air in clutch system

Thanks all
I think the idea to look for even a glimmer of leaking fluid may be of help. Ive been looking at it like brake hydrolics with higher pressure and noticable leaks. The bleeder screw might have a glimmer of leak and through the pumping allows more air in than fluid out. I'm sure I now have it tightened to the point it will twist off in my wrench with a little more force (I really hate when that happens) so I will hunt down a new bleeder and try that. I believe the rebuid good although posiblely unnecesary even after 44 years. It works perfect after I bleed it and will even work perfect after I bleed it and it sits. Only when I use it does it get air in it. Pumping it does overcome the air but going from 1st to nuetral with no clutch then franticly pumping 8-9 times stopping (non-syncro 1st ) and slipping it back to first in traffic is rough on the nerves. I'm about the age of the car and in the not to distant future might even understand the "trailer queen" love of Jags.
Thank you all again
Vin

Sorry Vin, I sometimes don't read as closely as I should. Assuming your rebuild is good; the walls of the cylinders not pitted; and rubber lines replaced, there's really not much to do.
I think I would re-bleed the slave cylinder again.

Patrick

Vin,

Are you sure it is air in the system? I'm not familiar with the lines in the Ser. I cars, but I know in the Ser. II cars there is a rubber hose that goes around the top of the transmission behind the engine, between two sections of hydraulic tubing. Over time, the inside of that hose goes bad and can delaminate, causing a blockage in the hose which can affect the clutch performance. Also, the tubes themselves can corrode on the inside if moisture has built up (many people bleed their brakes every couple of years, but go decades without changing the clutch fluid, which is just brake fluid).

If you have already rebuilt the master and slave cylinders, I'd seriously consider changing that hose (if you car has one) and the metal tubing. It's not a major job and that way you know the system is in good condition.

Hope that helps,
Steve

Hi Vin

Not only do you need new rubber parts, as Patrick points out, but the bores of both master and slave cylinders must be smooth and without pits. Usally old bores are pitted because the brake fluid absorbs water which it turn rusts the steel cylinders. Most old cylinders need to be sleeved in brass or stainless. This is better than a new cylinder because the sleeve will not corrode significantly.

Any leak in the system will let air in. You must be sure there is no fluid leak at any joint. Press the pedal down hard for a few minutes and look for any glimmer of fluid at each joint.

For proper bleeding the bleed nipple in the slave cylinder must be at the highest point on the cylinder I find I have to remove the slave cylinder and hold it together while my wife slowly pushes down the pedal.

What happens when you pump the clutch pedal? That should overcome a bit of air in the system.

Good luck

Curt

Edited on 2008-07-21 7:22:32

Edited on 2008-07-21 7:21:50

Just a shot in the dark here, but if the internal parts are still original, then its time for a rebuild. Spare tires rarely last for 44 years, much less the rubber inside hydraulic cylinders.

It is my understanding that air in a hydraulic system produces a spongy pedal. But in your case, it sounds more like the hydraulic fluid is just blowing back behind the cup that is doing the compressing. Another test would be just holding the clutch down under pressure to see if it holds (similar to brakes). If the pressure does not hold, then the clutch will slowly engage...I don't know that you will feel this through the pedal though. (If it were brakes, then the pedal would slowly fade down to the floorboard.) Did you by any chance switch from DOT 3/4 to DOT 5 silicone? If so, you may have ruined some of the internal parts.

But if you are still running on 44 year old internal hydraulic clutch parts, I would be VERY afraid of your brakes too!! Personally, I would have the master cylinders (all) and brake calipers lined with brass or stainless steel.

Just a hunch.