4.2L V8 XK owners: Have you noticed much fluid turbulence in the coolant reservoir, when the engine is cold and at idle speed? The fluid in my XK's coolant reservoir shows very little movement.

Nigel Thorley in the 2015 edition of "Jaguar XK/XKR" asserts on the top of p. 111 that the fluid will "circulate quite briskly" for the prior generation XK, while discussing the concern that the coolant pump plastic impeller may disintegrate over time. Lack of such circulation is thus an indicator that the pump impeller has failed.

I am wondering whether this observation is valid for the X150 4.2L model as well. Thanks!

 

Low volume, high flow indeed. That's why it warms up quickly. The reservoir is actually a degas bottle. It's baffled by design to help separate air bubbles from the coolant. It draws off the top of the cooling system through the little hose and feeds the heater core from the bottom. Very little coolant actually flows through it. That's why it doesn't look like there's much flow.

 

I agree with this finding for X150, which is contrary to Nigel Thorley's observation regarding the X100 model.

 

I always thought he'd 'cut & paste' this observation from another of his texts on earlier models. My X100's never showed much fluid movement in the Expansion Tank and neither do the X150's.

Graham