Lotus Elan

Can clutch master cylinder affect heavy pedal?

PostPost by: M.J.S » Fri Aug 17, 2018 5:16 pm

My memory isn't as good as it used to be, but I don't recall the clutch on my +2 130/5 was especially heavy before I took it off the road 7 years ago for an engine rebuild that grew and grew and grew, hence the 7 years (and I'm sure many of you have been there!).

This week, now back on the road, I've had the pleasure of driving it again. I say pleasure, but the fact is the clutch is very heavy and makes a smooth getaway and slow speed manoeuvering tricky. The only thing that has been changed on the clutch is the master cylinder. The old one siezed whilst the car was stood so I had to replace it a couple of years ago as work continued.

Is it possible the new master cylinder is the culprit, has anyone experienced this? Is there a solution; smaller or larger bore? Recomendations appreciated.

Or is a very heavy clutch a common problem and I've simply forgotten how heavy it always was?

Thanks guys.
ZARDE the 130/5.
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PostPost by: Bigbaldybloke » Fri Aug 17, 2018 5:36 pm

Not all master cylinders are the same bore, you may have a different size then your original, have you checked the size of both of them?
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PostPost by: mbell » Fri Aug 17, 2018 5:50 pm

I'd second checking the master bore size as that is the item that has been changed. I believe it should be 5/8".

Heavy clutch pedal is common concern for the 130/5. Personally mine seems fine to me and not had any issues. There seems to be a few theories kicking around for why some are heavy and some aren't, from different pressure plates, hydraulic issues, to alignment of the clutch fork. I don't think there been a conclusive reason identified.

If your master is correctly sized I probably do a refresh of the hydraulics (slave rebuild, blow out of or replacement of pipes, fluid flush & bleed). If that didn't address it I try living with it and see if it improves with use as your looking at engine out to do anything else...
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
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PostPost by: normand » Fri Aug 17, 2018 8:44 pm

I suspect you have fitted a 3/4 " master cylinder which are plentiful on ebay, you need a 5/8" one which will give you a lighter pedal with extra travel but are a little more scarce, had the same trouble with my S4 . Hope this helps.
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PostPost by: JonB » Sat Aug 18, 2018 6:53 am

I have the same problem. 23 KG of force required to depress the clutch pedal. I've checked the master and slave cylinders and they are the correct bore. Was advised that the springs in the cover plate get stiff with age so have bought a NOS cover plate. Haven't swapped it yet (obviously an engine out job which I've been putting off!) but I have high hopes (which no doubt will be dashed as usual). The other thing is to fit a concentric slave cylinder off a Saab 900 but I haven't find anywhere that sells the required mounting plate.

If you find a fix please let us know!

Cheers
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PostPost by: Bigbaldybloke » Sat Aug 18, 2018 9:24 am

Hi Jon, I?ve just noticed that Kelvedon sell a complete kit of parts for the concentric clutch operating cylinder
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PostPost by: gjz30075 » Sat Aug 18, 2018 9:30 am

Could be as simple as the throwout bearing carring not riding smoothly on the
gearbox input shaft tube.
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PostPost by: JonB » Sat Aug 18, 2018 6:13 pm

Bigbaldybloke wrote:Hi Jon, I?ve just noticed that Kelvedon sell a complete kit of parts for the concentric clutch operating cylinder


Nice one, cheers!
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PostPost by: c.garde » Tue Aug 21, 2018 9:58 am

Hello gents and nerds,

Not to hijack the thread , but I think this Q. is relevant to the discussion re clutch MC.
I have tried to rise this Q some time ago, but nothing came out of it.
Have anybody experienced discoloring of the fluid with the presently available MCs ?
I have seen this problem discussed on both Miata and Mustang forums.

Just ranting: When my sprint 5gear was new I had great difficulties engaging the clutch.
An upgrade to 3/4 " solved the problem, clutch only marginally heavier. ( I must add: everything was to specs . )

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PostPost by: Bigbaldybloke » Tue Aug 21, 2018 1:30 pm

First question has to be what fluid are they using, could have a significant effect.
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