Hello there,
I hope you all are doing well.

I’ve just bought a used Toyota Camry 2007 (V4_2.4L) and I noticed that while I am driving the temp gauge starts going down, giving an indication of the engine not being fixed in the correct operating temperature and once I stop, the temp gauge starts going up and reaches the correct operating temperature (a bit lower than the middle).

I assumed that it would be due to a faulty thermostat that stays open and does not let the engine to stay warm while driving, then I replaced the thermostat but it didn’t help and the problem still persists.

I am writing to ask if any of you have encountered the same problem and may provide me with probable fixes for it.

Thanks

 

Was the engine ever over heated?

Is the coolant disappearing from the reservoir?

Are the coolant fans operating as designed?

 

I don't know if it has ever been ocer-heated before as I 've just bought it.

The coolant is not disappearing and the water level is always OK.

The coolant fan starts to spin when the temp gauge reaches a little lower than the middle for a few seconds and then stops as the temp gets ok.

I tried to replace the Coolant temperature sensor but the problem still persists.

 

Tough to make a pinpoint diagnoses.

Suggest starting by confirming the coolant temp is actually varying. An ODBII scanner that reads out coolant temp will confirm this. The cars computer/OBDII uses a separate coolant sensor to read coolant temp.

Feel the foam (heat shield) under the intake manifold head shield material for moisture. This engine has a problem with failing engine block head bolt threads that pull out. There is a lot of info on this on the internet. External signs of a problem can be damp foam and or a dropping coolant level in the reservoir tank. Could be the head gasket failure is currently negligible.

A "block test" can check for a failing head gasket by detecting exhaust gases in the coolant. Exhaust bubbles in the coolant will trick out the coolant sensor.

It can happen the water pump impeller blades start to deteriorate or the impeller even fall off the drive shaft.

Plugged radiator. Check coolant temps for inlet and outlet lines by feel. The past owner could have tried to clean the coolant system with cleaner and here just plugged up the radiator. Don't use coolant system cleaners.

Hows the transmission? Any slipping as in the engine RPM increases but the MPH does so at a slower rate.