I am looking for some practical problems solving. I just rebuilt the clutch master cylinder and replaced the slave cylinder on my 72 Sprint. I have read many posts about how difficult it is to bleed the slave cylinder but I have tried several ways. When I depress the clutch pedal, it goes to the floor with virtually no resistance at all. Needless to say, the clutch does not engage.
Now I am left not knowing if my master cylinder rebuild did not work or if I just have not properly bled the system. It seems to me that I should have some resistance, e.g., mushiness from the clutch, but with no resistance at all, I am not sure which is the problem, master cylinder or slave cylinder.
If anyone has experienced this or has any thoughts about how to proceed, please let me know.
Sometimes the master cylinder piston during bleeding will hang up in the compressed position. To free up press the brake pedal by hand until you feel contact with the piston. Once there pump the pedal rapidly by hand so that the pushrod is tapping the piston. This will normally free the piston so it returns to the uncompressed position and you can then resume bleeding normally.
I built a reverse brake bleeder with a garden sprayer tank (buy the smallest one they have at the hardware store). Fill it with brake fluid, pump up some pressure (maybe 5 pumps), and attach some clear vinyl tubing (I think used 1/4" interior diameter or maybe 5/16" inch.
Then when you pull the trigger on the gun, brake fluid emerges through the clear vinyl tubing and you can watch to make sure there are no bubbles. Make sure your clutch master cylinder is empty, jack up the front of the Elan quite a bit (I have a 67 FHC with Spyder chassis), and attach the filled vinyl hose to the bleed nipple which is a bit of a bear to get at with a Spyder chassis. Open the nipple and press the trigger until the clutch master cylinder is full (it may start spilling on your face). The fluid fills from bottom to top of the clutch system, and at least for me, I had a hard working clutch pedal the first time.
I have used this method with great success also on my MGB, which has similarly difficult clutch to bleed.
Is the bleed nipple in the slave cylinder at the higest point. The sandwich plate captivates the cylinder at an angle and one hole sits higher than the other.
Is the first master cylinder you have rebuilt? There is a tricky little valve which is at the end of the master cylinder assembly in a little white plastic cup which is easy to fit incorrectly. If it is incorrect, it won’t seal, and all that will happen when you press the pedal is the fluid will go back into the reservoir.
You could look into the reservoir with a torch when an assistant presses the pedal. If the fluid level goes up, then there is a problem with the valve.
You need to look inside the brake fluid reservoir to see if there is some flow front to rear : the level is not going to change as no fluid is going to accumulate somewhere, but in case of malfunction of the return valve (at the front end of the master cylinder) the fluid will be pumped in the circuit via the pressure port(s) and return immediately via the return valve.
Here is a follow-up to my problem of whether my rebuild of the clutch master cylinder or the new slave cylinder was the culprit for having no clutch. It turns out that it was both. I replaced the master cylinder with a new one from RDent. It felt much better than the rebuilt one, more back pressure. But, still no clutch. The solution was to bleed the system using a pressure pump, lent me by Tony Vacarro, and to make sure the bleed valve on the slave cylinder was at the top. Once that was accomplished, everything worked perfectly.
However, getting there was not easy, once you put the slave cylinder into place, you can not turn it to get the bleed valve on top. You have to back it out about 3/8 of an inch so that it clears a tab on the bell housing that allows you to turn it so the bleed valve is at 12 degrees top dead center.
I would recommend that if you are replacing the slave cylinder, you bleed it first before pushing it home for its final position. I would also recommend using anti-seize on the slave cylinder body to prevent it from “becoming too attached” to the bell housing mount if you plan on rebuilding the one you have rather than buying a new one the next time it wears out.
Thank you all for your suggestions,
I think that when I am finished rebuilding my Elan, I will have done it 3 times.
you’re too kind wrote that too quickly without realizing you were on clutch, not brakes… one issue Girling clutch can’t have is the front valve failure, since they don’t have a front valve (unlike Gilling tandem MCs)…
yes, but I find it less prone to issues than the tandem brake MC as it is just sealing towards the end of the bore (better guidance for the diameter and seal width probably).
wrote that too quickly without realizing you were on clutch, not brakes… one issue Girling clutch can’t have is the front valve failure, since they don’t have a front valve (unlike Gilling tandem MCs)…