Coolant temperture sensor on 1ZZ-FE 2007 Corolla S

[Eklectic]

Hello all, I was gifted a 2007 Corolla Trim style S, What an excellent automobile! It does have an odd and possible catastrophic point of engine failure. I have ~250K miles on this engine minor maintenance only, 100K and 200K maintenance routines were not performed. The point of failure on mine was the wire from the coolant temperature was rubbed by the engine cover. the driver's side of the cover extends down to cover some unsightly wires and hoses, this extension rubs against the sensor wire as it ascends from the sensor onto the wiring harness and is bent back on itself it is at this point regular engine vibration cause a mechanical open (break) in the wire. The temp gauge unfortunately failed show the normal operating temp. This cause me to run the engine while it was overheating which resulted in a blown head gasket. This wiring problem is an odd failure and I didn't catch it until the gauge finally started fluctuating badly but always from “normal” temp to hot then back down. I replaced the senor, water pump, hoses, thermostat, radiator, fan assembly and belt all these failures I assumed where caused by excessive pressure due to the overheating events. It was after all this this that the gauge finally gave me an indication of a sensor malfunction. During the sensor replacement I noticed the wire and it route. I never like it when a wire is bent back on itself, which I finally check with a multimeter and discovered the open condition. The damage was done however during my test drive after fixing the wire she began expelling white smoke from the exhaust. I torn hr down to find the gasket had failed between the water jacket and cylinder #3. Notes on the Gasket replacement. Check the VVT-i mechanism on your intake cam. Make sure to use FSM procedures when re inserting your chain tensioner. Replace every gasket with quality parts I go with OEM, costs more but I've never regretted it.

 

TL;DR – check the wire from your engine coolant temperature sensor for continuity and beware the temperature gauge may fail good.

 

This would probably effect all 1ZZ-FE engines as they get a bit older 200,000 miles.

 

Thank you, I hope this will help someone if they are having odd overheating issues.