Clutch servo

Moderators: Aceman, ecosselynx

4jagsjohn
Posts: 55
Joined: Mon Jan 16, 2012 10:49 am

Clutch servo

Postby 4jagsjohn » Sat Dec 15, 2018 2:44 pm

Hi everyone. I have finished me ground up rebuild of my Mk2. I want to fit a clutch servo to reduce the load on the old leg. (My trusty E type is auto ) I was going to change the Mk2 to auto but entailed to greater amount of work. As I wish to use this car a lot in the future can anyone advise as to where to locate the servo as very little room in engine compartment as you will know. I have fitted power steering so no room as such on the exhaust side. I daresay under a wheel arch is a thought but not good for weather intrusion. Any advice would be much appreciated. John

340jag
Posts: 116
Joined: Sat Apr 22, 2017 7:35 pm

Re: Clutch servo

Postby 340jag » Mon Dec 17, 2018 9:36 am

You could put the battery in the boot , free up some space !

4jagsjohn
Posts: 55
Joined: Mon Jan 16, 2012 10:49 am

Re: Clutch servo

Postby 4jagsjohn » Mon Dec 17, 2018 11:26 pm

Good point. I nearly did when I did my rebuild but changed my mind. If can't think of anything else may well go down that road. Cheers.

Martec
Posts: 961
Joined: Tue Apr 07, 2009 7:08 pm
Location: North Lincs

Re: Clutch servo

Postby Martec » Fri Jan 25, 2019 9:10 pm

Hi,
I fitted a servo for the clutch under the front wing, waxed it and put a cover over the air valve, it has served me well for quite a few years,
I used the small servo that is sold for mini's.

Brian
MY2000 3ltr S type manual standard car with leather seats, cruise control and mistral blue metallic paint.

1961 3.8 MkII manual, Indigo blue, nolonger runs on LPG, everything else uprated

4jagsjohn
Posts: 55
Joined: Mon Jan 16, 2012 10:49 am

Re: Clutch servo

Postby 4jagsjohn » Sun Jan 27, 2019 11:30 pm

Thanks your reply Brian. I will go down that route as it is the best option I think.

B87UL
Posts: 15
Joined: Fri Sep 18, 2015 7:32 pm
Location: CAMBRIDGESHIRE

Re: Clutch servo

Postby B87UL » Mon Jan 28, 2019 12:21 pm

John
I was going to fit a clutch servo and worked out, as Brian has done, that taking everything into consideration the best location would be under the right front wing. My intension was to fit a remote breather by utilising an old type Briggs Strattan lawn mower crankcase breather. In fact I actually purchased a small servo but so far it is still on the workshop shelf.
Instead I decided to fit a larger bore clutch master cylinder from SNG Barratt. I have fitted a temporary back stop arrangement on the slave cylinder to allow positive clutch bearing clearance, this stop also allows me to adjust the clutch pedal take up position to my personal liking. This has improved the situation and is satisfactory for me at the moment.
I would be interested if Brian could say if he can obtain a satisfactory clutch take up position near the bottom end of the clutch pedal position. If you do have issues with a heavy clutch operation I find the actual take up position can make all the difference.
Should you do go down the route of fitting the battery in the boot it is worthwhile considering coupling up in the boot via an Anderson plug and socket. I have a 1965 S type with batteries in both locations, original and the boot, but I would not fit one in the boot unless I absolutely had to do so.

4jagsjohn
Posts: 55
Joined: Mon Jan 16, 2012 10:49 am

Re: Clutch servo

Postby 4jagsjohn » Thu Mar 14, 2019 4:36 pm

Sorry my late reply thanks your advise. I shall probably go with the mini servo option shortly. Putting up with heavy clutch at present. Did the larger bore slave you fitted make the clutch pedal lighter by a good amount. Thanks for your advise. John.

B87UL
Posts: 15
Joined: Fri Sep 18, 2015 7:32 pm
Location: CAMBRIDGESHIRE

Re: Clutch servo

Postby B87UL » Thu Mar 14, 2019 8:32 pm

John

I used a larger master cylinder, not a larger slave cylinder. I found it improved matters so that the clutch effort was acceptable for me. You need to be aware that a larger master cylinder displaces more fluid on each stroke and the clutch pick up point will alter. However you might well find that situation occurs with a servo in any event.

Having said that, I found the original clutch pick up point was not acceptable to me and needed a back stop fitting to the slave cylinder and the fitting of the larger bore master cylinder. Now the slave cylinder allows adjustment so that I can set the clutch to pick up just as I ease my foot from the floor. Although I am past my four score years and ten, I have driven the car on fairly long trips to Eire and France, with no problem to me.
Norman

Martec
Posts: 961
Joined: Tue Apr 07, 2009 7:08 pm
Location: North Lincs

Re: Clutch servo

Postby Martec » Sun Mar 17, 2019 3:21 pm

Hi,

I've just replaced the clutch fluid and started it up, the clutch bite it close to the top of the peddle.

I moved the battery from the front to the boot on another car and found there was a big volt drop even with a heavy cable front to back, so I fitted a very large battery and ran a separate cable for the radio that kept losing its tuning. What I should have done was to run another big cable to feed the new high torque starter.

Brian
MY2000 3ltr S type manual standard car with leather seats, cruise control and mistral blue metallic paint.

1961 3.8 MkII manual, Indigo blue, nolonger runs on LPG, everything else uprated

B87UL
Posts: 15
Joined: Fri Sep 18, 2015 7:32 pm
Location: CAMBRIDGESHIRE

Re: Clutch servo

Postby B87UL » Mon Mar 18, 2019 12:31 pm

Brian
Is that the first time you have experienced the clutch bite at the top of the pedal stroke, or was it like that before you carried out a recent fluid change?

Further, are you looking to change the bite point, or are you accepting that situation?

Some years ago, as a young automotive engineer, I had to cure a clutch throw out problem on a large number of trucks. They had a similar, if not identical layout, to the Jaguar with hydrostatic cylinders. In the early to mid-60’s a number of manufacturers tried, and then had to modify the clutch hydraulic system, looking at the number of their cylinder changes, Jaguar were no exception.

On both truck and car we experienced slave cylinders being pushed back under motorway driving conditions, so that there was no clutch action on the first pedal stroke. The other, not so common, problem was “hydraulic compounding”, and I can see the possibilities with the Jaguar. This normally occurred when the driver could not select 1st or Reverse; they would then operate the clutch pedal two or three times. At that point the clutch would over stroke if the pedal had been pumped fast, the action really replicating the movement and self-adjustment of disc pads. Sometimes the compounding would cause breakages to the clutch forks or front gearbox front plates.

Basically I ran a fleet campaign to convert them all with cylinder return springs and a cylinder back stop arrangement. This had a number of advantageous; it allowed the cylinder to withdraw sufficiently, it provided a method of setting the clutch pedal bite position, and it prevented clutch over stroking in practice.

It seems to me that you have not come up against any of these problems even with a clutch servo fitted, with the exception that the clutch pedal bite position is high. Am I correct with this statement?

I am particularly interested because years ago I cannot remember modifying any Jaguar’s, probably because they were usually Automatics, I have obviously modified my own S Type, but am interested in other owner's experiences, particularly with a servo.

As an aside, I see you have a 3.8 ltr equipped for LPG, interesting in 1979 I had some 60 cars running on Propane with our own bulk tanks, about 10 of those were 4.2 Daimlers. Just don't try fitting LPG to 1970 / 1980 ish Cortinas

Correction….. my four score years, should read three score years

Martec
Posts: 961
Joined: Tue Apr 07, 2009 7:08 pm
Location: North Lincs

Re: Clutch servo

Postby Martec » Mon Mar 18, 2019 5:47 pm

Hi,
I have 4 score years and 11!!??
The car was run on LPG but an old LP suction system infront of the carbs, but the repairs cost more than the fuel cost savings, much nicer to drive now back on petrol.

I believe the bite point has always been near the top and have no wish to adjust it. When I rebuilt the car and engine I replaced the short slave cylinder with the only one available, the later long one. I also fitted the spring from the short one and had difficulty in clearing the clutch and crunching gears. I was advised to take the spring off and it has been fine since.

I spent 32 years fixing up clapped out boats/ships!

Brian
MY2000 3ltr S type manual standard car with leather seats, cruise control and mistral blue metallic paint.

1961 3.8 MkII manual, Indigo blue, nolonger runs on LPG, everything else uprated

Martec
Posts: 961
Joined: Tue Apr 07, 2009 7:08 pm
Location: North Lincs

Re: Clutch servo

Postby Martec » Thu Mar 21, 2019 7:00 pm

Hi,
I thought I would give you an update on some knowledge I just gained from Ken Jenkins regarding my own clutch, it may help others.

I rebuilt my car from a seized rotten original wreck, it had an original 3.8 with moss box and 10" coil sprung clutch with the short clutch slave cylinder.
I returned the car to the road in 2000, but soon replaced the knackered moss box with the later full synchromesh and overdrive box, I had a new 10" coil clutch and the later long slave cylinder as it was the only one made at the time.
The other day after a few nagging doubts I jacked the car up again and checked the distance between the fork lever and pushrod with the pin removed, what should have been 3/4" was now 1 1/4", so I reset this to the correct 3/4". With the clutch peddle fully depressed the clutch fork lever is still clear of the back of the bell-housing slot, and the bite point is still near the top.

I spoke to Ken just now who was also concerned that the gap had increased (wear to the graphite release bearing) rather than a reduction in the gap (indicating clutch plate wear).

He said that although DOT4 fluid was OK for Brakes, Dot 3 was better for the clutch hydraulics as it lubricated better, also the clutch flexible pipe should be replaced every 5 years as it may be de-laminating and stopping the clutch from unloading fully.

Also that with the spring clutch I should revert to the short slave cylinder and external spring (if I can find it?) as the later long slave cylinder is really for the diaphragm (9 1/2") clutch.

So as I have always regretted ignoring Ken's advice I need to replace the flexy hose, DOT4 and the slave cylinder. That will hopefully give me another 50,000 miles over 19 years and remove the necessity of engine out to replace the clutch. Also the cost of an electric cable hoist to replace my very heavy chain blocks.

This I hope can help someone else.
Brian
MY2000 3ltr S type manual standard car with leather seats, cruise control and mistral blue metallic paint.

1961 3.8 MkII manual, Indigo blue, nolonger runs on LPG, everything else uprated


Who is online

Users browsing this forum: No registered users and 1 guest