420 or 3.8S Clutch Master Cylinder Help

I have a 1967 420 with manual transmission, I’m having problems with the clutch master cylinder not releasing completely. It’s all new or rebuilt. I’m afraid I’ve shortened the life of my bearing, but need to get this right. I’ve adjusted the clutch 3 times and it pumps up and holds enough pressure as to not get returned by the spring. If I loosen the line or bleed screw it backs off. When it does I have lots of excess end play until I pump the clutch again.

Problem is the original type master is not available. The one moss lists Mk1,2, 420 has the can clocked wrong so won’t fit my car. I found a master for a Saab 9000 that would fit with a remote can, but seems to be unavailable. Wonder what others have done??

Just looked at SNGBarratt, a new master brake cylinder is available ( but in backorder now ).
A 3.8S-type is the same as a mk2, it will not fit.

I’m talking about clutch master cylinder.

Hi, I know what you mean as I just replaced the master clutch cylinder in my 420. There are NONE available. BUT, the master cylinder for a MK2 can be made to fit. You will have to reroute the heater hose and use a longer elbow hose. First, disconnect the top heater hose then get a longer heater hose from an E type and fit it. It will be a tight squeeze. You MUST also change the push rod as the 420 is longer than the MK2. Just take it out swap new seals and reinsert into the new master cylinder. Works like a charm. The new master from SNG is not a Chinese knock off, but a beautifully made UK Lockheed cylinder.

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Don’t know that this will help, but the Rover 2000 clutch master cylinder was fitted to the last of the Stypes, and was the only replacement cylinder available from the 1970s onwards.

Send a picture
I have old crap laying around
If not Dave does
We are talking master not clutch slave?
What is the bore and all

Yes Clutch master cylinder.

Oy Vey…call Dave Welsh at Welsh he might have that um uh…unique piece :slight_smile: gtjoey1314

Thanks! I’m going to try a rebuild kit that has the later "improved " piston with ring seals.

You might get White Post or Apple Hydraulics to sleeve your existing cylinder and with a rebuilt kit, assuming they are available, yours would be better than new.

My current one was new old stock with new seals a few months ago.

If I understand your symptoms correctly, you could have a blocked flex line, On my 3.8S this is a short rubber hose from the bulkhead to the back of the cylinder head, They can deteriorate internally and act as a one way valve.

I would hope not, but just because something is new doesn’t mean it’s any good.

Well thought I’d give an update. I put a seal kit in my new old stock master cylinder. Installed an adjustable push rod in it. I installed the master cylinder and set the rod so the clutch pedal is even with the brake pedal.

I adjusted the slave push rod per the service manual. Bled the master cylinder and could not get enough travel to operate the clutch. I noticed the spring would return the slave so far the master can’t make up the travel. Then I removed the spring and the clutch operates well. I put a link on the push rod pin at the slave cylinder so the spring can’t pull so far. The clutch operates fine, but the pedal operates at the very end of the travel. The throw out bearing just barely makes Contact or is slightly off the pressure plate.

So I know my previous master cylinder push rod was modified longer and was too long. Now with the adjustable type, should I lengthen the slave end or pedal end or just leave it?

After my last post I noticed in the 420 parts and shop manuals I have, the spring is not installed. I will remove the spring in the morning and I bet the clutch will feel better. SNG and others listed 420 in the application for the spring and tab.

Your on the right track
Since you don’t know the condition of your throw out bearing , come close and bleed the master over and over
Adjust the rod a hair tighter and see if that gets you close
Drive it with the clutch not just static testing
Good luck

Removal of the spring makes it operate perfectly.
I have a new clutch with nos bearing in it. I have been driving it each time. I did put the spring in, but so loose it doesn’t do much at rest.
Thanks again for the help.

Keep in mind when Jaguar went front spring type clutches to diaphragm type around 1965 the cars got a new slave cylinder, This is what I call the “long” slave cylinder versus a shorter one used previously. All 420 cars (as well as 4.2 E Types) should have the diaphragm clutch and the long slave which, according to the work shop manual and the TSB launching the diaphragm clutch is intended to operate with out a return spring. This system is known as the hydrostatic hydraulic clutch. Recently, when my spring clutch 1965 3.8S got a engine overhaul and upgrade to a diaphragm clutch and long slave the shop did fit a return spring. It seems to be working fine so far. Running without a spring causes me some worry as it seems it COULD cause early throwout bearing wear. The earlier system was very specific in setting a small amount of clearance to prevent this using the adjustment provided at the pushrod connection to the clutch fork… Hydrostatic clutches were launched to build in an automatic adjustment feature. There is much discussion on this topic on the E Type forum. What is really needed is a slotted hole in the slave cylinder operating rod where the clevis pin fits at the clutch fork end and a spring that would only take up the small distance (slack) achieved by the slotted hole, not the slave’s full travel.
Comments welcome.

I figured that last night. I have the diaphragm clutch. I too worry about early clutch bearing wear, but MGBs do it the same way and don’t suffer from wear. I keep my foot off the clutch as much as possible.

I once made the mistake of adding a return spring to a 69 e-type. Bad idea. Not intended to be used and results in the retraction of the piston in the slave, need for increased travel of the clutch master to the point that the clutch could not disengage. Took me a long time to figure that one out! My '68 E is the same way and I’ve run it for 20+ years without a spring. I don’t think you will see a problem.