i noticed my temps are around 190 on the highway, but stay at 180 around town and below 50 mph. i replaced the water pump with a cheapish one last spring, and it was ok until about mid september when this started. highway with a/c on and about 70* ambient, it stayed around 195 until i slowed. now its 20 degrees out and is staying around 190. new radiator, new thermostat, all plastic peices are in place and no debri blocking airflow. i do have rust issues with the coolant and i have been having to flush it out every 10k miles. made the mistake of running straight water for about 2 months. i always use prestone 50/50.

 

190-200 is optimum operating temp...

 

That is around standard operating temperatures for newer vehicles.

 

That's what I said :P




If it helps, mine does the same thing. new thermostat, flushed cooling system quite a few times... before the flush it would ran way to hot(210-240) after the flush it wouldn't get over 140-160, after new thermostat it runs 185-190 in town, 190-200 on highway. which is good, anything 180 or less you will start loosing some of you fuel milage from my understanding.

 

It shouldn't vary at all... To me, this indicates that there is still air in the system.

The thermostat should control the temperature to ~195*F at the t-stat which translates out to around ~205*F at the coolant temperature sending unit. This is regardless of operating conditions unless things are very hot out which may cause it to run warmer than that as the system saturates, in terms of temperature.

 

its got a 180 thermostat, and stayed at 180 all the time during the summer while moving, but moved up in traffic as expected. its was fine for the whole summer, but started doing that late summer. in fact, when it was 112 degrees this summer, with the a/c cranked full, it only got to 205 on the highway, and about 215 stopped. im thinking the water pump, being not the best quality, has developed excessive impeller to housing clearence. ive seen it before where a new pump has caused overheating by that. but i wouldnt expect it with it only have 20k put on the pump in the last year.

ive also tried flushing out rust and corrosion but it seems like i can never get it all out. ive back flushed the block with a garden hose through the t-stat, and through the water pump, until it came out clear. but even after that i still get rust deposits

 

I would not expect that from such a recently installed water pump either. If you are still getting rusty deposits from flushing, my guess is your radiator is partially plugged. That would definitely cause your temp fluctuations.

 

ill see how it goes come spring time. i might just get a better rad and a high flow pump possibly. i dont have any coolant loss, so im not expecting a head gasket issue quite yet

 

Check your clucth fan out. If you don't hear roar when it is suppose to kick in, thats the ticket. I bought a heavy duty one from auto zone about 2 yrs ago with a Life Time Warranty (Thank God) for it lasted a little over a yr. I live in AZ so the temps are high out here in the summer time, with them reaching 115 on a good day. I was taking my wife to the airport and notice the temp gage getting hotter and hotter and by the time I got to the airport it was at 245. I started to sweat bullets for its about 45 miles back home and it was 110 that day. After dropping her off I pull over at the 1st place I could from the airport and lift the hood and things were starting to melt. So I relieve the pressure and let if cool down a little. Then cut the A/C off, lower all windows, turn the heat on high and took to home. That kept it around 210. The same day I took the Fan Clucth off and return it auto zone and pick up another for free..So far so good..but they should last at least around 7-8 yrs from what I have heard. So give that a check.

 

Changing the fan solved a problem with the car overheating when moving? Usually the fan only affects the temp when stopped or bumper to bumper traffic. I lived in Yuma for 7 years so I know all about the heat...now I have humidity which I'll take over 115 any day.