whats the other sensor on the back of my s4 13bt water pump housing? I have the green rectangle one, then about 2inches to the right, theres an octagon with two wires coming out of it that go into a plug. My buddies s5 TII housing does not have it. I haven't been able to find it in the FSM, anyone have an idea of what it is? The wires broke out of it thats why I'm asking, so it's not hooked up right now.

 

S4 water pumps should only have one sensor on the back (the ECU's coolant thermosensor) and the S5 water pump should have two (the thermosensor plus the auxiliary e-fan's temp switch).

 

it's a jdm engine, I don't know if you knew that. But it does have the two sensors on it. Maybe it's a late 88' engine?!? It prob don't matter cause I found some oil in my radiator so I think the engine I got was fucked.

 

I believe you only need the green plug. I installed a aftermarket water temp gauge in the other on my last FC.

 

JDM makes no difference. It's possible someone has fitted an s5 water pump housing. Does it have a plastic or aluminium neck on top of the water pump?

My late-88 FC is ex-Japan, and only has one sensor. I'm betting your mate's S5 doesn't have the auxiliary e-fan, so it won't have the temp switch.