 0.7 inch - think I'll get a smaller one unless anyone foresees problems. I'll change the pipe out at the same time then too.

Thanks all

Joe

[anonymous-user]

I used 0.7" it works well and doesn't bottom out. More travel before clutch movement is complete though so you'll need to adjust the arm to suit it. Very light pedal I thought it wasn't working!

[phillpot]

yosini said:

there are two options for the Master cylinder bore - 0.75 and 0.7 inch - think I'll get a smaller one unless anyone foresees problems.

Don't you want bigger master cylinder / smaller slave to get more movement at the clutch release arm?

[plasticpig72]

The .7" dia sounds good to me. On Lotus Elans there can be a problem with flexible hoses in clutch line. Some owners use a one piece Goodridge/ Aeroquipe type line with good results. Rimmer Bros have a one piece Goodridge Hose 153671GR
Alan

Edited by plasticpig72 on Friday 9th September 13:38

[yosini]

Thanks Alan, that one piece hose looks good - do you know if that's the correct part number? ie is it long enough?

Cheers

Joe

[davidstacey42]

I had a problem bleeding the clutch circuit, air was rising to the highest point in the pipe and wouldn't bleed through. Solved it by disconnecting the actuator rod and pushing it back into the slave. That shoved the air back into the master cylinder. Clutch works a treat now.