Dave, your LS doesn't have a conventional Engine Coolant Temperature sensor. It has a CHT (Cylinder Head Temperature) sensor that threads into the left head between #5 and 6 cylinders. It's in the engine "valley" and can only be accessed by removing the upper and lower intake sections, which is a good 4-5 hour job.
That being said, I have NEVER needed to replace a CHT in an LS, nor has anyone else I've spoken to. They just don't go bad.
It would be really nice if you could post the codes you received. I suspect they were probably P0125 or P0128, both derivatives of the same malfunction:
"P0125 - Insufficient Coolant Temperature For Closed Loop Fuel Control
P0128 - Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
-Indicates the ECT or CHT sensor has not achieved the required temperature level to enter closed loop operating conditions within a specified amount of time after starting the engine.
Possible Causes:
Low engine coolant level
Leaking or stuck open thermostat "
You most likely need a thermostat. (There's a small chance you may have a wiring problem, but I doubt it).
Can you change it yourself? Sure, but I advise against it.
Replacing the part isn't the problem; that's relatively straightforward. Filling the cooling system after is the nightmare.
First, you can only use Premium Gold coolant. Check out Ford's warnings:
"TO MAINTAIN THE INTEGRITY OF THE COOLANT AND COOLING SYSTEM,
Add only Motorcraft Premium Gold Engine Coolant VC-7-A (in California and Oregon VC-7-B, in Canada, VC-7-C) or equivalent meeting Ford specification WSS-M97B51-A1 (yellow color). Use the same coolant that was drained from the cooling system. Do not mix coolant types.
Do not add Motorcraft Speciality Orange Engine Coolant VC-2 meeting Ford specification WSS-M97B44-D (orange color). Mixing coolants can degrade the coolant's corrosion protection.
Do not add alcohol, methanol, brine or any engine coolants mixed with alcohol or methanol antifreeze. These can cause engine damage from overheating or freezing.
Ford Motor Company does NOT recommend the use of recycled engine coolant in vehicles originally equipped with Motorcraft Premium Gold Engine Coolant since a Ford-approved recycling process is not yet available."
Secondly, getting all the air out of an LS cooling system without some type of vacuum assisted evacuate/fill machine is virtually impossible.
Yes, there's a procedure for manually filling and bleeding the system that involves using the engine block fill port and opening and closing the heater bleed valve under the driver's side of the wiper cowl, but it's a 19 step (yes, 19 step) process in the shop manual. It takes ages and usually doesn't get all the air out.
Post the codes, if you can, and let us know what happens.
