Just found this on XPower
Re: 120+ 1.8 Engine Help Needed - URGENT!
There are 2 sensors on an alloy elbow casting on the left of the engine block towards the radiator (remember left and right is as though you are in the drivers seat)
The lower sensor is the one that sends a signal to the coolant gauge the one to the side is the one that controls the fan/feed to the ECU.
removing the sensor will cause coolant to leak. Once the replacement is fitted, remember to use Loctite 557 on the threads, you will need to bleed the system.
Do not remove the elbow or you will have to replace the gasket.
Bleed screw is a small nut in the main coolant pipe just between the batery and the throttle body area, it might be hard to locate with the wiring loom in the way. careful not to cross thread this or you will be buying a new pipe!
To Bleed,
ensure the heater is to max heat
mix coolant and water concentration in a suitable container, do not add neat coolant!!
Top up resevoir to max level, refit cap.
Start engine and let it warm up until the fan has cut in once, do not rev, let this warm up on tick over.
Ensure the heater is pumping out hot air.
Turn off engine, release bleed screw and let air out until coolant flows and no air. The screw doesn't need to come out fully and it may be under a considerable pressure so be careful! Don't loose it either.
Caution, coolant will be very hot!!!
Carefully remove expansion cap on resevoir, put a rag over the cap to stop pressurised spray. If it gurgles madly and the resevoir starts to over flow then there is still air trapped in the system.
Top up to correct level and repeat process until no more air escapes from bleed screw and the coolant cap can be removed with the water errupting out!
Do not remove bleed screw with engine running, water pump pressure can blow it out plus spray you in face with scalding hot coolant.
If the heater doesn't get hot then there is an air lock in the heater circuit (a pig for doing it on the R45/ZS)
Gentle squeezzing of pipes helps to move trapped air.
Bleeding a K series engine is critical, they have a small coolant capacity and being alloy heat up really quick, this can be critical on head gaskets so do it properly and don't wreck your engine!
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