I have a 1999 Kia Mentor manual transmission, I was driving and lost pressure in my clutch, can some one help me.

There are 3 progressively difficult and expensive steps you can take. I have to assume that the Mentor is the same as a Sephia.
First: Check the level of fluid in your brake/clutch canister. It MIGHT have 2 separate canisters (like the 1995 Sephia.) But I doubt it.
Second: Check your hydraulic clutch cable and the unit at the transaxle. It may need to be bled.
Third (and most expensive): Replace your clutch and pressure plate. This is the most expensive as it requires removal of the engine.

I hope this helps you find the source of your difficulties.

You don't state mileage on the car but I'm betting well over 100K. The master cylinder is sold as a one piece kit which has the line and the slave cylinder attached to it. More than likely your slave cylinder has gone bad, which means you'll have to drop the transmission to get it out as it's an internal mechanism that pushes your throw out bearing to engage your clutch. Yes it's time to also change the clutch and pressure plate too, you may as well as long as you have to drop the transmission AND in order to do that my friend, you're going to have fun, because the whole front of the car has to be lifted and the WHOLE X sub-frame has to be dropped which means struts and all have to be disconnected. NOT a fun driveway weekend job unless your young, don't mind bending and kneeling on concrete and have power tools, air guns, to make it easier. Strong arms if you're going to attempt it with hand tools. Good luck to you.

FIRST YOU MUST MAKE SURE THAT YOUR CLUTCH CYLINDER IS PUSHING YOUR PRESSURE PLATE ON THE TRANSMISSION... OR IT WILL SEEM LIKE YOUR CLUTCH IS WORN OUT WHEN ITS NOT. THEN REMOVE THE TRANSMISSION AND REPLACE THE CLUTCH.. YOU WILL NEED THE PLASTIC CLUTCH INSTALLATION GUIDE TO SET THE CLUTCH AND HAVE IT HOLD IN PLACE AS YOU PUT THE TRANSMISSION IN... IF YOU DONT HAVE A SECOND PERSON TO HELP YOU.. IT IS SAFER TO PAY A MECHANIC TO DO THE WORK VERSUS YOU GETTING HURT.. SOME MECHANICS JUST CHARGE 150 TO REPLACE AND CLUTCH COST THE SAME OR LESS. FOR MORE INSTRUCTIONS FOR YOUR MAKE AND MODEL WITH PICTURES GO TO BESTDIRECTORYSOLUTIONS.COM

It sounds like a bad clutch. It is the clutch if you can change gears with the clutch out and the engine running.

The clutch pressure plate might be weak in the manual transmission.

I wouldn't worry if it doesn't cause a problem in changing gears, until you have the clutch changed, if you ever get that far.

low brake fluid level. top off and see if that does it

how to remove gearbox from a '97 kia mentor. How do you remove drive shaft connected to gearbox. Does anyone have a manual.

1 Inspect Clutch Disc Contaminated Clutch or Pressure Plate Surface. 2 Inspect Clutch Disc Worn or Damaged Clutch Pressure Plate. 3 Inspect Clutch Disc Improperly Adjusted Clutch Cable or Linkage. 4 Inspect Transmission Shift Linkage (Manual) Loose or Worn Shifting Linkage. 5 Inspect Clutch Disc Broken, Missing or Weak Clutch Disc Springs. 6 Inspect Clu 1 Inspect Transmission Modulator(Automatic) Modulator Leaking Fluid into Vacuum System. 2 Inspect Transmission(Capacity) Fluid Level Incorrect. 3 Inspect Transmission Fluid Type Contaminated Transmission Fluid. 4 Inspect Transmission Filter (A/T) Clogged or Dirty Transmission Filter. 5 Inspect Automatic Transmission Internal Transmission Problems.tch Disc Broken, Missing or Worn Pressure Plate Diaphragm Fingers.

Try adding a bottle of Lucas Heavy Duty Oil Stabiliser to the gearbox, it made hell of a difference to my Kia

First thing to check is the transmission fluid, if the problem does not go replacing the fluid, then on a manual transmission you need to replace the transmission.
On an automatic transmission can be a problem with the control module or with a defective sensor.