New clutch master cylinder not filling with fluid after replacement

I installed a new master cylinder (the truck is at about 120K mi) but when I reconnected all the plumbing, it seems like it is not filling with fluid. The pedal seems two have two extreme states of being depressed and being released, meaning nothing in between, kind of like a power switch, it is on or off. When depressed, the pedal just stays in, does not go back. I did refill the brake fluid (which also feeds the clutch system) after reconnecting all the lines and hoses.

What could be the cause of this? Could there be a plug inside the cylinder fluid intake valve (kind of like it was inside the line out valve, I assume to prevent dust from coming in) that I should have taken out before installation?

 

Unfortunately, been there, done that. There is still air in the system. With brand new master cylinders, it does take a lot of pumping to purge the air out of the lines. I would recommend re-bleeding all 4 brakes and ensure the master cylinder reservoir stays full during bleeding. Even 1 bubble of air can lead to the entire system not working!

Did you pre-bleed the master cylinder prior to installation? that can shorten the install / bleeding time.

 

Do you mean this?

 

Can I pre-bleed it while it is installed if I just take the line valve out so the air can escape?

 

sorry im unable to check youtube at the moment. If it is installed already, I would not bother removing any of the lines. I would continue bleeding it using a proper method. I usually either: a.) get a pump on the clutch slave and "vacuum" out the air and brake fluid. or b.) if you dont have a evacuation pump, you can do it manually: I would give it 3-5 pumps, hold the clutch pedal down, and then open the release valve. Continue this until 0 air is coming out. But be cautious, as the air is not always a bubble, but more of an emulsified mixture of air and brake fluid (little tiny air bubbles that are barely visible). So just ensure it is 100% fluid running thru the line. Hopefully this helps.

 

i guess i just learned the word emulsified. nice !!

 

I've bled the clutch system numerous times and it has never bled in the normal manner. What I do is fill the reservoir, then open the bleeder on the slave and pump the pedal repeatedly with the bleeder open the whole time until you start getting fluid out. Then you can close the bleeder and bleed it normally as you would brakes. I also mean by pumping push the pedal down and manually pull it up repeatedly until you get fluid.