Hey guys, got a 93 honda accord coupe and I just replaced both the master cylinder and slave cylinder for the clutch. Iv bled the line multiple times now, but after doing so I will have absolutely great pressure on the pedal, but over the course of 10-15 miles, the pedal will just slowly start to loose pressure until it is almost lying down on the floor. Then if I go into a pumping frenzy, it will come back up.
I figured air in the line a couple of times now, and sure enough, I will usually get a froth of air bubble laced fluid to come out of the slave cylinder, but I have gone through an entire LARGE sized jug of brake fluid. And I even went of my way to make sure that not only was all the air out, but the fluid was as clean and clear of micro air bubbles as possible. Topped it off, same problem. Pedal feels great at first, eating the floor pan 15 miles later.

Here is the weird part, no leaks.....I have no wet spots in the drive way where I park it or on the rod under the dash. I have not lost any fluid out of the reservoir, and nothing on the inside of the cabin....Iv replaced everything but the line, its my next go to, but was curious if anyone else had this issue or could point something out to me if replacing the line is more of a hassle or something to help here.

 

Its strange for the fluid to disappear without a trace...

Leaking at the master-cylinder shaft seal, it usually soaks into the padding beneath the carpeting without becoming visible at the push-rod. Have you checked there?

 

Nope. I replaced my clutch master cylinder in my 97 (also the slave) because I had fluid coming out of the back of it into the car like Jim described. But, it bled down just fine and I had no issues with it. It did take me a couple of attempts to adjust the push rod, so it wouldn't slip in gear though.

 

well that's the weird thing, its not leaking. I getting air in the line and loosing pressure in the pedal. Im not loosing fluid.