Hi all, sorry if this will be a bit long winded.

For over a year now I've been having an issue with my radiator fan turning on immediately upon me turning the ignition on (not even starting the car) then remaining on for up to 10 minutes after I shut the car off. I thought it was strange but have been so busy with uni and work that I'd been "solving" the issue by clearing the code with a scanner (P0128 Code: "Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature)). When this summer started I finally had some free time to work on the car and I replaced the coolant temp sensor and bought an Ultragauge. After replacing the sensor and clearing the code once more, I've been driving the car practically everyday and have not had any codes pop up, and the radiator fan isn't staying on after the car is off. However, with the Ultragauge, I've noticed something more disturbing. My car WILL NOT get up to operating temperature. The only scenario it does get up to temp is when I leave it parked and idling for a long time. When driving though, the car practically never gets above 170 degrees Fahrenheit. My immediate assumption is that my thermostat is stuck open and needs to be replaced. I was wondering if anyone else has seen or experienced anything like this before. I'm also wondering if these two issues are connected (I would imagine they have to be). My car still isn't throwing any codes and I've been staying below 4k RPM when I drive it.

Sorry if this issue has come up several times on this forum, I didn't see any issues specifically like mine. If more information is needed Ill try to keep an eye on the thread every day. I'm taking the car back to uni soon and I'm worried for winter.

TLDR: Coolant temp won't get above 170 F. unless I've been idling for an extended period of time (usually takes about 15-20 min (ambient outdoor temps where I live recently have been about 65-90 F). Assuming I need a new thermostat.

 

I agree with you. The thermostat is likely not closing fully.

 

Yeah I'm pretty sure but I figured it wouldn't hurt to hear some other opinions before I buy a replacement. Thanks.

 

Best of luck with the fix.

 

The thermostats on these engines are electronically controlled, and they don’t last forever. Yours sounds like it gave up on life, and will no longer close or control. When they fail, they will fail open. A failed open thermostat will not allow the coolant to get to temperature.

You need a new thermostat.