Thermoswitch in the filler neck?
 

I just purchased a used japanese engine and found out when it arrived that it came off a 96-98 FD. Alot of changes in this engine; black box, oil metering pump,some relocated parts, etc. It's not the efini turbos though of course(99-up).Anyways this engine also doesnt have a thermoswitch behind the water pump housing maybe because the 16bit ecu took over this function?not sure. Well I need to put one since im running the 93-95 U.S version harness and ECU(power fc).I just finished the hybrid of the Jap and US harness and my car is currently running fine, I just wanted to know that my engine is good for now but I still have a wire that needs to go to a thermoswitch, my question is could I still get an accurate temp reading if i installed it by one of the factory ports in the filler neck?I know it's not a good idea for a water temp gauge in case the thermostat was stuck closed but does it matter for the thermoswitch since all it does is turn on the fan at a certain temp so if the thermostat was stuck closed anyway theres no way of it flowing the cooled coolant to the engine. I just want to know if I can get an accurate reading at the filler neck for the thermoswitch if i want it to turn on at the specified temp like it's supposed to, im also using the FC thermoswitch. Thanks for any advice.

The stock 93-95 thermoswitch is mounted in the filler neck. So I see no reason why it's not acceptable.

Is there any reason you can't install a 93-95 filler neck in the engine? It almost seems easier/safer.

Dave

No its not in the filler neck, it's behind the water pump housing assembly (very hidden). theres nothing installed in the filler neck holes but factory plugs(allen heads). Are you sure you know what a thermoswitch is? your not looking at the coolant level sensor are you?
The reason for this topic is because of the thermostat location, thermoswitch is normally on the wax side of the thermostat meaning it's always sensing engine block temparature.

Wheres the real FD gurus?

Yep, I know exactly where the thermoswitch is, right behind the filler neck. But you're right, it's not in the filler neck casting. The neck bolts to the pump housing which bolts to the front housing, all within a few inches of each other.

In any case, in the worst case you could install the t/s in the coolant hose that leaves the engine block from the rear housing to the throttle body, or some other engine-side location.

Dave

I wanted to install it there like where you said ( hose to throtlle body) but Im most likely gona use a temp gauge there already, it's just alot for one hose but if i have to than i will. Do you know whats the best fitting to use inline with this size hose?