I have an 07 XK. Today, for the first time, the engine fan has run for about 5 minutes after shutdown. I didn't get any warnings but it was after a short 4 mile drive.

Sounds like a thermostat but would appreciate advice.

 

Under hot operating conditions the fans will continue to operate after the engine has been shut off. Once coolant temperature is reduced they will shut off.
Check coolant level.

If she is running fine, I'd look at the thermostat as you concluded.

If the car is hesitating to start at all or a rough start , I would look at the ECT (Engine temp sensor) as this sensor allows to richen the mixture at lower block temps.

Regards,
D.Fricke

 

How hot was the ambient temperature? I have found that during very high temps the engine fan will stay on for several minutes after a shut down if the car has been in heavy slow moving traffic during very high temps.

 

The ambient was about 85 which isn't hot for Arizona. Using Torque Pro, I checked coolant temp and it peaked at 205, which is the correct temp for the thermostat to open.

I did have TSB00046 done last week which resolves a low speed engine ping issue. The dealer said that TSB's sometimes include other changes and thinks that's probably what's causing the fan to run. It stays on for < 5 minutes. But, it didn't start doing this until a couple days after the TSB was applied.

I haven't found any leaks and the coolant level is OK.

According to the schematics, the ECM controls the fan operation so something is telling it that the car is hot, even when the temp is 205.

 

Shortly after buying my car used a tad over three years ago, I noticed that the fan ran for a prolonged period and that the right front fender and the right side of the hood were so hot after shutdown that I couldn't touch them for more than a few seconds.

Took the car to the dealer and the "seasoned" SA and dealer mechanic said that was absolutely normal. "These cars run so hot you can fry an egg on them."
Bull shiitake mushroom.

Bye bye Hennessy. Found an indie to replace the thermostat and plastic thermostat housing (a known weak point.)

To your original point...the fan still runs after shutdown when it wants to. Sometimes for a few seconds, sometimes for a few minutes and sometimes not at all. Assuming you have no other coolant issues I do believe your situation is normal.

Best regards,

 

Maybe this is what they are talking about:

Issue:
After completing technical bulletin JTB00268, some customers have reported that the engine fan is running after the engine has been switched off.

Cause:
JTB00268 updates the engine control module with revised software. The software lowers the engine temperature by running the fan for a longer period of time after switching off the engine.

Action:
After completing JTB00268 please explain to the customer that the engine fan may run for a longer period of time than they would normally experience, and this is as a result of the software download.

This is expected and is normal. The fan will stop running after a short period of time.

 

At the age of your car, it is good preventative maintenance to flush the coolant and replace the thermostat and plastic thermostat housing.

Thermostats can intermittently stick, as the plastic housing has a known track record or deteriorating causing leaks and improper routing of coolant due to internal deflector breakage.

 

Appreciate the advice. I'm watching the temp using Torque Pro (where's the temp gauge on these cars!) and now assuming the TSB patch must have initiated the fan.

But, what's with a plastic thermostat housing? I will change it and the thermostat to be safe. I'm taking a road trip in a few months and don't need any cooling system issues.

 

The thermostat seal can sometimes fail causing the PCM to receive a signal that the correct operating temperature has not been reached within a certain time, or that the mixture is incorrect when the engine is cold. If either of these situations occur, the MIL will come on. They can be corrected by replacing the water outlet pipe assembly, which contains a new thermostat and seal.

Over time the plastic water outlet can begin to crack causing coolant loss or overheating, so it is best to replace the assembly once the vehicle requires a coolant change.

 

It looks like there are 2 parts involved besides the thermostat. There's a thermostat housing and a water outlet. Are you recommending changing just the thermostat and thermostat housing, or also the water outlet. The outlet is more expensive and a bigger job to install, but also plastic.

 

The water outlet comes with a new thermostat and seal already included. The part number is AJ811793 and includes the water outlet, thermostat, thermostat seal and water temperature sensor. It also includes the water outlet seals and Torx fasteners.

The replacement water outlet is also made from plastic, but will provide service until the next coolant change is required.