Did you bleed the air out of the hydraulic system after changing the wheel cylinder? If not, you must do so.
On a Chevy Cavalier, the low pressure switch is located under the hood on the passenger side, next to the radiator. It is situated near the top corner of the radiator.
You should have someone look at your master cylinder,sounds like the diaphragm has a hole in it.
If it is a six cylinder the low pressure fill is on the passenger side near the firewall.
It may be that your clutch master cylinder is bad, or more than likely one of the internal components within the cylinder, have the clutch master cylinder checked.
For the 2.0 4 cylinder it should be 9-13 psi, with a minimum of 13 psi deadhead pressure. With the 2.8 liter 6 cylinder it should be 5.5 to 6.5 psi at idle, there is no deadhead specification. Deadhead pressure is pressure at idle with the return line pinched off.
The lower rear part of the engine. You will see it from the passenger side on the bottom half of the engine in the back. added fact: the seat for this is plastic. Most oil leaks for the straight four cylinder engine starts here. You will see a puddle in the middle of the engine on the driveway.
The 6 cylinder oil pressure switch is located on the passenger side rear of the block. It is a single wire connection with a gray/yellow striped wire
The oil pressure switch on a 1996 Chevrolet Cavalier is on the rear of the engine block. It will be directly above the oil pan.
passenger side on the firewall underneath the black plastic wiring cover, aluminum cylinder and low pressure valve. takes lots of looking and if amateur then have a pro do it
7.5 psi
The Air conditioner low pressure stem is on the accumulator (silver cylinder), which is next to the firewall on the passenger side of the engine compartment.
It is on the top of the accumulator. That is the large metal cylinder under the hood, passenger side.