The cooling fan on my Xjr has become very loud. Have never heard it so loud before. What can be the cause of this ?

 

Have you checked your mounting points...to include the fan motor itself? A grommet may have eroded away?

 

Just to eliminate the possibility that what you are hearing is the normal sound of the radiator fans (2 of them) when they are at High Speed. Up to certain engine temperature, the fans run at Low Speed (rather quiet) and are switched to High Speed (fairly noisy) if the engine temp goes higher. This is controlled by a special (long) fan relay located low down at the front LH corner of the engine compartment.

When a cold engine is started (AC off), the fans should initially not run at all. When the engine reaches 90C, the fans are switched on to Low Speed. At 97.5C, they are switched to High Speed. Do a test with starting the engine from cold (AC off) and let us know how the fans operate.