Hello, I’m Dylan. My 2008 Ford F150 XLT 4.6L v8 check engine light appeared one morning. OBDII P0128 Coolant temp below thermostat regulating temp. This makes sense because the engine isn’t overheating, in fact, it appears to be operating at the right temp. I’ve had this truck side about 6 years. The mileage was about 117k when I purchased it and it’s now at 179k. I change the oil every 3k and I’ve had the transmission fluid changed twice. She has never overheated and the only time the check engine light came on other than this situation was a code to replace the EVAP cannister. I drive a lot of miles because I work in another state. Lately it’s been about 80-100 miles a day. Mostly highway miles. So I’m sure the engine isnt overheating. I wanted to ask when I change the thermostat, should also flush and/or change the coolant? Also, would idling the truck for longer than 5 mins often cause issues like this or with the emissions system? Thank you for your time and sharing your knowledge and wisdom on your YouTube channel is very helpful and informative.
should also flush and/or change the coolant?
yeah it should have been done a few times already. 5 years is what it says on the bottle I think.
when I change the thermostat
I would make sure the coolant temp sensor is working properly.
it appears to be operating at the right temp.
How do you know? According to the gauge you mean? Well if the gauge is correct, then the thermostat is probably fine right?
would idling the truck for longer than 5 mins often cause issues like this or with the emissions system?
No
