clutch not disengaging

[iainbja]

having an issue with my Spitfire clutch. In 2017 I fitted a 1500 engine to my mark 4 spitfire. It has J type overdrive with the earlier box the one you can change all the gear lever bushes etc not the later 1500 Marina gearbox.  to make this all work I needed a think 9 spline clutch to fit my gearbox and the 1500 cover. There was this configuration in America in 1974 so that's what I got plus a new slave cylinder. It has been fine however i always felt like i could do with being able to press the pedal further into the floor. I made sure no carpet etc getting in the way I even ground some of the slave cylinder face away so it fits closer to the gearbox so the rod pushes slightly further.

However yesterday it started to get worse so grating into reverse but forward gears ok but gradually detreated until now car jumps forward with the clutch in and really is not drivable I amnged the 30 miles to get it home.  Any ideas do you think slave Cylinder or master or clutch no fluid leaks i can see although clutch fluid dropped about 10 mm since I last looked.  

 

 

[Clive]

I would start by bleeding the clutch. 

And check for free play in the system. A little wear in the linkages all adds up. But equally the  mater/slave could be playing games. With the tunnel off you can check the operation (do so before bleeding as well)

[johny]

Yes the fluid loss could be something as well so remove the rubber covers and check where the push rod goes into the master cylinder. Any leak here often runs down inside the cabin where it can disappear into the carpets... 

[Pete Lewis]

is the bleed in the top hole above the supply pipe ???

i would pull the slave out  check for seapage, if you can leave it connected push the slave piston fully back to reduce the volume and try a bleed 

before refitting , see other posts about adding a pipe or brake flex to devise a remote bleeder saves all the access problems 

often done by buy a flexible feed pipe and use old as the bleeder witha fixed nipple idea 

just to add check the throwout pivot pin is not trying to escape  out of the clutch housing 

Pete

 

[iainbja]

taken the slave cylinder from underneath ordered a new one it did look ok though but it was bit wet down there so maybe a tiny leak.  I could do with a longer shaft on the master cylinder to improve how far it deploys.  I di change the foot pedal because it had gone a bit oval and fitted a new sleeve where the pin goes through.     

[Pete Lewis]

all good stuff  ........to add 

there should be plenty of travel room in the cyl for tthe piston to take up any travel in its lifespan of wearing and as the disc wears the piston gets pushed back further 

as the disc wears the diaphragm fingers extend rearwards pushing the piston up the slave .

Pete

[Nick Jones]

11 hours ago, Pete Lewis said:

just to add check the throwout pivot pin is not trying to escape  out of the clutch housing

This…..

[Pete Lewis]

Nick youre on blankety blank   Ha

Pete

[PeteH]

Something to consider?. Hydraulic brakes can theoretically suffer, like brakes themselves, from vapour lock. Especially if the Slave is located in a "hot spot". Outside chance but maybe worth considering?. Fluids should be replaced periodically anyway. In my view, even silicone`s?.

Pete

[iainjames]

quick update managed to get the slave cylinder off from underneath not easy but miles better than removing the dreaded Tunnel. nothing really seemed wrong with it but got a replacement anyhow. I attached a socket to the end  of the bar that actuates onto the clutch arm was a tight fir and superglued it on. Bled the clutch and it sorted it the biting point is no longer through the floor but about a third of the way on the pedal. No grating going into reverse. I am not sure how long this fix will work for and maybe the gearbox will need to come out but so far on a 20 mile drive was fine.    

[johny]

Its a pity you didnt get a picture of it Iain as it sounds like an interesting modification😁 Not sure about the use of superglue as in my experience its one of those things that can sometimes work really well and other times be a real disappointment....

[iainbja]

in truth the socket was a tight fit on the plunger thing just used superglue to steady it. I think also its always under some pressure against the clutch arm . 

 

[Colin Lindsay]

On 30/05/2022 at 10:31, iainjames said:

I attached a socket to the end  of the bar that actuates onto the clutch arm was a tight fir and superglued it on. Bled the clutch and it sorted it the biting point is no longer through the floor but about a third of the way on the pedal. 

So you extended the push rod? Not sure about the long-term capability of superglue but it's an interesting solution! (Not the glue, the extension    ) Full marks for enginuity or however you spell it.

However that means you move the piston further for less pedal travel, but is there an issue with the pedal not being able to move in the first place? Have you checked round the pedal eg for carpet getting in the way or any other kind of obstruction? The longer rod on the cylinder might be a good idea too.

[Pete Lewis]

a longer push rod just repositions the piston within the slave it might cure some gemetry or pushrod length problem but cannot have any effect on 

the clutch basic operation the thrwout and diaphragm remain exactly as was.

if you reposition the piston then as wear takes place you may cause it to slip if the piston is allowed to bottom out 

did the piston bottom out on its intended travel due to the variety of parts used ??

it all sounds like air was present 

as Colin says its very important the pedal is free to return to its stop or recouperation fails if the pedal pushrod  is holding the master just off its seat

Pete