I have a friend with a 98 chevy k-2500 with a 350cid 5sp. 4wheel drive. He is having problems with the clutch pedal. I know he is losing fluid. What is the best guess on the culprit. I haven't seen the truck yet and wondered if anyone had known of any problems? I'm thinking of clutch master cylinder, where is it located on this truck? anyone with some help, I would greatly appreciate it.
Thank you!!

I would check the line between the cylinders, usually a culprit the way it snakes around the tranny,
The master cylinder is located on the firewall on the drivers side by the brake booster,
Fullsizechevy.com is a great resource for those trucks

thank you for your help