Could it be a faulty thermostate stuck open do you think? When I got home I plugged my OBDII reader in and it wasid the coolant temp was 88C so it wasn't overheating. I will check the wiring today when it gets lighter to see if any of it is fraying. It's done it in th past normally when driving up to Scotland but turnign the car off and leaving it for a bit normally solves the problem but it always returns.

Edit: The wires look OK, I have sprayed some MAF sensor cleaner into the connectors.

 

What temperature should the car be running at? Because after a 10 mile trip at roughly 60mph it reaches about 70C. If I am poodling around country lanes at 30-40mph it can go above 70C and I have seen it at 88C once. Temp outside ranges at the moment between -3 to 10c. Is it possible my thermostat is stuck open?

 

The car should be running at between 90ºC and 104ºC, with it being usually at around 96ºC unless it's under heavy load or very high RPMs. Temperatures above 110ºC should be cause for concern. 115ºC is dangerously close to overheating. The temperatures you're getting do seem a bit low, but I have never driven my XKR in snow or temperatures below 16ºC. I wouldn't know how it should behave in those frigid temperatures you have.

 

It does seem cold to me. I drove maybe 30 miles a couple of days ago and that hit 88C which seems about right but I was driving above the speed limit.

 

Too cold. Mine runs 95-97 deg even in winter. Changing the thermostat is worth a try, but I have seen a lot of variability in thermostats.

 

Cool thanks. Also when I connect my OBDII reader to the car in the morning after I have driven the car the temp reads about 30C. Is that too high or is it possible the car stays warm for that long? I did replace the tempo sensor last year because I thought that was originally the problem. How much coolant should I remove before I replace the thermostat? I don't really want coolant going everywhere.

Edit: ordered a thermostat AJ86484 so I will see if that fixes the problem. I got it from MossEurope as there where some other thermostats available but they didn't look as well made and where suspiciously cheap.

 

Draining the radiator tends to be messy. I slip a plastic hose as far as it will go into the outlet pipe in the bottom of the pressure reservoir and siphon the coolant out.
Have you replaced the thermostat tower with aluminum? This is a good time to do so. I remove the old one by breaking it up with pliers, making it easy to access the rear screws, then replace them with socket heads that can be tightened with a ball end allen wrench.
Another good replacement at this time is the water pipe: AJ85885. The plastic degrades over the years and the radiator hose can pop off. The short bypass hose NCA2213AC should also be replaced.

 

Mine is a 4.2 anyway so it's alrady aluminium. I figure because the thermostat is about the same level as the resevoir there won't be much coolant when you take it out. When I did my coolant sensor barely any coolant came out.

 

To my knowledge there is still no aluminum thermostat tower for the 4.2 engines. The only option is to go with a new OEM plastic one. I last replaced the one on my wife's 2006 XK8 in November 2014. It is officially called the Coolant Outlet Duct, part no. AJ89486 (it comes with a new thermostat). I also replaced the Manifold Front Seal as part of the job (part no. AJ87991) because removing that duct is much easier if you first remove that front manifold plate, and its seal is always pretty baked after a few years of sitting on top of the engine....

 

My car is the R model, the thermostat housing is an all aluminium part. It can be seen here

 

Thanks for the information. Good for the XKR owners for having aluminum there. Sure wish we XK8 owners could say the same....

 

You certainly had us fooled since you quoted the part# for a 4.0 XK8 NA. The SC thermostat is AJ82600. If you had identified the model in your first post we would not have been so confused. Speaking of which, the picture in your last post is a XJR. Do you have a XKR or XJR? This is the XK8/XKR forum.

 

I have an XKR but the XJR is fairly similar. The video is of an XJR because it was the only video I could find of the 4.2 engine with the supercharger. Sorry about the confusion with the thermostat part number. The AJ86484 supersedes all of the other thermostats now and is used on all of the V8 engines I know of. Genuine Thermostat And Water Outlet-v8 Supercharged For Jaguar Xk8 Coupe/convertible 1997 - 2006 Classic | Jaguar Land Rover Classic Parts

 

I installed the new thermostat this morning. I think I have done it correct, the temperature climbs now to about 88C and then levels off I think. I need to take it on a longer trip because I was just driving at about 40-50mph for about 5 minutes driving and about 5-10 minute idleing to start off with. The two upper bolts on the housing where easy to get to but the lower bolt was an utter pain in the bumb. There wasn't enough room to fit a toque wrench in so I had to hack together an allenx key and a couple of sockets. Not much room for my hands either. I didn't drain any coolant first so once I got the pipe apart it pissed coolant everywhere. I topped it back up after loosing maybe 1-2 litres. I knew some would come out but I didn't expect so much. I will let the engine cool down and top up again just to make sure it's OK. I couldn't see any drips but I will keep an eye out for leaks over the next week I think and a very very close eye on my temps.

It was pretty difficult to tighten back up, I don't know if the bottom one is tight enough but it doesn't move. Really not adequate enough room unless you have a really low profile socket wrench.

 

Did you back off the big allen head on top of the intercooler to bleed that?

 

No was I meant to? Should I just undo that and then tighten it back up? I was under the impression the car could self bleed? I will do that now, thanks. I can't do it, I don't have anything that fits such a large allen key. Is it that important? What size is it anyway, I may need to go to a shop to buy one.

 

its a 19mm hex head, what I call an allen head . Many people make a tool out of a bolt that has two nuts tightened against each other (for the turning). I just bought an inexpensive allen head set from Amazon that I needed anyway.

yes, the system is suppose to be self bleeding.

But since you have to loosen the top hex head to make the bleeding process go faster why not take the plug all the way off and top off the system there as well as at the overflow tank ?

Z

 

Understood. I was looking around for the correct size, some people say it's 15mm, others 12mm. You said it was a 19mm. I may need to pull out a tape measure and measure mine. Knowing Jaguar they used different ones depending on the year as a joke. Is it necassery to perform the fast bleed or will it do it itself eventually with no damage? Thanks for the help in advance.

 

mine is an ‘02 XKR, if that helps

 

My plug looks a bit different. I think this is like how my thermostat housing bolts where hex bits not socket bits. I think I will measure mine when it's light outside tomorrow.

I measured mine, it's 19mm I think.