I have a 97 cavalier with a 2.2L. It is over heating and the low coolant light will not go out. I have replaced the thermostat, radiator, radiator cap, serpentine belt, water pump, and transmission cooling lines to the radiator. But it is still over heating. I noticed that the upper hose is warm/hot to the touch, but the lower hose is still cool. I took out the thermostat and tested it in boiling water and it opens up. I drove my car without the thermostat and it doesn't over heat. I cannot go with out heat though. Any thoughts?

Are you saying the engine is cold but the gauge on the dash is saying the coolant is very hot ?
If the engine is cold, the problem could be the gauge or the sending unit.
If the engine is getting hot, the problem could be the radiator is low on coolant or has air in the system, or the water pump is not working.

Hi,

Check the sensor and wiring from it for a short.

Hope this is an easy fix for you.

If your not low, and your not overheating, chances are that the level sensor is either dirty, or faulty. It's located in the coolant resevoir.

A code P0128 may mean that one or more of the following has happened:

• Low engine coolant level
• Leaking or stuck open thermostat
• Faulty cooling fan (running too much)
• Faulty coolant temperature (ECT) sensor
• Faulty intake air temperature (IAT) sensor

Possible Solutions

Follow the top radiator hose to where it connects to the engine, there should be a metal removable housing there with the thermostat inside. Be sure to replace the gasket after installing a new thermostat and also be sure the thermostat is placed in the correct direction for coolant flow.

the simplest fix is to check your coolant level, if the radiator is low enough your heat wont come on. when the car is warmed up, switch the engine off and check the level in the over flow bottle (located on the passager side) first squeeze the upper radiator hose with a shop towel to check for back pressure. if theres too much pressure wait for the engine to cool down longer. using the towel again remove the overflow cap, the bottle is pressurized so do so slowly to allow any stem to escape without burning you. if the coolant bottle is low, topoff with DEXCOOL (GM approved coolant)
once bottle is at the 'full hot' line replace cap and start car back up and switch heat on high/defrost. odds are decent this will fix the issue,
and it will only cost you a bottle of antifreeze :)

First, look for leaks and make certain your radiator and overflow are full-do you have heat? If not, you may have a closed thermostat. If you have antifreeze in your oil, or notice smoke coming out of your tailpipe when the car is fully warmed up, you may have a blown head gasket.

GM Cavalier/Sunfire 1995-2000 Repair Guide

Thermostat - REMOVAL & INSTALLATION

2.2L Engine
(see Figures 1, 2, 3, 4, 5 and 6)


Fig. 1: The thermostat is located in the lower radiator hose on the 2.2L engine


Fig. 2: Remove the two retaining bolts for on the housing


Fig. 3: Separate the housing halves to access the thermostat


Fig. 4: Pull the thermostat out to remove it from the housing


Fig. 5: The thermostat has an O-ring which goes around the center


Fig. 6: Thoroughly clean the mating surfaces of the thermostat housing
When adding coolant, it is important that you use GM Goodwrench DEX-COOL® (orange colored, silicate free) coolant meeting GM specifications. On these vehicles, if silicated coolant is added to the system, premature engine, heater core or radiator corrosion may result. In addition, the engine coolant will require change sooner; at 30,000 miles or 24 months.

1. Disconnect the negative battery cable.
2. Properly drain and recover the coolant until the level is below the thermostat.
3. Unfasten the coolant outlet-to-inlet manifold attaching bolt and nut, then remove the outlet.
4. Remove the thermostat. Clean the inlet manifold and outlet mating surfaces.

To install:

1. Install a new O-ring onto the thermostat
2. Place the thermostat in the inlet manifold.
3. Attach the coolant outlet to the inlet manifold, using the bolt and nut. Tighten to 89 inch lbs. (10 Nm).
4. Refill the engine cooling system.
5. Connect the negative battery cable, then start the engine and check for coolant leaks.

Hope this helped (remember comment and rated this).

SOUND LIKE THERMOSTAT FAULTY.

Would have to suggest water pump at this point if all else has failed.