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Discussion Starter · #1 ·
Bought the car at 53k miles last year. I changed out the ATF since it was burned out but didn't change the filter. Still doing the regular oil change interval plus new tires. Last week, I did a road trip with my family to Arizona. It's at 56k miles on it. On the way to I-40 from Las Vegas, there weren't any issue at all. A/C was at max, temperature gauge was normal. However when heading back, whenever I hit a hill that's +5% grade or higher, my engine gauge would start going up gradually to red. Only when I stayed at or under 45 mph does the gauge not go up. Upon parking the vehicle in the shoulder to avoid overheating (did it three times), the gauge would go back to the middle within 5-10 minutes. While driving downhill or flats, it remained on normal temperature even at speeds of 80 mph. No issues, with the A/C the whole time when this was happening. Had it at max setting on circulation. Only remember this cause my wife was complaining that it was cold inside the car.

I'm considering actually taking care of ATF filter and perform a complete coolant & ATF flush as a start. It doesn't seems to be water pump or a thermostat issue since my car remained at normal temperature on my regular driving route/errands (including on hills).

Planning on using (Please let me know reasonable alternatives as well)
1. Prestone DEX-COOL Concentrate
2. Distilled water
3. Castrol Transmax Dexron VI Transmission fluid - Quarts. (Considering Castrol Transmax Dex/Merc -Gallons)
4. RPT Shift Pro Transmission Filter (A/T) 997142

Do you think is this a good start to take care of this odd overheating issue? Any recommendation or suggestions?
 

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Must be more to the story....the vehicle is overheating and you're focused entirely on the transmission. What am I missing?
 

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Discussion Starter · #3 ·
Must be more to the story....the vehicle is overheating and you're focused entirely on the transmission. What am I missing?
Only had one CEL that I took care of. P0455 was the code. Gross Evap code issue. Changed out the canister purge valve. CEL been off for over 700 miles.
 

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Through time the radiator core builds up deposits inside which reduce the flow of coolant and the amount of heat the system can reject. Under normal circumstances the cooling system will be just fine. But when a stern test is applied (e.g., going up a grade with family in car and AC on in the desert heat), the cooling system cannot reject all the heat being created. My 2004 3.8L has the same issue when driving up to operating temperature and then you stop at a red light. Until you start moving again, the temperature begins creeping upward.

I am planning to flush the cooling system and replace the coolant with new. It will help but it's not clear if it will help enough. You might want to try the same. If flushing does little and the problem becomes worse, then it's time for a new radiator. At least that's my assessment.....
 

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Through time the radiator core builds up deposits inside which reduce the flow of coolant and the amount of heat the system can reject. Under normal circumstances the cooling system will be just fine. But when a stern test is applied (e.g., going up a grade with family in car and AC on in the desert heat), the cooling system cannot reject all the heat being created. My 2004 3.8L has the same issue when driving up to operating temperature and then you stop at a red light. Until you start moving again, the temperature begins creeping upward.

I am planning to flush the cooling system and replace the coolant with new. It will help but it's not clear if it will help enough. You might want to try the same. If flushing does little and the problem becomes worse, then it's time for a new radiator. At least that's my assessment.....
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I am having this same type of problem. I have a 2003 Impala with the 3.4 l8tr engine. The engine only shows over heating when it has been run for a while, and only when the RPS are increased like when going uphill. We have replaced the thermostat, radiator, lower radiator hose and the sensor. Of course when we changed the radiator then we put all new fluid in it as well but this continues to happen. No idea what to try now except maybe change the catalytic converter or muffler in case they are partially plugged since the engine codes keep saying something is up with the O2 sensors.
 

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Through time the radiator core builds up deposits inside which reduce the flow of coolant and the amount of heat the system can reject. Under normal circumstances the cooling system will be just fine. But when a stern test is applied (e.g., going up a grade with family in car and AC on in the desert heat), the cooling system cannot reject all the heat being created. My 2004 3.8L has the same issue when driving up to operating temperature and then you stop at a red light. Until you start moving again, the temperature begins creeping upward.

I am planning to flush the cooling system and replace the coolant with new. It will help but it's not clear if it will help enough. You might want to try the same. If flushing does little and the problem becomes worse, then it's time for a new radiator. At least that's my assessment.....
I think if you turned on the heat to max when you started to over heat you may reduce the over heating. If this did occur then I would say to flush out your radiator because it cannot handle the heat load. this is how I determined that I needed a new radiator after flushing did not do the trick. Good Luck
 

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I think if you turned on the heat to max when you started to over heat you may reduce the over heating. If this did occur then I would say to flush out your radiator because it cannot handle the heat load. this is how I determined that I needed a new radiator after flushing did not do the trick. Good Luck
My car doesn't actually get up to the red yet but it does get close. I put a brand new radiator in it just about a month ago. It's not the radiator being plugged up. Plus, I really don't want to turn on the heat inside my car when it's already over 100° outside!
 

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You did not mention the thermostat. It is first on the list, along with coolant level.

Filter should be changed when you change fluid. And burnt fluid means burnt transmission clutch(es).
 
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