Clutch slave cylinder and return spring

Technical advice Q&A

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265bhp
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#1 Clutch slave cylinder and return spring

Post by 265bhp » Sun Feb 28, 2021 8:33 pm

Hi all

Should the external mounted return spring on the slave cylinder return the piston in the slave cylinder all the way back into the body of the cylinder....having re done the seals to my main clutch master cylinder so it slides more easily and removed the seal within the slave...( and ensured they were well lubricated with fluid) the rod of the slave cylinder still can be manually levered back some way to its most compressed position

Is this normal...or have I missed a trick perhaps....can return springs loose their strength..( it looks reasonable...)

Help please

Thanks
Jonathan
1963 3.8 FHC ..now finished …………….
1974 2.7 Carrera now as an RS Touring

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mgcjag
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#2 Re: Clutch slave cylinder and return spring

Post by mgcjag » Mon Mar 01, 2021 8:28 am

Hi Jonathan......the service manual is vague in its description...but yes the pushrod should go fully in...this is the position it should be when you set the adjustment for the thrust clearance. ....so if it isnt fully retracted by the spring the clearance wont be there and the thrust will be in contact with the pressure plate......the spring position can be adjusted by repositioning its fixing bracket.....Steve
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc

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265bhp
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#3 Re: Clutch slave cylinder and return spring

Post by 265bhp » Mon Mar 01, 2021 10:49 pm

Hi Steve

Thanks for that...I had sort of suspected this would be the case..in which case I have a conundrum...as the pressure required to push the rod back in is definitely more than the spring can provide...which makes me think I have another issue

I guess I just need to take all the innards out of the slave cylinder and have another look
I am pretty sure the seals are in the right way..with sloping profiled and wider rubber profile facing towards the fluid...ie away from the push rod

The cylinders were re-sleeved win stainless and rebuilt in the early days of my restoration...and have sat waiting for the rest of the car...so I am wondering if they are gummed up somewhat....

Many thanks
Jonathan
1963 3.8 FHC ..now finished …………….
1974 2.7 Carrera now as an RS Touring

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#4 Re: Clutch slave cylinder and return spring

Post by mgcjag » Mon Mar 01, 2021 10:57 pm

Just loosen the bleed nipple...then see if it pushes in easily....use a bleed tube as fluid will come out....Steve
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc

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#5 Re: Clutch slave cylinder and return spring

Post by 265bhp » Tue Mar 02, 2021 10:08 pm

Interesting...thanks Steve...could be a rogue air bubble...
1963 3.8 FHC ..now finished …………….
1974 2.7 Carrera now as an RS Touring

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#6 Re: Clutch slave cylinder and return spring

Post by mgcjag » Tue Mar 02, 2021 10:41 pm

Hi Jonathan...i dont think its a rogue air bubble. ....just that opening the bleed nipple should allow you to push the piston in very easily...if it dosnt then you have a problem in the bore. .....Steve
Steve
69 S2 2+2 (just sold) ..Realm C type replica, 1960 xk150fhc

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Joes66
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#7 Re: Clutch slave cylinder and return spring

Post by Joes66 » Wed Mar 03, 2021 7:30 am

Why don't you just fit a new cylinder???
They are cheap to buy
I just don't see the point in fitting repair kits these days when new parts are widely available and so cheap it makes your eyes bleed
Back in the day say 30 to 40 years ago we used to fit repair kits because of un availability or cost
But thats all, you don't need to do that now
I mean....driving around in a 50 grand plus car with old brake parts just seems a bit mad to me
Joe
1969 series 2 2+2

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#8 Re: Clutch slave cylinder and return spring

Post by 265bhp » Wed Mar 03, 2021 8:06 pm

Joe

Slave cylinder was new..!....seemingly stiff after little use
As for the main cylinders I want the originals because of their casings..and with new stainless sleeves they are just as new as anything could be

All the best
Jonathan
1963 3.8 FHC ..now finished …………….
1974 2.7 Carrera now as an RS Touring

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#9 Re: Clutch slave cylinder and return spring

Post by Joes66 » Thu Mar 04, 2021 6:47 am

Fair enough!
Joe
1969 series 2 2+2

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#10 Re: Clutch slave cylinder and return spring

Post by 265bhp » Sat Mar 06, 2021 7:44 pm

Just to try and wrap this one up...I bought another seal kit and return spring from SNG this week and fitted.....

Spring seems better than the original...once I had a new one to compare to it was evident the original had stretched

The new seal seems to push in better than the last...although there was no visible difference.... :shrug: ...so after multiple bleeding sessions I now have a working scenario again...although the first press of the clutch pedal still doesn’t feel quite solid enough

Managed to take the car for a short drive up no down the lane again which cheered me up.... :bouncyyellow:
1963 3.8 FHC ..now finished …………….
1974 2.7 Carrera now as an RS Touring

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