2003 Hyundai Sonata Car overheats in stop&go traffic &a

SASSYCAT

MEMBER
2003 HYUNDAI SONATA
6 CYL
FWD
AUTOMATIC
89,000 MILES

We replaced the engine in my car with a used 2005 Sonata engine. We were told by the dealership it was the same engine and not a problem. After my husband and my brother put the 2005 engine into the car, it's been running warm in stop and go traffic and with actually go into the red when I'm pulling a very steep grade. I drive through mountains everyday to work and it doesn't do it all the time, just when I'm really pushing the engine, like if I have to pass someone on a grade. We've replaced the thermostat, had the radiator checked, and had the fans checked. There was an issue with the fans but they were fixed and the problem disappeared for a while and then came back. The mechanic insists that the fans are working properly now and that isn't the problem. We've replaced the temperature sensor in the engine as well. Nothing has worked and we were told by the dealership that it is an imcompatability between the 2005 engine and the 2003 computer. Any thoughts on this?

3 Replies

JACOBANDNICKOLAS

MECHANIC
108,289 POSTS

First, I would be really upset with the dealer if first they told you it would work, and now they are telling you that it won't work. Here is what I suggest. Considering you have already replaced the t-stat, flushed the radiator, and repaired the fans, I would check the fans myself. Start the car and let it idle. Once the temp starts to raise above normal, the fan should kick on. If it doesn't, it's not working correctly. Next, when you replaced the engine, did you switch the sensors from the old engine to the new one? If so and there was a place for all of them, the computer should be reading the same information from the old ones. Finally, and you may not like this one, check the engine's compression. If you have a bad head gasket, it will cause the engine to overheat.

Let me know what you find.
Joe

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Friday, August 21st, 2009 AT 11:37 PM

SASSYCAT

MEMBER
2 POSTS

The thing is the fans do come on. I can feel the pull on the engine when I'm at a stop light when they come on, but the needle will stay high and come down a little then the fans turn off while the temperature is still high. It doesn't seem like they stay on long enough or do enough while they are on. It used to be that I could hear them very loudly when I pulled into the garage, but now when I park the car, I hear them but not as loud as they were before. Do they run at variable speeds? Maybe they aren't running at a high enough speed?

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Saturday, August 22nd, 2009 AT 1:07 PM

JACOBANDNICKOLAS

MECHANIC
108,289 POSTS

Was the temp sensor from the new engine switched with the original one? If you still have the sensor from the newer engine, that could be the problem.

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Saturday, August 22nd, 2009 AT 4:28 PM