Hello again,

The X-Type's engine (2.5 V6, year 2002) overheated after sitting in traffic: the needle would go to the "Too Hot" side, dash lights up in red, but the engine cooling fans wouldn't come on.

I managed to reproduce the issue in a (ventilated) garage, where the car has been idling (and cooling fans would spin on their low speed 4-5 times while keeping the needle at the "OK" middle point -- this most likely happened in traffic as well, I just didn't listen for the fans [had radio on]).

Few minutes later the fans would not kick in anymore, and the needle would then start to creep towards the hot side, bit by bit.

It went all the way to the red, but the fans were never to be heard again (I assume this is when they should kick in at their top speeds)

First thought -- high-speed relay (or similar) is shot; however after plugging in diagnostics, choosing Actuator Test, and running fans on-demand, they were running dutifully at 50% and then at 90% percent when requested (this is what the scanner gave as options).
The thing is, -- I've never heard them spinning faster than 50% when the engine was idling and then consequently overheating.

Does it look to you like the fans ECU is on its way out? Or hopefully you have some more down-to-earth insights (Coolant fluid is on the level, no sludge under oil cap, no loss of coolant anywhere, scanning for faults doesn't bring any up)


Cheers!
Jagsim

 

Jagsim, it could be that you have a trapped air bubble that is not allowing proper coolant flow. Granted, that should affect the car at any speed driven, just not sitting still. Also, the coolant temp sensor is what also tells the ECU if the fans are needed (1 of 2 circuits that will control the fans, other being the A/C system of the car).

From the sounds of things, you have a transistor that is going out on you (common problem) and what happens is when the fan controller is bumped a certain way or takes a good jar, it will cause things to work normally. But, you bump the controller again, it will either cause the fans to loose all power or supply so little that they will barely spin/not spin at all. It can also be a factor of how hot the controller gets as if you do the test with the radiator cold, it may work every time. But, get the radiator up to temp, this can cause the circuit board inside the controller to flex just a little bit, enough to cause it to get into a failed state.

If you are thinking it is the ECU giving you troubles, you can easily figure this out. What you will need to do is to get the fan controller loose from the mount on the radiator. You will then take a paperclip and slide it along the white wire with a purple stripe on it (in the pin #3 spot) and then connect a multimeter to the paperclip and chassis ground. You can then use the A/C to control the fan speed (ie, off and the engine cold, the fans should not move and the multimeter will read around 0 VDC, turn on the A/C to a temperature just below what the outside air temp is, the fans should turn on to a slow speed and the multimeter should read a value around 5 VDC, dial the A/C to "MAX" or lowest temperature that you go to and this will force the fans to run at max speed and the multimeter should read around 10 VDC).

You can play with this a litlte bit using your tool to confirm the above voltages. Then, when things are not running properly, you can take this voltage and see if the ECU is outputting a command to run the fans at max speed but they are only running at a slow speed or if the ECU is telling the fans to run at a slow speed. This should make finding the bad component pretty easy.

 

Many thanks Thermo, apologies for replying only one year later, but better later than later than that!

Soon after your reply, a cold winter had set in the UK, and so the Jaguar behaved well in cold weather without an ability for me to look more closely into the overheating issue..

Later on I had to give the Jag to its owner's relatives, and they had issues with the power steering pump. I haven't heard from them as to how they got on with the car, but they did give her a good care and attention deserved!

I had a lasting impression of this affordable AWD solution, that now got myself an own X-Type 3.0 Estate, which I'm sure I'll thoroughly enjoy starting winter of '18


Many thanks for your answer again, I'm sure many found it useful!
Jagsim