I have been saved from a serious problem by the RealGauge, which is a relief! I am, though, overheating my 4.2xkr, and this is the relevant information:
Temperatures are measured with an obd reader

1. Normal running temperature is between 99 and 102 degrees celcius, occasionally flipping up to 103
2. With a spot of acceleration the temperature climbs a bit, but then will fall back on gentle cruising.
3. Fans were both running fast when I checked the engine, having stopped at 102 degrees.
4. Fans slowed to a halt when the engine was stopped, and were checked. Both are complete and unbroken.
5. The thermostat has been replaced, and the system appears to be full of water, with no leaks.

All of that seems ok to me. However, quite rapidly under what is euphemistically called ´spirited driving´ the temperature climbs rapidly to 110 degrees, at which point the RealGauge shouts at me. If I now put on the heater fan (which in the current 35 degree C temperatures is not an awful lot of fun) the water temperature falls back to my normal 100 to 102

Any suggestions where I should be looking? Radiator? And is there any way to check the water pump on the vehicle - it is not making any unhappy noises. Thanks!!

Conversions:
100C = 212F
102C = 216F
110C = 230F
35C = 95F

 

Check the intercooler pump under the air filter. You should hear it running with the ignition on.

 

Thanks for this suggestion. There is a humming whirr with ignition on, which ceases about half a second after ignition off. I assume that this is the pump hence the problem appears to lie elsewhere.

 

That would not be the pump but more likely the ECU Fan shutting down along with the plethora of clicks and whirs associated with the key in off position after running the engine or switching the key to position 2; with the key in position 2 the pump will run continuously as will the ECU Fan regardless if the engine is running or not. The IC pump is located beneath the Intake Air Filter Box, slight pressure on one of the IC hoses with the key in position 2 and you should feel coolant flowing, and with your head above the Filter Box you should be able to hear the pump running. My pump just failed at 61,000 miles and popped the Fuse so make sure to check the 15 Amp fuse for the pump in the Passenger Side Fuse Box within the Bulkhead, I forget which one, just look up a Fuse layout chart.

 

You are running about 10`C hotter than on my 4.0 XKR. You changed the thermostat, but did you also change the coolant and bleed the air from the system. The thermostat also has to go in the right way up. The other thing worth checking is that the temperature reported by the temp sensor is in fact correct.

 

Thanks dibbit and 03XKR. To answer your points - changed the thermostat withe the hole at the top, I did not change the coolant but refilled and burped the system ( not a huge amount of water was lost when I removed the thermostat cover). The temperature was measured with and OBDI reader.

Now there is further information. I turned on the ignition and a pump or two started. Definitely no water pumped through, BUT one of the feed pipes actually sucked in a little - a pipe on the right hand side of the engine. This suggests to me either an obstruction somewhere, or that I have air in the supercharger water system. So, does this cast any light on the problem, and is there anything I need to do to prime the intercooler system?

 

the intercooler circuit is bleed via the large bung with the large hex , up on top of the supercharger outlet manifold .
do not have the key on when you open this
an intercooler pipe may suck in a little when cold as there is not pressure in the system yet .
it will not do that at temp .
also confirm your temps with a $20 laser temp gun to rule out a bad temp sensor ..
also make sure there is enough coolant in the under guard mounted overflow bottle ,
so the main coolant system return can replenish on cool down .
a friend of mine had issues with this with this on his XKR causing slight over heats ,
i added coolant to the recovery tank via injecting coolant down the recovery pipe that goes to the neck of the header tank cap , and it fixed it

 

One thing to check is for debris in front of the radiator. Remove the cover over the radiator and look between them, If it has never been cleaned out, it could be completely plugged with debris, I know, it happened to me.

 

oldmots - radiator is clear. I'll pick up on your points, datsports and report back.

 

Three things: Check (replace?) the coolant expansion cap. Upon pressure, it is supposed to bleed water into the overflow tank (left side wheel well behind the liner). When things cool off, it is supposed to let water back in. If you have too much of that negative pressure, the cap probably needs to be replaced. It's just a cap, so pretty cheap. If in doubt, pull the liner off and check the level in the overflow tank. Should be at, say, half. When bleeding the air out, I have had good success by rapidly pumping the radiator hoses. It seems to dislodge trapped air pretty well.

Other thing is that is you have collapsing hoses, they probably need to be replaced. Radiator hoses are the usual suspects (I do not know enough about the supercharger plumbing). Not crazy expensive and good maintenance. Sometimes, they collapse under flow and prevent proper cooling. To me, if you have overheating at speed, it points to a water flow problem. Fans should only be a factor at low speed. It is reinforced by your observation that the cabin heater helps cool things down (that is a separate electrical water pump). Consider just throwing a new water pump. Cheap and fairly easy job (at least on my XK8, supercharger belt might have to be dealt with on yours).

Last thing: the Jaguar calls for DEXCOOL coolant. When you topped off, did you per chance mix with something else? DEXCOOL is incompatible with the older green coolant and causes gelling...

Best of luck, keep us posted.

 

Thanks, fmertz and all others. This is where I am at right now.

I believe that all coolant levels are fine. Coolant is pink, which is what the Jaguar people I have used put in, I am sure there is not jelling issue here. Supercharger cooling hoses seem good - actually I have recently had all hoses replaced as a precautionary measure, and they are all firm and new looking, and there is no water loss from anywhere (including the pump) Fmertz, are you saying that the airflow through the radiator, at speed, is sufficient to cool the engine, even with no fans? I think your suggestion of replacing the water pump is an excellent one, so I will carry that out. Are there such things as uprated pumps, and I have read elsewhere that one should go with a plastic-bladed one. Any comments on this?

Also if there are any forum threads on pump replacement, please point me in the right direction!