The water pump is responsible for sending coolant to the engine. Removing and installing a water pump in a PT Cruiser is a complex task. Due to the small engine space, the timing belt and other components block access to the pump's mounting location on the engine. The exact method of installation will vary depending on the year of the Cruiser and the type of engine it contains. Consult with your mechanic before you take on this task.
Take the PT Cruiser to an automotive air conditioning shop to have the refrigerant discharged by a licensed technician.
Disconnect the PT Cruiser's negative battery cable.
Open the drain fitting on the radiator and drain the engine coolant into a container capable of holding at least 12 quarts.
Raise the car's front end and support it on jack stands. Remove the right front wheel and the drive belt splash shield; the shield's fastener's should take a Torx wrench.
Loosen the drive belt tensioner with a socket wrench and remove each drive belt, taking note of which belt is for which component -- the power steering pump/compressor or the alternator.
Turn the crankshaft using a breaker bar and socket on the bolt in front of the crankshaft until the arrow on the timing belt pulley is pointing up at the 12 o'clock position.
Unbolt and remove the front timing belt covers, the timing belt, the camshaft sprockets and the rear timing belt cover.
Unscrew and remove the water pump's bolts with a wrench using a criss-cross pattern. Remove the pump from the cylinder block. Tap it with a soft-face hammer to break the seal if needed.
Clean all corrosion and sealant from the bolt threads and scrape away all gasket traces from the cylinder block using a gasket scraper.
Apply a new O-ring and a thin film of RTV sealant to the inner flange of the new water pump body.
Connect the new pump to the engine and install the bolts, making sure you don't over-tighten the bolts.
Reconnect all the timing belt covers, the camshaft sprockets and the timing belt.
Re-install the drive belts, making sure they each follow the same path as before.
Reconnect the drive belt splash shield and the wheel and lower the car.
Reconnect the battery cable.
Connect a tube to the thermostat's bleeder valve, submerge the other end in a container of coolant and loosen the bleed screw. Refill the radiator with the engine coolant until you reach the pressure cap seat and no bubbles come out the tube. Close the screw.
Return the car to the shop to have its air conditioner evacuated and recharged.
Use fresh coolant and water if the old mixture is contaminated. Use the same type of engine coolant that was originally used. Many PT Cruisers use Mopar 5 year/100,000-mile coolant. Check the manual.