Can you change the thermostat only or is the housing and thermostat togather and replaced togather?

That very interesting???You did something wrong!!! I changed many thermostats never had any problems...

Since you have it off, it would make perfect sense to change it. If the water pump is leaking or is bad for another reason, thermostats also have a lifespan and, unless replaced within the last couple of years, just change it for preventative maintenance's sake. Depending on what year your truck is, the new pumps have been upgraded to solve some inherent problems. The early pumps on LS series engines had, I believe, a 2-bolt thermostat housing and the later pumps have a 3-bolt housing, so you have to change the thermostat/housing. The thermostat and housing are a combined unit and can't be separated. It seems that the cheapest part is the original AC-Delco. Most auto parts suppliers are smart about this and don't even carry an aftermarket part. The new O.E.M. AC-Delco waterpumps used to come with the stat/housing already bolted to the pump.

1. • 1 Pop the hood and locate the thermostat. It's on the passenger side of the engine and has a plug leading into it.
     
   • 2 Unplug the thermostat housing from the engine block using the 3/8-inch ratchet and socket set. The housing will come off in your hand and then you can pull out the old thermostat.
     
   • 3 Scrape off the engine block and the thermostat housing's mounting surfaces with the gasket scraper. This is to ensure the replacement gasket seals correctly.
     
   • 4 Place the replacement thermostat into the engine block and place the gasket over the ends of the bolts in the thermostat housing to keep them aligned.
     
   • 5 Bolt the thermostat housing into the engine block using the 3/8-inch ratchet and socket set.
     

Read more: How to Change the Thermostat on a PT Cruiser ' eHow.com http://www.ehow.com/how_5643178_change-thermostat-pt-cruiser.html#ixzz1g9B0K8Go

Hi.

1. Locate the thermostat housing. The housing can be found following the radiator hose toward the engine. The housing is located on the engine.
2. Remove the three screws that hold the thermostat housing.
3. Replace the thermostat.

Note. The thermostat spring goes toward the engine, the other side toward the radiator.

Here a diagram:



Regards.

Ginko

Engine Coolant Thermostat Replacement (4.2L Engine)
Tools Required
J 38185 Hose Clamp Pliers

Removal Procedure
Remove the necessary coolant from the radiator. Refer to Cooling System Draining and Filling .
Remove the generator. Refer to Generator Replacement .



Loosen the outlet hose clamp at the thermostat housing (1). Remove the outlet hose from the thermostat housing.



Remove the thermostat housing bolts.
Remove the thermostat housing from the engine block.
Clean all of the surfaces of the thermostat housing.
Clean the sealing surface of the engine block.
Installation Procedure




Install the thermostat housing to the engine block.
Notice: Refer to Fastener Notice in the Preface section.

Install the thermostat housing bolts.
Tighten
Tighten the bolts to 10 N·m (89 lb in).

Lubricate the inner diameter of the radiator hose with engine coolant.



Install the outlet hose to the thermostat housing (1). Secure the hose with the clamp.
Install the generator. Refer to Generator Replacement .
Fill the cooling system with specified coolant and concentration. Refer to Cooling System Draining and Filling .
Inspect all sealing surfaces for leaks after starting the engine.

A FAULTY THERMOSTAT STUCK OPEN WILL EFFECT GAS MILEAGE AND CAUSE POOR OR NO HEAT CONDITIONS.THERMOSTAT NOT A HARD JOB TO FIX.ALL YOU NEED TO DO IS DRAIN OUT SOME OF THE COOLANT IN A DRAIN PAN.DRAIN COOLANT LEVEL BELOW THERMOSTAT.IF YOU HAVE 3.8L ENGINE THERMOSTAT HOUSING ON TOP INTAKE MANIFOLD.IF YOU HAVE 5.3L ENGINE FOLLOW TOP RADIATOR HOSE IT WILL LEAD YOU TO THERMOSTAT HOUSING.REMOVE HOUSING THERMOSTAT INSIDE THE HOUSING.IF YOU HAVE WATER INLET ANDTHERMOSTAT IN ONE COMPLETE UNIT OR HOUSING YOU HAVE TO REPLACE THE ENTIRE WATER INLET HOUSING WITH NEW THERMOSTAT.THIS TYPE UNIT WILL HAVE LONG PIPE WITH BYPASS PIPE WITH WATER INLET WITH THERMOSTAT. ONCE YOU REPLACE THERMOSTAT.IF YOUR RED ARROWS OFF AND HEAT STILL DONT WORK THE DEALERSHIP WILL HAVE TO CHECK IT OUT.WITH NEW THERMOSTAT AND PRESSURE CAP.MAKE SURE GET COOLANT LEVEL CORRECT.SEE HOW HEAT WORKS.IF NOT YOU HAVE A ELECTRICAL PROBLEM AT AC AND HEATER CONTROL SWITCH.

Locate the water hose at the top of the radiator and follow it to the top of the engine block. There you will find the thermostat housing. Remove the two bolts and remove the housing. Pay attention as to how the thermostat is sitting in the housing. Lift it out and put in the new thermostat the same way. Make sure you replace the thermostat housing gasket. Reassemble the housing and add anti-freeze until full.

The thermostat is inside a black plastic housing, It is inside the housing assembly where both radiator hoses meet up by the engine. You can't replace just the thermostat, the whole housing has to be replaced,

The dealership will charge around $450 to change the thermostat on the 3.4L engine.
You have to remove the crossover exhaust manifold. Once that is out of the way, the thermostat itself is easy. Before the manifold is removed, I could only touch one of the two bolts holding the thermostat housing in place, much less get a wrench on it.

If your engine is the 3.4L then the instructions below will work:

REMOVAL: - Remove the air cleaner and duct assembly. - Drain the coolant until the coolant level is below the thermostat. - Remove the crossover exhaust pipe. - Remove the radiator hose from the thermostat housing. - Remove the thermostat housing bolts and clean any sealer from the bolt threads.


(IMAGE: Removing the housing bolts)

- Remove the thermostat housing and gasket. - Remove the thermostat. - Clean the mating surfaces.

(IMAGE: The removal and installation of the thermostat)

INSTALLATION: - Install the thermostat.Install the thermostat housing and gasket.

NOTE: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

- Install the thermostat housing bolts and tighten them to 18 ft. lbs. (25 Nm). - Install the radiator hose to the thermostat housing.Install the crossover exhaust pipe. - Install the air cleaner and duct assembly. - Fill the cooling system.

Hope this helps, happy holidays :)

Engine Coolant Thermostat Replacement (4.2L Engine)
Tools Required
J 38185 Hose Clamp Pliers

Removal Procedure
Remove the necessary coolant from the radiator. Refer to Cooling System Draining and Filling .
Remove the generator. Refer to Generator Replacement .



Loosen the outlet hose clamp at the thermostat housing (1). Remove the outlet hose from the thermostat housing.



Remove the thermostat housing bolts.
Remove the thermostat housing from the engine block.
Clean all of the surfaces of the thermostat housing.
Clean the sealing surface of the engine block.
Installation Procedure




Install the thermostat housing to the engine block.
Notice: Refer to Fastener Notice in the Preface section.

Install the thermostat housing bolts.
Tighten
Tighten the bolts to 10 N�m (89 lb in).

Lubricate the inner diameter of the radiator hose with engine coolant.



Install the outlet hose to the thermostat housing (1). Secure the hose with the clamp.
Install the generator. Refer to Generator Replacement .
Fill the cooling system with specified coolant and concentration. Refer to Cooling System Draining and Filling .
Inspect all sealing surfaces for leaks after starting the engine.