in my 1990 RX7 GTU, the 'add coolant' buzzer keeps going off even when theres tons of coolant in the thing. what could be the problem??

 

Most likely there is still air in the top of the radiator.



Another thing could be the sensor itself is not right. Its the thing right at the top of the radiator. I think it grounds through the anti-freeze somehow.

 

not that this really solves the root of the problem but you can ground out the sensor and it will stop the buzzing a lot of times theyre faulty and for 50 bucks each ill pass....lol

 

had a problem just like that, turns out the rad cap was bad and was not building the proper presure, put a new cap on and the buzzer stopped

 

I don't know if the S5 radiators are like the S4 ones, but my S4 has a bleed screw at the top passenger side of the radiator. I could fill it all day, but if I didn't unscrew that bleed screw to let the last bit of air out, it would always buzz.



Loosen screw, fill, when fluid starts coming out of the bleed hole, screw shut, continue to fill. Works every time.

 

Clean the sensor harness contact and see if that doesn't fix the problem first. Condensation tends to pool right where that sensor sits.



Steve