I have only owned my XK8 for a few weeks and am getting to know it, and starting to see some of the problems that will need sorting. One of these is that the cooling fans run at high speed all the time.

When I start the car, the fans start after around 8 seconds at slow speed, then a few seconds later they are running at full speed. The engine is cold, the air con is off so I don't see any reason the fans would be running.

I did consider the possibility that the car has previously had cooling issues and some clever sod has "fixed" that by forcing the fans on, but I cannot see any obvious wiring mods and everything seems very well behaved temperature wise apart from the fans running when they shouldn't.

Anything I may have missed before I start investigating the ECU/fan controller?

 

Hi,
Try pulling the connector to the refrigerant 4-way pressure switch off to see if that makes any difference. The switch is on the aluminium pipe that runs across the bottom rear of the radiator.

What are the last 6 characters of your VIN?

 

I have seen that switch, I'll look at that tomorrow. I have read that air con fluid low can cause the fans to run, but I discounted it as even with the A/C turned off, the fans run. I will pull the connector and check though

A29467

 

OK so definitely a 4.0L. Just checking as there's a 2002-registered car in the island that is a 4.2L which caught me out. The cooling fans work rather differently on those.

Other possibilities are the fan control module here:
https://www.jaguarforums.com/forum/x...8/#post2568716

...although that wouldn't explain the time delays, or the ECM thinks the car is running hot.

 

Is there any change with engine temp sensor unplugged?

 

I pulled the plug from the pressure switch. Lots of green copper blood inside!

Started the car and the fans did not start, so it looks a lot like the pressure switch is the issue.