Sorry for the long post, any advise would be strongly appreciated.

I have a 1999 XJ8 that, aside for the occasional repair, has been running just fine until now.
Doing some searching leads me to believe there might be a problem with the cooling system, high velocity fan, or the thermostat. Although I could be wrong, it seems to make sense.

Here's my problem
>>Shortly after turning the car on, both the left and right hand high-velocity radiator fans turn on and begin whirring loudly. They will run loudly throughout the trip and stay on for several minutes after the car has been turned off.

>>The temperature gauge will rise pretty rapidly from the center position to the highest setting at random times, the needle takes about 3-4 mins to raise all the way up once it starts moving.
From that point until the end of the trip the needle will stay in the "overheat" position, cool down to just above the halfway setting every now and again, then rise back up
Although the temp gauge shows the engine as overheating if you open the hood, while it is (obviously) warm the engine is cool enough to touch comfortable so I think there's no way its actually overheating

>>For the first time today the computer reads out "Low engine coolant" which even though I know I topped it off 2 days ago, could maybe be low, I will double check that after work in about 3 hours once the engine cools down
Only thing to note is that I felt the coolant lid after arriving to work today and it did feel exceptionally hot and like the coolant inside was bubbling a lot.

>>Finally another first time occurrence, while driving on the freeway today the car seemed to get stuck in gears. What I mean is it wouldn't accelerate faster than about 50 and the car was stuck in high rpm's, that and a jerking motion whenever id step hard on the accelorator or the brake made it to be an interesting drive

So any ideas at all? any one with similar issues?
hours of searching leave me to try
changing the thermostat
burping the engine coolant (whatever that means)
having the water pump checked
maybe having the radiator checked


tl;dr
radiator fans stay on continuously, temp gauge reads "overheat" but engine doesnt actually feel hot, and coolant tank feels very hot and like its bubbling.

 

You are going to think this really strange but I would suggest that you have a load test done on the battery and the charging system tested. These cars are very sensitive to voltage issues. The second suggestion is to inspect all high power connections from the battery to the engine bay fuse panels for heat discoloration and tightness.

Once that is out of the way I would replace the temp sensor.

The 'wouldn't accelerate past 50 mph' is probably because you are in 'limp mode'. Given that you should have a Check Engine Light (CEL). Read or have the codes read and get back to us.

. . . and welcome to the forum!

 

I would start with a new thermostat and then remove the water pump and see if the fins are still in there. The early x308's were known for the fins breaking off the impeller.
I would be cautious about over heating you motor.

 

thanks for the welcome and the speedy replies
it seems like things went from bad to worse

somehow the engine coolant was completely empty after I got off work
I checked the nearby area for leaks but none were found
I filled up the engine coolant checked for any apparent problems then set off

>?shortly after (about 15 minutes) the engine appeared to overheat, shortly after that there was a large amount of white steam(?) coming from under the hood

>>upon pulling over and inspecting I found that a hose, specifically the one coming from the right hand side of the radiator into the front of the engine, had burst off and so shot all of the engine coolant throughout the engine compartment which caused all the steam

I was able to fasten the hose back on with a set of pliers, refill the engine coolant, and was able to get safely home pretty much overheated and in "limp mode" the entire time

this seems to change things quite a bit
any new ideas?

 

You have obviously converted from unsubstantiated mystery issues to true coolant system ones.

Change the thermostat, and at least inspect, if not replace, the water pump. You may also be experiencing a leak from one of several common issues but thermostat/pump first. Then do a pressure test on the system and see what leaks.

 

thanks again

test point your probably dead right
after searching on this forum and google Ive found people having the same issue as i am (overheating, high velocity fans, and the hose bursting of the t-stat)being caused by a faulty thermostat
tomorrow afternoon ill be taking the jag into a mechanic to try to get this sorted out


it would make sense though right?
a thermostat sticking either open or closed (im not sure which) could cause the engine to raise in temperature and overheat
this should also explain why the high velocity fans stayed on continuously since the thermostat is faulty (someone else also said the fans staying on happened until they fixed the t-stat)
and finally would the problem with the t-stat and heat combined create enough pressure to burst the hose off

 

Some car thermostats tend to fail by sticking open, these cars seem to do the opposite which is deadly for an aluminum engine.

Indeed, overheating would cause the fans to run more if not continuously and the pressure is certainly enough to blow off a hose connection. Jaguar's spring clamps do not provide a particularly strong connection.

Be careful with overheating as the aluminum engine can be severely damaged. If in doubt a flat bed truck ride is a lot cheaper than a new engine.

 

While you have the thermostat out, put a bucket in front of the housing, start the motor, and rev it; only for a few seconds. If coolant gushes into the bucket, your water pump is ok.

good luck
Pete

 

if youre operating on original equipment I would replace the t stat housing completely, the crossover pipe, and the heater hoses under the intake while the intake is up. All these are plastic and deteriorate with age. I just had a 60k mile 98 XK8 blow the bottom out of the coolant reservoir 2 days ago.(thats a new one)
Pull the water pump unless you know its been changed because those are the problems pumps in that year. stay with a new OEM plastic impellor. DO not be tenpted to go to a metal impellor as the cavties are half the size and flow of the stocker. (at least all the ones Ive seen and replaced)
If your tech is gonna remove the intake to do the hoses youll need a new part load breather hose, the plastic pipe on the drivers side heater hose, the hoses to the throttle body and the heater hose matrix behind the engine. All the plastic will more than likely break when taken apart no matter how carefull you are and these are all items that should be replaced if you go this far. Pop the brass check ball off the t stat to stop coolant surging in the system and trapped air pockets