Clutch petal stays up with too much pressure car stays in neutral like pedal is pressed to floor

They will usually have a bad slave cylinder or clutch master cylinder. See if you see any leaks at those parts. The clutch master cylinder may leak on the back side so you may have to look underneath the dash to see it. Fill with fluid and pump pedal, have someone look while pushing on pedal. It will be wet from the leaking fluid.

Key cylinder

Clutch hydraulics has air in it or the clutch master cylinder is failing.

my truck starts right up if I hold the petal to the floor but wont start if I don't hold petal to floor

Your clutch fluid reservoir may need brake fluid-yes, it uses brake fluid as a hydraulic fluid. Check reservoir on the firewall. It will sit beside the brake master cylinder. The reservoir sits atop the clutch master cylinder.
If it was dry, the clutch may need bleeding down at the slave cylinder on the transmission housing-where the clutch fork sticks out of the transaxle.. Open the bleed valve on the slave cylinder, and have someone slowly press clutch down. Keep bleeding until a steady stream of fluid comes out when clutch is pressed. Then close bleed valve, check clutch operation-pedal should have some pressure on it now.

Probably bad clutch master cylinder and/or slave cylinder. I always replace both.

need to lube pedal assy under dash. other thing but less likely is air in system

It sounds as if you have 2 problems here.

The fact that the clutch pedal went to the floor and stayed there suggest a fault in the master cylinder. It may be that you need to overhaul the master cylinder.

Overhaul kits are available at less cost than a clutch master cylinder:
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The grinding noise ... A grinding noise would be caused by either the gear not engaging properly because of the defective clutch.

Or, if it is more of a squealing noise - that may be the clutch release bearing at fault.

Are you absolutely sure that your entire clutch unit - pressure plate, driven plate and release bearing aren't worn?
116results for isuzu rodeo clutch

remove the gearbox to replace the clutch.this will teach you not to hold it on hills on the clutch but to put handbrake on and neutral.also the same at traffic lights and no boy racer flying starts where accelerator is floored and clutch ridden slowly to get most power to wheels,still its not difficult to change and clutches not that expensive if you do it yourself,garage price around 800 euros

Under the dash look to see if there is a spring attached to the petal or maybe under the hood. Or you might have something getting in the was of the petal arm. Good Luck and PEACE