My wife has an 2002 XK8, I when I returned home from a trip. She told me that the electric fans came on after a short drive in 60 degree (F) weather. I looked to see that the coolant was a bit low in the expansion tank. After topping off the coolant, I then noticed some coolant at the base of where the coolant enters the block (see the attached photos). It is a vertical piece that has a round cap with a HEX fitting in the top. In the case of this particular non-supercharged 4.0 V-8, what would be the symptoms if the thermostat was not opening?

Thank you in advance.

Jamie

 

After reviewing the photos on the post, I wanted to add that the coolant is sitting at the base of the black plastic piece, just below where the wiring is is plugged in. It is difficult to see the small pool of coolant, but you can see what appears to be dried coolant on the plastic piece.

Any help would be greatly appreciated!

Jamie

 

That's the thermostat housing, a common failure. Buy an aluminum one from one of the sponsors and locate the diy in the sticky. The overheating was probably due to the thermostat sticking, so make sure a new one is included.

Most of us would suggest replacing the black plastic crossover pipe, upper and lower radiator hoses and the short hose between the pipe and the housing. Some would also say include the water pump and serpentine belt. Where does one stop?

 

Jamie, if thermostat was not opening she'd overheat since it would prevent circulation to the radiator for heat exchange.

Fyi fan goes on each time a.c. is on.

Your temp gauge is nearly useless. Will only register cold engine, warm engine and overheating has started. Look up realguage when you have time.

Did you know that an OBDII tool will display coolant temperature? Not sure if you have one or not. You can drive with it connected to monitor things.

Say more please about how we can help.

John

 

As RJ237 indicated the plastic thermostat housing is a often source of coolant leaks. He didn't mention that you were going to learn a few new terms like 'bent wrench'. The rear bolts at the base of the housing are effectively inaccessible without a special tool. Search the forum for more than enough information to make this a relatively easy job.

I strongly urge you to replace the plastic housing with the aluminum version as it is less expensive and an one time effort. Paint the bright aluminum black to match the all black engine or it will end up a shiny beacon until it corrodes into an unattractive dark grey color.

All your hoses are now 15 years old and you certainly wouldn't drive on 15 year old tires. Not a bad job except for the bottom left clamp.

 

Echoing what's already been said, this might be a good opportunity to address all the usual suspects 'while you're in there' and include the valley hoses.
The crossover pipe is made of the same plastic as the thermo tower and ages just as badly. Sadly nobody as yet has copied it in aluminium.

Nothing to be scared of here, but note that the lower radiator hose has a slightly larger bore on the radiator end (where the awkward clip is). It's possible to get this on upside down

Forum sponsor SNG Barratt can oblige with the ali tower, and most probably everything else.

 

If you have not already done so, I urge you to install a "RealGauge". Simple to do and a quality addition to keep your XK8 safe.

 

Thank you all for your thoughtful replies. All of you confirmed what I was expecting that is the thermostat and aging plastic pieces causing the problems. As I typically do most of the DIY items on her car. Time does not allow and her planned trip to go out of town yesterday afternoon forced my hand. Triple A picked up the car and took it to the Jaguar dealer. I know, how most of us feel about the dealership. In our case, the long time Jaguar dealer was purchased by Hendrick and I have had a great experience with Hendrick in the past. Plus, the wife headed out of town in a newer Jaguar sedan. Luckily for me, she would prefer her car over the newer sedan.

As mentioned, all of the hoses and the belt were suppose to have been replaced within the last four years. I will have them check those and the crossover plastic piece. You guys have given a wealth of knowledge and my call to the service department should go smoothly.

Thanks again for the responses to my destress call and for the suggestions.

BTW...I am not sure if I would have tackles this one myself. That bolt requiring the bent wrench would have caused me to break out a big hammer. And, dealing with flushing the air out of a cooling system is not one of my favorite things to do.

Again, Thank you all!

Jamie

 

Your big hammer comment is not far out. I use vise grips to break up the old one, then socket head screws and a ball drive to replace. I hope the dealership has someone familiar with the XK8.

 

+1 on Hendrick's. I try to avoid dealerships, but I must say that Hendrick's has done my family right.