Mechanics

CHEVY ENGINE OVERHEATING

2002 Chevrolet Impala

Engine Cooling problem
2002 Chevy Impala 6 cyl Two Wheel Drive Automatic 93000 miles

I bought this car in January of 2009 and since then it has been overheating constantly. Thankfully I don't need to drive it everyday, but I have put a hefty sum of cash into the vehicle and was hoping someone could give me the best prognosis for my problem.

First note - In the winter the car barely overheats, I assume due to the weather outside.

When does it overheat -
After 40 minutes of driving 65 mph +
Stop and go traffic
Idling

What I have fixed/done -
New thermostat/Radiator fan/Multiple Heater core and Radiator line flushes/had Head gasket checked, came back negative

Other symptoms -
The heat in the car will stop working and I will get a heater core flush hopefully to allieviate backed up hot air, not sure if this can cause overheating

After flushing out the radiator it appears to help, but uncertain, most machanics say that there is build up and sludge, one said it was rust piling up in the lines (is there something I can buy to get rid of the rust?)

The coolant can be murky, but does not smell like oil

Whats next -

I just don't know what it could be anymore, flushes seem to work, but that could be the introduction of new coolant into the system and very temporary. Could it be the intake manifold, which I read is bad on this model car, how would I check that?

Any other suggestions?

Thanks!
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DP978
May 27, 2010.



Hi DP978,

Thank you for the donation.

When overheating occurs and the radiator fans do not stop after starting, then the cooling efficiency is poor. Possible causes are : 1. Weak water pump.
2. Clogged radiator, normal flushing would not help, you need to remove the raditor to get the core internal lines cleared.
3. Bad thermostat. It is not opening sufficently.
4. Cooling fans not working.
5. Insufficient coolant in system.

Coolant should not be mixed, ie. Different brands in the system can cause clogging.

If the coolant is murky, it means the system could be clogged somewhere or has a lot of contaminants in it. One of the best way to check fior clogging and the condition of the coolant flow is to remove the thremostat and run the engine. If you can see the coolant flowing fast in the system then the water pump should be ok.

Let the engine run and replace the coolant with water to clear out any contaminant. Repeat a few times, each time allowing the water in system to heat up, which will then be able to clear the contaminants. A good radiator flush would help. It would be best to do the flushing over a period of a few days (without the thermostat to check if it is the cause).

Once the water in the system loooks clean, you can proceed to replace with coolant if it is not overheating.

KHLow2008
May 30, 2010.
Thank you for the response -

Can I ask a couple simple follow ups - I am by no means a mechanic or gifted when it comes to anything cars.

Just a few weeks ago I got both 1. A radiator flush and 2. My Coolant drained and replaced (so there should be no issue of mixed coolant brands).

After a couple of drives the coolant under the radiator cap is green with lots of specks of brown (does not smell like our) which a am assuming is rust or something that is making it murky.

Although I am not sure I would know how to 'remove the thermostat', I would want to check the flow of coolant, but how would I go about seeing if the coolant was 'flowing fast' or not? (Would I undo the radiator cap and see if anything flowed in there?)

Also, regarding your last paragraph about flushing it out with water, how would I go about replacing the coolant? Would I let the coolant spill out the radiator cap and pour in water in replacement? Or would I drain the coolant sommeplace else and put in water as it runs?

Edit: Should the fans come on immediately when the AC is turned on? It appeared that they were not turning, they are visible from the back of the radiator, correct? (The car was running at 220 f at this point)

Thanks for your help, I will definately be able to donate more once I am closer to some sort of answer.

Tiny
DP978
May 30, 2010.
The brown specks are an indication of contaminants and it could be rust or other foreign materials.

As to the overheatng, if the cooling fans are intermittently coming on and off, it could be caued by the Body Control Module or the charging system. There was a service bulletin out on this problem so I would suggest testing/checking if the cooling fans are working correctly as you have done the flushing so many times before.

Get the charging system tested to see if it is good.

The cooling fans should come on when the AC compressor is running. For some models there might be a slight deley at initial startup.

To flush with water, you would need to drain the coolant ut and refill with water.

To remove the thermostat, you would need to remove the thermostat housing located in fron of engine.

KHLow2008
May 31, 2010.