Hello, I have a '97 XK8 coupe I purchased cheap with what I assumed was a blown head gasket due to the milky oil. However, other than the milky oil it doesn't have any of the tell-tale signs like white smoke out of the tail pipe or engine overheating issues (granted due to the oil I haven't let it run that long).

I still need to run some compression and leak-down checks on the cylinders, but I read on the forums that a bad oil cooler might also cause the milky oil symptoms.

Did the XK8 come with an oil cooler or only the XKR? (fingers crossed it did and that's the issue).

Thanks.

 

As far as I know, the XK oil cooler is an oil to air cooler and not oil to water as is the gearbox cooler. So it can only go bad in terms of an internal blockage or an external leak and neither will result in milky oil. The milkiness may be a result of lack of use and may go away but until you have done a compression test and tested the coolant for products of combustion you cant be sure.

 

Thanks for the clarification on the oil cooler being oil-air and not oil-water. A quick Google image search of the cooler itself confirms.

I guess we'll see how the compression test goes, but other than a head gasket or crack in the block water jacket I'm not aware of any other way coolant can mix with the crankcase oil.

 

Your xk8 doesn't have a oil cooler. The lines running to the radiator are for the transmission.

 

A shot in the dark, but doesn't that year have a problem with the dipstick markings which resulted in owners adding too much oil to the crankcase causing 'whipped frothy oil'? The later models have a metal 'guard plate' of such inside the engine to prevent the oil from being whipped and 'frothing', however, I do not think the earlier AJ28 motor has this plate.

If the updated dipstick with the correct oil fill level has not been installed, or the original dipstick has not been re-marked with the correct oil fill level, then there could be too much oil in the crankcase, being 'whipped' and causing the 'milky' oil appearance. If this is the case than it is an easy fix and there are instructions in the STICKY DIY section on how to correct this.

 

All engines had the windage tray. The early AJ26 dipstick left room for an additional quart, and I always ran mine that way with no frothing.

If the oil is milky I think you can expect to find a failed head gasket, which might even be evident when comparing spark plugs.

Carefully inspect the cylinder liners as the nikasil coating is damaged by overheating, and the temp. gauge may not go toward the red zone until the engine reaches 235 F.