Lotus Elan

Clutch oddities.

PostPost by: JohnMorin » Mon Jul 10, 2023 3:19 pm

Hi

I have overhauled the clutch hydraulics on my 1969 S4. I can not get the clutch to disengage. The master cylinder has had a repair kit and the slave cylinder is new and the correct 7/8 bore. When all put back together and bled the clutch pedal sits much lower than the brake pedal. I got someone to operate the clutch while I watched at the gearbox end and the clutch fork only seems to be moving about 1/2 inch, is this enough?

1. What could cause the clutch pedal height to be incorrect given that it is the original push rod and master cylinder, if I pull the rubber cover off where the push rod goes in I can see the piston is right at the pedal end of the bore.

2. Does anyone know what the clutch for travel should be?

Thanks

John
1969 Elan S4 FHC, purchased in 1978, now with a big valve engine.
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PostPost by: MartinH » Tue Jul 11, 2023 8:26 am

I think I just had the same experience with a new clutch slave cylinder. In the end I noticed that the piston in the new cylinder was shorter than the original. My fix was to put the seals from the new piston onto the old one and put it back into the slave body. It worked fine once back in place.

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PostPost by: JohnMorin » Tue Jul 11, 2023 1:24 pm

Thanks for the response.

Problem solved - partially - I made the push rod adjustable, it was about 10 mm too short, do you know how much too short your piston was? The other issue was caused by air in the system and maladjustment of the slave cylinder push rod. With a 5/8 bore master cylinder and 1 inch of travel, which is what I measured, it works out to about 1/2 inch travel at the slave cylinder. Once I got the pedal to pressurise I was able to set the slave cylinder push rod to the correct clearance, I was then able to engage gears. However, if I leave the car for a few minutes the pedal goes soft and I have to pump it up to engage gears. There's still air in there so the next task is to figure out how to get it out, using the normal bleeding procedure as per brakes is extremely difficult due to the location of the slave cylinder so it's very difficult to tighten the nipple in one go which is how I suspect the air gets back in.

John
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PostPost by: mbell » Tue Jul 11, 2023 6:16 pm

JohnMorin wrote:There's still air in there so the next task is to figure out how to get it out, using the normal bleeding procedure as per brakes is extremely difficult due to the location of the slave cylinder so it's very difficult to tighten the nipple in one go which is how I suspect the air gets back in.


I normally just use a length of wood to wedge the clutch pedal down and leave it a day or too. I am not 100% sure how this works but the remaining air seems to escape the system leaving it full bleed with no messing around.
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PostPost by: gjz30075 » Tue Jul 11, 2023 7:50 pm

John, I extended my clutch bleeder nipple with a braided line and ran it rearward. Access is
very easy now. Check this thread.
viewtopic.php?f=37&t=24366
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PostPost by: JohnMorin » Wed Jul 12, 2023 7:03 am

Thanks for your responses.

I'll try the piece of wood holding the clutch pedal down.

I looked on the net for a remote bleed solution but couldn't find one ready made, I'll look into making one up using the info in the post.

Thanks again

John.
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PostPost by: smo17003 » Wed Jul 12, 2023 10:06 am

John,

I did this job earlier this year. Parts were from Car Builder Solutions - carbuilder.com

I used:
PSBF30 - 3/8" UNF bulkhead bleed nipple
PSBF08 - 90 degree swivel
PTFEHO - braided hose
BUOLIVE - a spare olive, just in case you mess up assembling the parts.

I routed it up on to the bulkhead, and secured with a P Clip. The hose comes by the metre so you cut to your required length.

Mike
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PostPost by: The Veg » Thu Jul 13, 2023 1:39 am

I ran my remote bleed line up the firewall, the direction that air bubbles will want to go, and saving me having to get under the car to bleed the clutch.
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PostPost by: JohnMorin » Fri Aug 04, 2023 9:58 am

OK

Wedging the pedal down with a piece of wood and leaving it for a couple of days didn't work, thanks for the suggestion anyway.

I made a remote bleeder and it's mounted on the bulkhead on the passenger side. It certainly makes bleeding easier but still no joy.

Next I borrowed a pressure bleeder from a friendly mechanic but that just sprayed fluid out from under the cap.

Finally I bought a new master cylinder although the push rod was far too short, even shorter than my original. Swapped it for my adjustable one and with a three man team, one operating the pedal another topping the fluid up and me at the nipple end after 30 cycles of open nipple pedal down and hold, tighten nipple and pedal up I finally have a working clutch.

I have never known so much difficulty bleeding a clutch, I hope I don't have to do it again!

John
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