Cylinder block coolant drain bolt

[SimonH450P]

With a view to flushing the coolant galleries as best as I can, I tried to remove the block drain bolt, on left of engine below the rear exhaust manifold.

Pretty difficult to undo… should I persist or is this a common break / snap point?

Any advice?? If it doesn’t want to move, can I still effectively flush the block from the thermostat housing opening?

[mike020150]

On engines of this age, any bolt carries a risk of breakage. Common sense is your best guide. A cooling system drain was never meant to be super tight, so if it feels likely to break, leave it alone and spend a little longer flushing the system through other openings. Use a suitable flushing agent to give the system a really good clean but ensure it's flushed thoroughly afterwards to remove all loosened scale and other deposits. Mike.

[JimMann]

Hi Simon, there is a detailed flushing procedure written up for the 4.2 litre engine in the Modern XK Section of the March 2023 magazine edition, if you don't have the hard copy, then you will find the digital copy online here. It should be around page 34.

Jim Mann