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Hello my friends. I am from Honduras and I am happy with my Chevy Impala 2008. I acquired the car 4 years ago from my uncle who never did any type of fluid change. The brake fluid was black with the reservoir covered with a plastic bag because the cap was lost several years ago. The power steering fluid was black. And I made the mistake last year to drain the coolant (I tougth was original Dexcool never changed from the factory) and put cheap green coolant. Because of that two months later my heater pipe broke from corrosion in March, so I lost all the coolant and had a overheating. I repair the leak and the mechanic put tap water inside. I couldnt get Dexcool here in my city in that time. So I got 4 gallons a week ago, and did 5 flushes with distilled water and after that filled the system with Dexcool. I made a 238 mile trip the same day without issues. The next day after the trip I turn on the car and drive 0.5miles and the engine overheated, I shut off the car, opened the hood and for my surprise the engine has no coolant in the system. I check under the hood and notice a leak in the drivebelt side and I supposed the water pump was broken and possibly it made the cooling system lost all the new Dexcool. After I let the engine cool I filled the system with tap water, return to my home and the next day I was making the call to tow my car when I opened the radiator cap and put a little amount of water. For my surprise the system was 95% full with the water I put last day. The leak disappear, but I had no confidence in my car with the previous overheat. So I got my car to the mechanic to put a new water pump. The mechanic got the old water pump out, which looks like this:

Automotive tire Motor vehicle Crankset Automotive lighting Rim


Bicycle part Vehicle brake Rim Bicycle chain Electric blue



I ordered the mechanic to change my thermostat and look for aditional leaks. This was the condition of the old thermostat:

Head Liquid Musical instrument Art Astronomical object


Hand Wheel Fluid Finger Automotive tire


My mechanic´s opinion was that the thermostat was good, but I asked him to change it anyways.

So, the mechanic changed the water pump, changed the thermostat and filled the system with Dexcool. I test the system and everything was ok.

Today I drived the car from cold start in the morning, checked the coolant level that was good, and drive for 2 miles and the gauge marked the engine was at optimun temperature in the middle. I got scared because that was so quick that I thougth the engine would overheat again. I drive slowly the remaining 3 miles to my job and the needle in the gauge doesn´t move. When I came from my job take the time to the engine heat. The engine got normal temperature in the same 2 miles without overheating. I checked my coolant temperature with a scanner and the thermostat open in 217.4F, with my engine operating in a temperature between 200.5-217.4F. Before when the system was running in tap water I could drive almost 15 miles until the engine got operating temperature.

My questions are: Is this normal? Is Dexcool the cause of this? Is my radiator bad? Is normal this operating temperature in my car, the specifications in the thermostat said it open in 185F degrees?
 

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Good day enthusiast.
The coolant temp during operation will heat up to 185 to 210f or a bit more depending on ambient temperature.
That is normal.
I believe coolant offers anti corrosion. Having just water may change parameters a little but as a temporary fix it should be fine. I would monitor the radiator and other components for leaks otherwise the radiator is likely fine.
 

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Running green coolant in my 2003, Dex eats rubber seals and gaskets. Your issue was due to poor maintenance and running the plain water not the green coolant. A good thermostat will respond quickly and the numbers are on target, the thermostat spec temp is the actual opening point of the element. The prior delay in your temp was a stuck open thermostat, a common issue with these. Can't speak to the condition of the radiator but they're known to crack on the drivers side under the inlet port, motor rocks back on accel and pulls the hose stressing the tank.
 
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