I have a 1989 z24 cavilier and i just changed the slave cylinder and now when i start it and press the clutch it makes a grinding noise. When i try to put in gear it wont go in any gears and makes some grinding noises

How old is this vehicle? What mileage is on the vehicle? do you get the noise in all the gears?
If this is a grinding/crunching noise it is most likely a worn clutch. The reason it makes no noise when the engine is off is that the gears inside are not spinning. The noise is caused by the spinning gears hitting each other and missing the teeth slots on the gears.
If it is a worn clutch the whole clutch assembly will need replacing. A replacement kit is usually the friction plate, Clutch cover (spring) and the slave cylinder.

So you installed a new transmission and a whole new clutch kit? Did the kit include the pressure plate, clutch, throw out bearing and slave cylinder? Did you bleed the slave cylinder? The low and soft pedal is a clear sign that there is air in the hydraulic system. The loud noise after that tells me you're either grinding the gear trying to shift or there is a problem inside the transmission itself. If you installed everything correctly and torqued all the bolts correctly in the clutch assembly and transmission, then try bleeding the slave cylinder again, sometimes air gets trapped in the cylinder and it's hard to get out, If you let the clutch master cylinder run dry while you either had the clutch apart or while you were bleeding the clutch, then you have to start from scratch and re-bleed the whole system.

Umm...

A mechanical 'breaking noise' doesn't sound good. It's hard to diagnose a problem online without being there to see/hear the vehicle. But .. it may be that your clutch pressure plate has broken/ release/throwout bearing has broken?

It's difficult to see why the master cylinder should leak - unless it was incorrectly fitted in the first place?

Just to check ... The master cylinder is in the engine bay/compartment and is where you top up with clutch fluid. When a master cylinder fails it usually results in no pressure at the clutch pedal, not a leak.

The clutch slave cylinder is the one that does all the work. When you press the pedal hydraulic pressure is sent from the master cylinder to the slave cylinder - which then pushes the release/throwout bearing against the clutch pressure plate and 'disconnects' the driven plate .. allowing you to change gear.

The slave cylinder is the one that does all the hard work - it is located somewhere where engine and gearbox mate together, usually at the bottom right/left. It's usually the one that fails/leaks. It's quite easy to replace..

I don't think it is anything to do with reverse gear. It's more to do with the clutch pedal being depressed - and, I would suspect - something has failed.

The link below is generic images of a clutch:
clutch diagram Google Search

Basically, a clutch is 3 parts. There's the 'pressure plate' which bolts onto your flywheel. The pressure plate is a 'spring'. You depress the clutch pedal and the release/throwout bearing presses onto the centre of the pressure plate causing the 'fingers' - the springs - to bend back and take pressure off the driven plate - which is the link - the drive - between engine and gearbox.

If you have a leak your clutch will not work. This causes a 'grinding/crashing' noise when you try to change gear. The first thing you should do is check where the leak is coming from and do something about it.

The 'noise' that you mention may be due to the fact that the gears are 'grinding' as they try to mesh together without the use of the clutch.

The first thing you should do is check why there's a leak. It's difficult to see why a new master cylinder is leaking unless it was incorrectly fitted and damaged (pipes incorrectly connected..).

If it's the slave cylinder that is leaking - replace it. Easy job.

If Master cylinder and slave cylinder are ok - you have to look at your clutch unit. A clutch is always replaced with 3 parts ... throwout bearing/pressure plate and driven disk.

Does the car want to pull when sitting still in gear with your foot on the clutch? If so, I would say that your clutch is not fully engaging and could be the cause of your grinding when changing gears. If not then I would think the clutch is operating fully and the synchros are worn and need replaced. But either way, with metalic fluid being in the slave cylinder dust boot, the slave cylinder needs changed.

the gear grinding noise is because the clutch plate is not fully disengaging and the input shaft is still driving. If you did not use the same length of push rod then the slave cylinder is not moving enough to disengage the clutch. Check it out that with the pedal on the floor the piston in the slave cylinder should be almost to the edge of the slave cylinder . That is where It should be to be working properly

Well it's sounds like to me that the grinding sound you hear is throwout bearing, and as far as no clutch, if you don't have no clutch pedal what I mean is it don't feel lime it used to that is your slave cylinder, it needs replaced, usually when they go out they just go, don't give no warning

Hi bosslady15,

First of all I think I should say that clutches do not make grinding noises - but transmission gears do.
However, a clutch that is not disengaging properly can make the gears grind when trying to shift from one gear to the next. Also a common source of noise is the clutch throwout bearing. This will make a "grinding" or "growling" noise any time the clutch pedal is depressed. In either of these cases, the only solution is to replace the clutch, throwout bearing, pressure plate and pilot bushing. These all usually come in a clutch kit. If you have an hydraulic clutch with an internal slave cylinder it is recommended to replace the slave cylinder as well and also the flywheel on on vehicles. I'm sorry I cannot be more specific because you did not mention what type of vehicle we are talking about here.

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:
0results for isuzu rodeo clutch master cylinder overhaul kit

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

Replace the slave Cylinder as the boot just stops the dirt the seal inside does all the work. Make sure you bleed the cylinder when you are done.

The internal slave cylinder can only be accessed by removing transmission -- suggest you remove clutch assy and check before reinstalling the transmission -- you may want to replace clutch if worn down to rivets.