My 10 year ford headache

Im trying to work out a car issue. Its a 2010 ford fusion 2.5l its hard starting at what seems to be random and the temp gauge reads under the cold line even if ive been driving for hours. During the winter it would barely start sometimes on -25° it just wouldnt even turn over. Ive done the o2, fuel pump, spark plugs, injectors and the purge canister thingy. Ive taken a look at the cht sensor and it probably needs replacing along with the connector as there is significant corrosion and damage. Unplugging the sensor doesnt fix the problem though.
Helllp! I dont want to keep throwing parts at it. Othet than this issue it runs really great and dives quite nice. Not ready to give it up.

It sounds like the thermostat is stuck open.


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Pull the thermostat, put it in a clear glass, and pour boiling water over it. Does it open? If so, it works. This means you have to drain the coolant. If it hasn’t been replaced, it’s a good time to do that too.

If you remove the thermostat, and find it’s stuck open or broken,


There would be no need to test it.



You have done plugs and injectors and have cold motor and had no idea it could be thermostat? You know what regulates coolant temp?

Just replace the thermostat and get it over with

If you’re going to take it out, you replace eit

No ifs ands or buts

Don’t waste time trying to test it . . . no offense to anybody

Report back to us afterwards, please


Agreed on the thermostat. On the hard starting it sounds like you spent a small fortune on unneeded parts.

Not wanting to turn over could be the battery, worn starter motor, or possibly a faulty range selector switch. Another possibility could be a flaky starter interlock relay and which I assume the car has a security system built in. At 25 below anything can happen.

Battery test and an amperage draw test on the starter motor might be a good idea. And no, the starter does not have to be removed to do this test. It can be done with an inductive ammeter.

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Is your radiator full, not the recovery tank? if the level in your radiator drops below the temp sensor, your gauge will always read cold. Those sensors are meant to read liquid, npt air.

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