The car came in with a complaint of a check engine light, but no driveability problems. I scanned a code P0128 and noticed the engine coolant temperature was remaining at 182F. The code will set when the engine coolant temperature hasn't reached normal operating temperature within what the computer decides is reasonable time. In other words, it took too long to warm up. Verified the cooling system was full and used a temperature gun to test the 182F was accurate. Usually this would be a bad thermostat. Often the plastic thermostat housing if broken, but even without that happening the thermostats usually give problems about 100,000 miles and this car was at 109,999. Best move?: Replace the thermostat and then see if the problem is taken care of. The OEM thermostat is a 203F. Always use the OEM recommended temp. Remember that the engine module will be doing calculations based on the thermostat installed being a 203F.
I did lose just a small amount of coolant and topped off the system but this brings to mind something I should mention. Your coolant is a mixture of 50/50 antifreeze and water. You can mix concentrate with distilled water and make your own 50/50 mix but you should use distilled water, not tap water. Usually easiest for you to buy and add is the pre-mixed 50/50. It will be less trouble for you and you'll know you are using distilled water.
The engine coolant warmed properly after the thermostat replacement. I had checked and found an open recall on the car for a software update to prevent cruise control runaway under certain conditions and advised the customer.
Thanks for reading.
Kenny@ggauto.repair
