master or slave clutch cylinder?

[cbguerrajr]

Looking for tips from our experts, to possibly save some work. I have a failing clutch hydraulic system in my Elan, and would like to undertake the more likely repair first. I can't tell what is more likely the culprit: the Master or the Slave cylinder. (both jobs are equally nasty to do),
here are my observations:

* the hydraulic parts (SC, MC, lines) were new 7 years ago.
* about a year ago, all clutch mechanical parts (inside the bellhousing) were replaced coinciding with an engine rebuild and everything worked great for awhile.
* at that time, I added tubular exhaust headers. then gradually, the clutch pedal started acting up. I assumed that the heat from the exhaust, directly under the slave cylinder may have damaged the seals, or had caused a gas bubble to develop in the system.
* The pedal had to be pumped to disengage the clutch at the right point in the travel. After inactivity for less than a minute, the pedal would almost go to the floor again and had to be pumped, or gears could not be engaged.
* Bleeding the system several times did not help.
* There are NO hydraulic fluid leaks.
* While bleeding the system a couple of weeks ago, things appeared normal, there was good fluid flow coming out of the bleeding hose and no air bubbles. But pedal action did not improve.
* So yesterday I tried bleeding the #$@*% system again. This time I noticed something new and different. While working the clutch pedal, I saw the fluid level in the MC reservoir going up and down with each stroke, but with little or no fluid coming out of the bleeding hose. Needless to say, this didn't help, and the car now is not drivable at all.
* I have obtained a SC rebuild kit, but now I wonder if the MC could be the problem instead.

Any insight or advice on this? I would be greatly appreciate it. thanks.

Carlos G.
1966 S2

[StressCraxx]

It could be the hose has collapsed internally. Try replacing the hose. The other possibility is the check valve in the master.

[cbguerrajr]

"the check valve in the master" sounds like it could explain what I saw. That means replacing the master?
(I doubt that the check valve itself could be replaced...??)

[Andy8421]

Carlos,

There is a small rubber seal at the end of the piston assembly that seals off a port to the reservoir as soon as you depress the pedal. If the fluid level is going up in the reservoir when you press the pedal, then this seal isn't doing its job. Instead of the fluid being forced along the pipe to the slave cylinder, its just squirting back into the reservoir.
This wouldn't explain all your symptoms, so you may have other problems as well, but I can't think of another fault that would result in the fluid level going up in the reservoir when you press the pedal.

- Carlos I just saw your reply. A master cylinder rebuild kit has all the seals and bits to replace this part.

[Chancer]

No fluid leaks = master cylinder problem.

[nigelrbfurness]

+1 for the master cylinder, but replace the whole lot including the flexible hose otherwise problems will return quickly. And you only have to fill and bleed it once!

[alan.barker]

If you fit a new master cylinder which is the best way check that the length of the piston rods are the same. You may need to use the old piston rod in the new master cylinder
Alan

[rgh0]

Personally I would rebuild the master cylinder rather than replace. If the master cylinder bore has excessive wear I would sleeve the master cylinder with a stainless steel sleeve as that will last longer than a new master cylinder.

cheers
Rohan

[Bigbaldybloke]

Just warning note, there was more than one size of master cylinder, if replacing make sure you get the same size or you can find the clutch is very heavy if you fit a larger one. Same if ordering an overhaul kit, make sure you get the right size. As far as I know there is no way to tell what size you have from the outside, you have to strip it and measure the cylinder bore, unless others know different? The manual tells you what should be in there, but unless you have had the car from new you can never be sure as somebody else could have changed it at some stage.

[alan.barker]

You can tell before stripping there should be next to "Girling 5/8" "
If you order a new one be sure to ask for 5/8" dia. Many classic cars had these.
Imho i would fit new master cylinder and order from same supplier also a repair kit (very cheap).
Alan

[cbguerrajr]

guys, thank you for all the good advice and tips. MC was already ordered, so have I
to make sure it's the right size, etc.

Carlos

[patrics]

Hello Carlos,
You don?t say if it is an original make master cylinder or something else
What fluid do you have in it? ? I?m assuming not silicone

So Based on your comment
?yesterday I tried bleeding the #$@*% system again. This time I noticed something new and different. While working the clutch pedal, I saw the fluid level in the MC reservoir going up and down with each stroke?
You should hydraulically blank off the master cylinder and check if the pedal is solid ? if not strip it down and check for debris around the front seal ? clean and rebuild and check if pedal is now solid ? after bleeding of course.
If not change the master cylinder.

Okay assuming all is okay with master cylinder then you have air in the system.

Regards
Steve

[crannyr]

After 7 years, sleeve and rebuild both.

[billwill]

You should hydraulically blank off the master cylinder and check if the pedal is solid ? if not strip it down and check for debris around the front seal ? clean and rebuild and check if pedal is now solid ? after bleeding of course.

Steve

I don't think you can do that with an Elan master cylinder as the reservoir is an integral part of the master cylinder.

[alan.barker]

To blank off just put a flexible hose clamp on the flexible hose in the line. If the line is still as original and not with an Aero?quipe type hose.
Imho the problem for bleeding the clutch circuit is the slave cylinder. The bleed nipple on the slave cylinder can not be positioned at the highest point. There is a flat and also the metal sandwich plate which blocks the orientation.
Some people bleed the clutch circuit complet before the slave cylinder is mounted in the bellhousing lug. To do that they use a homemade clamp to stop the slave cylinder piston popping out during the bleeding.
Alan