fitted a new heater control valve tonight
Posted: Tue Apr 02, 2013 9:42 pm
after my split coolant pipe experience, and during the repair process , i confirmed that my interior heater matrix control valve was corroded and non functioning 
this is mounted in the middle of the bulkhead in the engine bay , engine coolant enters via the ( V12 ) coolant rail , then through the valve , in through the matrix , and then exits and goes down onto the the main coolant outlet of the radiator at the front of the engine
this valve is vacuum controlled by the heating ecu , it pulls on a diaphragm which pulls on a lever , and rotates the valve internally,
these often fail , and or become stiff to move,
replacements can be expensive, and mine cost me £55 on the internet ,
fitting is also very fiddly , as there are several pipes and cables in the way as well as the fuel rail in the V12 variant ,
i had already bypassed the original when i had my issues last week , and tonight i went about fitting in the new unit, first , i removed the air balance pipe for the V12 inlet manifolds , then i moved the wiring out of the way , and removed the bypass from the pipework , funnily enough there was little to no water loss, just a gurgling when the pipe was removed, as this is one of the higher points of the engine, and the water must have flowed into the expansion tank.
then i mounted the new unit with two bolts to the bulkhead , offered up the two new pipes , did up the jubilee clips , fitted the vacuum control pipe to the top and then refitted everything i moved out of the way
the whole process took two leisurely hours
hopefully i will now have a working heating system with no leaks........he says.........
BB
this is mounted in the middle of the bulkhead in the engine bay , engine coolant enters via the ( V12 ) coolant rail , then through the valve , in through the matrix , and then exits and goes down onto the the main coolant outlet of the radiator at the front of the engine
this valve is vacuum controlled by the heating ecu , it pulls on a diaphragm which pulls on a lever , and rotates the valve internally,
these often fail , and or become stiff to move,
replacements can be expensive, and mine cost me £55 on the internet ,
fitting is also very fiddly , as there are several pipes and cables in the way as well as the fuel rail in the V12 variant ,
i had already bypassed the original when i had my issues last week , and tonight i went about fitting in the new unit, first , i removed the air balance pipe for the V12 inlet manifolds , then i moved the wiring out of the way , and removed the bypass from the pipework , funnily enough there was little to no water loss, just a gurgling when the pipe was removed, as this is one of the higher points of the engine, and the water must have flowed into the expansion tank.
then i mounted the new unit with two bolts to the bulkhead , offered up the two new pipes , did up the jubilee clips , fitted the vacuum control pipe to the top and then refitted everything i moved out of the way
the whole process took two leisurely hours
hopefully i will now have a working heating system with no leaks........he says.........
BB