Clutch bleeding.

[roddymacp]

I wonder if anyone can help me. Today, I have put a repair kit into the clutch slave cylinder. (Spitfire 1500) I had been only having an effective clutch right at the bottom of the pedal, with a lot of loose play in the top two thirds of travel. Bleeding it single handed is not easy, but I have a tube that is supposed to stop air re-entering on the upstroke so have been trying myself. I have now got a jam jar almost full of fluid and well above the magic split in the tube. Fill the reservoir, 6 or 7 pumps, tighten everything up, and I have a full pedal. with everything tight and the reservoir refilled I only get about half a dozen pumps before I am back to square one with most of the pedal travel doing nothing. I have tried several times to release the nipple, press the pedal, tighten nipple release pedal, and repeat, but the end product is the same. Have I done something wrong, am I doing something wrong, or could the problem be in the master cylinder? The slave area was very wet with fluid when I took it all apart, and any drips have been from this area rather than the side where the master is located. Pipe looks in good order as well.

[mikeyb]

is the slave area still wet with fluid after rebuild and bleeding?

if so what was the bore like before you replaced the seals?

did you fit the correct seals the correct way round?

[roddymacp]

Slave cylinder is not wet now. Bore of slave looked good and felt good with little finger. Seals correct way round and supplied by Rimmers.
I am just off to Halfords for a pressure bleeding kit, as I feel it might get rid of the chance of either leaving or sucking air back in. Bigger reservoir too which should help.

[willcolumbine]

Is the bleed nipple in the top or bottom hole in the slave cylinder. If it's in the bottom there is a chance air will be trapped in the top part of the slave cylinder. Also check the hole in the top of the pedal. They get elongated with time and are well worth checking.

This is a good tip too!

http://www.youtube.com/watch?v=uj1dMdYgRK4

[roddymacp]

Bleed nipple is in the top hole. Will have another go soon with the pressure kit. That is a good tip on the link. It's too many years since I ever bled brakes, but the guy in the motor shop said he remembers clutches being the very devil as air pockets gather that are too big for a single stroke of the pedal to shift.

[roddymacp]

The pressure system seems to have worked. After joining it all up, I ran nearly half a litre through the cylinders and now have a full pedalwhich seems to be holding up. I'm doing no more tonight, so will check it tomorrow and try the clutch with the engine running. If it's OK, it will certainly be a case of an unmovable airlock by pedal pressure alone.
Thanks for the addvice and moral support guys.

[thescrapman]

I was always told to do master and slave simultanoeusly as one will always fail just after you fix the other.

I think you have a deterirated seal on the end of the spring in the master.

Or the pivot pin has dropped out.

Cheers

Colin

[roddymacp]

I'm sure the scrapman is right. It's such a devil to get to the slave for bleeding that it makes sense to do the master at the same time. Have been thinking of this all day as I could have the kit on Saturday and do the job properly. Have also been wodering about cutting a panel in the gearbox tunnel so that the system could be bled without the rigmarole of stripping everything out.

[Nilfisken]

Hi, hearing about all the issues of clutch bleeding (and knowing I'm gonna have to do that soon myself ) I remember seeing somewhere on the net a suggestion of instead of using a normal circuit, construct a piece of hydraulic piping (same kind of pipe as the normal MC to slave pipe) from the place where the bleed nipple is normally positioned, route that one out to the engine bay and end in a fitting suitable for the bleed nipple. In that way you should be able to bleed the clutch as easy as you bleed the brakes straight from the engine bay which is much much easier to reach than the slave cylinder itself, right? Do you think that would work?
Cheers!

[junkuser]

Why is it that bleeding the clutch hydraulics causes so much of a problem on various Spitfire models?
On the Spit 4 I have only ever just opened the bleed nipple for a while and gravity has done the job.
Do other models have a different layouts that prevent this ?

[Brit car fan]

I had the same problem - just could not achieve a firm clutch pedal. Eventually a work mate who was an ex-motor mechanic put me right.
On the Spitfire 1500 the slave lies horizontally, parrallel with the engine - but the engine does not sit level within the car, being inclined toward the front, hence the front end of the slave cylinder is higher than the bleed nipple, so a bubble always goes to the front, away from the bleed nipple so cannot be bled out under nornal conditions.
The answer is this - Fit the slave cylinder and connect the pipe in the normal way. With the pipe still connected unbolt and carefully remove the slave. Gengtly point it earthwards by about 30 degrees (slightly bending the pipe) so that the bubble goes to the bleed nipple. bleed in this position and re-fit the slave. Worked for me first time.
Another alternative may be to jack the car up really high at the back to give a simillar but lesser effect.

[nang]

I've just replaced the clutch in my Mk4. All the pivot points were badly worn, from the master cyl. clevis, hole in the pedal arm, through to the hinge assy in the bell housing and the slave cyl pushrod pivot. This creates a lot of lost travel. Have rebushed everything and now appear to have a decent pedal, at least I can get it into gear now and clutch engages with a much higher pedal. Will be really sure hopefully tomorrow when I get everything else in and tightened up and the seat back in. I have also made up a remote bleeder. The block with the bleeder screw is all that I had with the correct fittings hence the blanking plugs.
Tony.

[Brit car fan]

Having had similar difficulties bleeding the clutch on my Spitfire 1500 I designed and made a dedicated remote clutch bleeder which was very successful. I now sell these on eBay if anyone's interested - https://www.ebay.co.uk/itm/273761793912

I've also made access ports in the transmission tunnel. The left hand one was to get at the bleed nipple on the slave, no longer needed. The right hand one exposes the oil filler hole in the side of the gearbox. The plates hook under a bracket at one end and are located with two M6 cap head screws at the other end. Both plates and the tunnel edges are lined with neoprene foam tape to seal gas tight.

Hopfully these links will work:

Driver's side: 

View on pedals:- http://oi63.tinypic.com/nl62x1.jpg

RH panel off:- http://oi64.tinypic.com/2yjsrus.jpg

RH Panel Close up:- http://oi63.tinypic.com/zmcxz8.jpg

Passenger side:

Cover Half Off:- http://oi63.tinypic.com/24nqo12.jpg

Showing Slave Cylinder:- http://oi63.tinypic.com/2u8jmn6.jpg

On clutch bleeding: Pressure bleeding at around 10psi is good. I use a Draper pump type pressure bleeder. I would not recommend vacuum bleeding as the seals are only meant to seal against pressure, under a vacuum air is bound to be drawn in. Note also my previous comment on jacking up the rear end of the car.

Dave.