I have 2002 impala with 3.4 engine. i have a problem with the engine over heating. i replaced the water pump thermostat radiator and cooling fans and it still runs hot. What's strange is the temperature gauge reads hot and then goes down to cool and then back up to hot a again. Do you have any idea of what my problem is?

Here is a general diagram of the cooling system for a 2003 Chevrolet Impala:
[Diagram of 2003 Chevrolet Impala cooling system]
In this diagram, the main components of the cooling system are labeled as follows:

1. Radiator: This is a heat exchanger that is responsible for dissipating heat from the engine coolant.
2. Radiator fan: This is a fan that helps to cool the radiator by blowing air through it.
3. Thermostat: This is a valve that controls the flow of coolant through the engine and radiator based on the temperature of the engine.
4. Water pump: This is a pump that circulates the coolant through the engine and radiator.
5. Engine block: This is the main component of the engine, where the combustion process takes place.
6. Head gasket: This is a gasket that seals the engine block and cylinder head, allowing the coolant to flow through the engine.
7. Cylinder head: This is a component of the engine that covers the top of the cylinders and contains the valves.
8. Heater core: This is a small radiator that is responsible for heating the interior of the vehicle.

I hope this information is helpful! If you have any further questions or need more detailed information about the cooling system for your 2003 Chevrolet Impala, you may want to consider consulting with a mechanic or referring to the vehicle's owner's manual.

have a compression test done to check for head gaskets/cracks. check thermostat fitted correctly. If there is a viscous fan hub then replace it. if the bottom hose stays cool that indicates a blockage and that if the radiator is off the shelf new points to a thermostat fitted the wrong way . over haeting at lights goin slow or working at high rpms while loaded points to the fan hub. If electric fans then it points to the fact that they are not coming on. check ignition timing as a spark after TDC will cause overheating.. If at speed it over heats then check over drive operation as over reving the engine will also over heat the engine.

Have you had the radiator serviced and the thermatic fan oil checked? The radiator may be blocked and if the thermatic fan is faulty It wont lock up to cool your engine.

The most common overlook thing is you got a air pocket, so before you go spend your money turn Heather on full blast, open the radiator cap, car running look for air bubbles, takes patience cause you got to wait for the thermostat to open up, you must refill the coolant really really slow snail pace, some car have a bleeding valve others have two chamber on the overflow bottle,good luck, if that doesn't work change the thermostat first and if that doesn't work I'm afraid you may need to replace water pump. . water pump

Hi,
Am trying to understand the problem, but it really needs some details, like when the car stops( engine running ) the temperature cools down?

Give us more!

You probably need to bleed the cooling system properly.

Open the cooling system bleeder screws.

Slowly fill the cooling system with a 50/50 coolant mixture until coolant runs freely out of bleeder screws.
Close the cooling system bleeder screws
Install the coolant pressure cap
Start the engine.
Run the engine at 2,000 - 2,500 RPM until the engine reaches normal operating temperature. (midway on gauge)
Allow the engine to idle for 3 minutes.
Shut the engine off.
Allow the engine to completely cool.
Top off the coolant as necessary.
Run engine again at 2000 - 2500 RPM until the engine reaches normal operating temperature.
Allow engine to idle until cooling fans come on. It should come on with the gauge about 3/4 of the way to red. - if it gets to where is touches the red, shut down immediately.
When the fan comes on, put your hand behind the fan and observe the temperature of the air coming from the fan. It should feel hot. If it is blowing cold air, the coolant is not circulating through the radiator like it should. This could be caused by lots of things including an improper/defective thermostat, corroded water pump impeller, or a blown head gasket.

Thermostats in cars are often neglected, if not totally forgotten, units. Yet they play an important role in the general performance of cars by restricting water flow until the engine has warmed-up. Thermostats are heat sensitive valves that open and close. On cars they prevent circulation of coolant to the radiator until the engine is warm enough. When the thermostat is closed water only flows through the water pump and water jacket to let the engine warm quickly. When the thermostat opens, water can then pass through the radiator for general cooling.
google_protectAndRun("ads_core.google_render_ad", google_handleError, google_render_ad); Having a car that warms quickly is particularly useful in cold weather when you want to use your car heater as soon as possible. The thermostat is in a small housing positioned where the top radiator hose connects to the engine. The best time to check or change a thermostat is when you are servicing your radiator because you need to drain the cooling system
first. Hence, a thermostat change is a good time to flush and clean your cooling system, check all radiator hoses and the radiator pressure cap. Be sure you have the correct cap on your radiator and it is not rusted. Thermostats are small, inexpensive items. You can test them by heating in water and checking their operating temperature with a thermometer. However it really is quicker and ultimately more reliable to simply fit a new one,
1. thermostat common problems (replace every 50-60k miles)
2. thermostat switch sensor (which turn your cooling fan on and off)
3. check and see if the cooling fans is running when the engine get to its operation temperature. (fan motor can be fault)

No smoke good cooling system is sealed, could be a thermostat, sticking or radiator fan not coming on, does it start to over heat at stops or low speeds, if so have your radiator fan check out, if it over heats at any speed, replace thermostat and check coolant level.

I recommend flushing the radiator thoroughly if not done recently. there seems to be some sort of blockage in the radiator at this time. if you get lots of metal fragments that are flushed out during this flush, i will then recommend a rebuild on the radiator or replacement of the radiator. make sure the cooling fans are cycling on time as well.

The engine is kept cool by a liquid circulating through the engine to a radiator. In the radiator, the liquid is cooled by air passing through the radiator tubes. The coolant is circulated by a rotating water pump driven by the engine crankshaft. The complete engine cooling system consists of a radiator, recovery system, cooling fan, thermostat, water pump and serpentine belt.

Check the coolant level in the recovery bottle or surge tank, usually mounted on the inner fender. With the engine cold, the coolant level should be at the FULL COLD or between the FULL HOT and ADD level. With the engine at normal operating temperature, the coolant level should be at the FULL HOT or HOT mark. Only add coolant to the recovery bottle or surge tank as necessary to bring the system up to a proper level. On any vehicle that is not equipped with a coolant recovery bottle or surge tank, the level must be checked by removing the radiator cap. This should only be done when the cooling system has had time to sufficiently cool after the engine has been run. The coolant level should be within 2 in. (51mm) of the base of the radiator filler neck. If necessary, coolant can then be added directly to the radiator.

While you are checking the coolant level, check the radiator cap for a worn or cracked gasket. If the cap doesn't seal properly, fluid will be lost and the engine will overheat.

Worn caps should be replaced with a new one.

Periodically clean any debris; leaves, paper, insects, etc. from the radiator fins. Pick the large pieces off by hand. The smaller pieces can be washed away with water pressure from a hose.

Carefully straighten any bent radiator fins with a pair of needle nose pliers. Be careful, the fins are very soft. Don't wiggle the fins back and forth too much. Straighten them once and try not move them again. It is recommended that the radiator be cleaned and flushed of sludge and any rust build-up once a year. If this has not been administered within the stated time, this may be why your vehicle is overheating at this time. Have the Radiator flushed asap if this is the case.

Now, if the coolant level is proper and, the cap is in fair or good condition, i would advise to move in the direction of the cooling fans and sensors as well. These fans are vital to the cooling process as well. The cooling fans must cycle in intervals to keep the coolant cool during stop and go driving or, long idle. They are also very important during the operational period of the AC during travel as well. i recommend inspecting the cooling fans while the engine is running. they should cycle during the running period. if thsi is not the case, you will need to test the operational value of these devices. The test procedure follows below


TESTING


1. If the fan doesn't operate, disconnect the fan and apply voltage across the fan terminals. If the fan still doesn't run, it needs a new motor.

2. If the fan runs, with the jumpers but not when connected, the fan relay is the most likely problem.

3. If fan operates but a high current draw is suspected continue with the following ammeter TESTING.

4. Disconnect the electrical connector from the cooling fan.

5. Using an ammeter and jumper wires, connect the fan motor in series with the battery and ammeter. With the fan running, check the ammeter reading, it should be 3.4-5.0 amps; if not, replace the motor.

6. Reconnect the fan's electrical connector. Start the engine, allow it to reach temperatures above 194°F and confirm that the fan runs. If the fan doesn't run, replace the temperature switch.



Ok, Now we will move on to the next possible issue. The water pump. ok, due to the fact that your pump is driven by the drive belt, you will need to start the engine and listen for bad bearing, using a mechanic's Stethoscope or rubber tubing.

* Place the stethoscope or hose on the bearing or pump shaft.
* If a louder than normal noise is heard, the bearing is defective.

Replace the pump in this case.

You will also notice leakage around the pump housing if the seal has failed as well. this will strain the impeller and, ruin the pump.

Now. the last area of concern will be the thermosta. this is the most common issue that will inflict overheating in many vehicles. The thermostat is used to control the flow of engine coolant. When the engine is cold, the thermostat is closed to prevent coolant from circulating through the engine. As the engine begins to warm up, the thermostat opens to allow the coolant to flow through the radiator and cool the engine to its normal operating temperature. Fuel economy and engine durability is increased when operated at normal operating temperature.


There are several ways to test the opening temperature of a thermostat.

One method does not require that the thermostat be removed from the engine.

* Remove the radiator pressure cap from a cool radiator and insert a thermometer into the coolant.
* Start the engine and let it warm up. Watch the thermometer and the surface of the coolant.
* When the coolant begins to flow, this indicates the thermostat has started to open.
* The reading on the thermometer indicates the opening temperature of the thermostat.
* If the engine is cold and coolant circulates, this indicates the thermostat is stuck open and must be replaced.

The other way to test a thermostat is to remove it.

* Suspend the thermostat completely submerged in a small container of water so it does not touch the bottom.
* Place a thermometer in the water so it does not touch the container and only measures water temperature.
* Heat the water.
* When the thermostat valve barely begins to open, read the thermometer. This is the opening temperature of this particular thermostat.
* If the valve stays open after the thermostat is removed from the water, the thermostat is defective and must be replaced.
* Several types of commercial testers are available. When using such a tester, be sure to follow the manufacturer's instructions.
* Markings on the thermostat normally indicate which end should face toward the radiator. Regardless of the markings, the sensored end must always be installed toward the engine.
* When replacing the thermostat, also replace the gasket that seals the thermostat in place and is positioned between the water outlet casting and the engine block.

* Generally, these gaskets are made of a composition fiber material and are die-cut to match the thermostat opening and mounting bolt configuration of the water outlet.
* Thermostat gaskets generally come with or without an adhesive backing. The adhesive backing of gaskets holds the thermostat securely centered in the mounting flange, leaving both hands of the technician free to align and bolt the thermostat securely in place.