I have seen many replacement water pumps for this engine. Does anyone have a suggestion as to which is the best? Plastic or metal impeller ect?

 

Scott,

I've moved your question from General Tech Help to XK8/XKR forum. Members here with the same model will be able to help.

Graham

 

All Jaguar OE water pumps have plastic impellers.

The plastic impellers on the very early XK8/XKR water pumps were known to break up but Jaguar revised the spec and this issue has long since disappeared.

There are aftermarket ones available with metal impellers but several members have reported problems with wear on these.

The usual recommendation is to go for a pump with a plastic impeller.

Graham

 

The Jaguar OEM one is probably the "safest" option, and as Graham said, only the very early models had any issue.

I was doing some other work and preemptively changed the water pump on my 4.2L. It looked perfectly fine after 70k miles.

The AC Delco one I replaced it with didn't fare so well. The impeller had a hairline crack which, within a thousand miles, let it slip on the shaft and cause an overheat problem.

I then replaced it with a Beck Arnley metal impeller type, which has gone a few thousand miles without any problems.

 

Besides low quality metal impellers on the market, OAT coolants (recommended coolant for your engine) don't offer good protection against cavitation for the metal impellers.

So long term these will not be safe (don't ask me how many miles), unless you switch to a coolant that also has anti cavitation inhibitors, or check your pump and swap once the impellers are corroded too much.

Metal impeller ones where used on the Ford 3.9 Lincoln engines, but these engines use a hoat type of coolant (with silica which is known to help against cavitation)

Stick with the oem waterpump with plastic impellers, then you are safe long-term.