Car acting like engine is overheating

Tiny
TANNER1234
  • MEMBER
  • 2000 CHEVROLET IMPALA
  • 3.4L
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 172,000 MILES
So I have a 3400 model and I recently purchased the car for cheap due to the previous owner trouble shooting and not being able to find the problem with elimination I have narrowed it down to being something with the cooling system of the car. It acts like it is overheating, the overflow tank fills up to the top and the coolant gets hot, however if I drive with the heater on this issue does not occur as if it is overheating. The temperature gauge stays normal and fluctuates as it should never going over halfway no matter how long the drive. 150 on all cylinders, the car is fine and runs smoothly, just this little hiccup with the cooling system, can anybody help me find out what it is exactly? Thanks
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Monday, June 19th, 2017 AT 10:07 PM

9 Replies

Tiny
CARADIODOC
  • EXPERT
Inspect the cooling fins on the radiator to see if they are badly corroded. That will prevent them from giving up the heat to the air. The clue is running the heater reduces the overheating. The heater core is a small radiator.

A leaking cylinder head gasket is always a good suspect too, but you would be losing coolant, and you did not mention that observation.
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Monday, June 19th, 2017 AT 11:50 PM
Tiny
TANNER1234
  • MEMBER
All gaskets are brand new and nothing else is having issues at all, car is smooth as heck. Basically the only problem I am having is the overflow tank overflowing literally. Lol. Also, the low coolant light comes and goes but definitely not out of coolant. I have been told it could be the thermostat, water pump and some sensor within the cooling system. Any other thoughts or possibilities?
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Tuesday, June 20th, 2017 AT 12:10 AM
Tiny
TANNER1234
  • MEMBER
Also one final helpful hint to the issue maybe. No codes pop up on my reader and it works fine if that helps. No codes read.
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Tuesday, June 20th, 2017 AT 12:16 AM
Tiny
CARADIODOC
  • EXPERT
You said the problem does not occur when the heater is on. That eliminates the thermostat and water pump. Everything is working properly at that point.

The only other thing you did not mention is if the radiator fan is turning on. Your model should still have two coolant temperature sensors. One is for the dash gauge. That one will not cause an overheating problem. It only reports coolant temperature. The other sensor is for the engine computer. Both of them are extremely reliable because they have just one part inside them, but corrosion on connector terminals, or other wiring problems can cause it to report a temperature that is too low, then the computer will not turn the fan on. The clue to that is the overheating will never occur at highway speeds where natural air flow is sufficient.
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Tuesday, June 20th, 2017 AT 12:31 AM
Tiny
TANNER1234
  • MEMBER
So then your saying the problem pretty much has to be either the second sensor you mentioned or the radiator fans? I have considered the fans as the issue, however they somewhat seem to work, but in my opinion very poorly. Is this something you would bet on? Because I am clueless at this point. Lol, just do not want to waste the money on something that will not solve the issue. You have been very helpful and I appreciate your time though.
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Tuesday, June 20th, 2017 AT 12:39 AM
Tiny
CARADIODOC
  • EXPERT
That was not a typo. Check the cooling fins, not the fans. If you can get to the front of the radiator without the AC condenser being in the way, rub your fingertips over the fins and see if they crumble like a rotten chocolate chip cookie. This is especially common if you live in a state like I do where they throw a pound of salt on an ounce of snow.

This happened to my 1988 Grand Caravan when it was twelve years old. The temperature gauge would start to creep up at anything over sixty mph and sixty degrees. I drove it from Wisconsin to Denver, but it was mostly night driving when the temperature was cool, so I did not have a problem. By two yeas later, it even ran too hot when it was thirty five degrees. The fan turned on like it was supposed to, but the air flow did not do anything.

I used that van to drag around a tandem-axle enclosed trailer that was bigger and heavier than the van, and with that radiator, I could keep the temperature down by running the front and rear heaters on high. Problem was I was taking that trailer to the nation's second largest old car show swap meet which is always the first weekend after the Fourth of July, so it is always hot outside. Running the heaters is not what you want to do on a hot summer day! I finally had to get a new radiator. I patched so many holes in it that I was spending more time at that than sleeping! With the new radiator, the temperature stayed normal, even when pulling that trailer on a hot day.
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Tuesday, June 20th, 2017 AT 1:31 AM
Tiny
TANNER1234
  • MEMBER
The car did originally come from Nebraska in fact. Okay, you have been very helpful good sir thanks for your time and information man I appreciate it.
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Tuesday, June 20th, 2017 AT 1:36 AM
Tiny
TANNER1234
  • MEMBER
I have inspected the radiator and it is also fairly new. Very clean. So now I am back at square one. Lol, help! I am stumped at this point. The only thing I can think of is the second sensor this mechanic mentioned, does anyone else have any opinions?
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Tuesday, June 20th, 2017 AT 11:33 AM
Tiny
CARADIODOC
  • EXPERT
Next I would perform a chemical test at the reservoir to check for a leaking cylinder head gasket. That involves drawing air from the reservoir, while the engine is running, through a glass cylinder with two chambers partially-filled with a special dark blue liquid. If combustion gases are present, the liquid will turn bright yellow.

It may be less expensive to have your mechanic do this test. You might be able to borrow the tester from an auto parts store that rents or borrows tools, but they typically make you buy your own bottle of liquid That is because the liquid is rendered ineffective if it is allowed to freeze or if it becomes contaminated with coolant. That would cause it to provide incorrect results for the next person who borrows it. The test usually only takes a few minutes. A bottle of the special liquid may cost more than the cost of the test.
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Tuesday, June 20th, 2017 AT 8:12 PM

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