Duratec hydraulic clutch issues

[Jimmythedimmy]

I have recently moved from a 7.25 inch to a 8.5 inch clutch on the duratec and after a slight mishap with the spacing have finally got it working (ish). My issue is that the clutch only seems to fully release when the pedal is properly pressed all the way to the floor. If not the revs hang whilst changing gear. I am currently running a retroford bellhousing with a RWD motorsport clutch and flywheel and the retroford mondeo sourced clutch release bearing. The master cylinder is a girling .625 on a gartrac bias pedal box.

Am I right in thinking a larger bore of master cylinder would move more fluid and therefore more distance on the clutch release bearing for a given pedal movement? If so what size should I go for .650 or .700? any have any experience with this?

Thanks in advance for any help you can give me.

[Graham]

yes a bigger master would move more fluid, which might solve your problem, as long as it does not over extend the slave which will kill it! if it almost works i would increase the slave size by the smallest amount, especially given that it will make the pedal heavier

[Jimmythedimmy]

Thanks graham, I will give a .700 a try, having just looked I seemed to have made up the .650 option.

[Jimmythedimmy]

So, a quick update on this. I decided to check that it wasn’t air in the lines so bled the system today. I thought I would film the issue to see if you guys might know what it was before I possibly go down the wrong route with the master cylinder. Which I have ready to fit (just in case).

Here are the two videos. One is the car in neutral and just giving a quick rev. The other is the car in neutral and the clutch fully depressed and revving once again.

https://youtu.be/5nToSZkdDUc

https://youtu.be/pDfW_OgQ9Xc

Any help would be greatly appreciated.

[katana]

yes a bigger master would move more fluid, which might solve your problem, as long as it does not over extend the slave which will kill it! if it almost works i would increase the slave size by the smallest amount, especially given that it will make the pedal heavier

G - I think you mean Master? The Slaves are pretty much one size fits all. Incidentally, if possible, a smaller slave would lengthen the pedal. And yes, a 0.65" master is a fantasy size LOL!

[Graham]

G - I think you mean Master? The Slaves are pretty much one size fits all. Incidentally, if possible, a smaller slave would lengthen the pedal. And yes, a 0.65" master is a fantasy size LOL!

yes i said both master and slave, in both cases i meant master

[Jimmythedimmy]

I fitted the .700 master cylinder and as expected it raised the biting point significantly. However it still feels like the revs hang when the clutch is depressed. I made a couple of videos for you guys to see what I mean. I am really confused now and do not know what the next step is.

https://youtu.be/lIeFUXP5zu4

https://youtu.be/4Ix584F3Zm0

Is this normal? are the fingers on the clutch somehow not returning the slave quick enough? Any help would be greatly appreciated.

James

[Leafy]

Sounds fine, looks like your tach is sticky.

[Jimmythedimmy]

Found the issue, in the end it was the simplest of solutions, the throttle cable was a little sticky and engaging the clutch was enough movement on the pedal box to slow the return of the pedal. Causing the revs to hang, now fixed and working fine.

[Jimmythedimmy]

Took the car out on a trackday in Zolder too, was great fun.

[Forest_rallying]

Nice car Jimmy!