I'm asking here in the XK section because it seems like a lot more folks pay attention to engine parameters on these models. I've been dealing with pseudo-overheating symptoms on my XJ since last year, had changed the coolant housing back in January 2013. All summer long had to deal with pinging and the fan running on after shutdown. Found out that the fan was unrelated as I have had the PCM flash update that will run the fan to stop a fuel heatsoak issue.

Anyway, it's pretty chilly here now and I'm still getting pinging like crazy. I ran the scan tool on the way home today. It's 52 F outside, I'm cruising a steady 70-75 mph on flat highway, and the temperature is sitting at 199 F the entire 20 minutes I'm on the highway. I get off and at lights it will rise to 204 F and stay there.

This is with the a/c off, heat on 74 F, and steady road speed. Plenty of heat and car warmup seems fine (a few miles to full operating temp). Am I crazy, or should that engine not be sitting at 195 F all day long in this cool ambient? I feel like I'm going to be driven nuts by this car until I just break down and replace the thermostat again. (but I hate throwing parts at problems if I can't confirm an issue).

The funny thing is, during the summer, I would cruise in 90+ temps with the a/c on full, coolant temp would be 197 F, maybe go up to 199 F on a long hill. Now it sits there at 199 F and it has no heat load.

Am I off base? Or should I just throw $50 at a new tstat?

 

My 4.0L ran in the 198-202 range during the summer months (I'm in Texas). This time of year outside temps are in the 60-70's and it runs about 193-195.

I have installed a brand new radiator, new hoses, thermostat and given the blue cat a flush since the summer. Sounds like temp-wise you're not too far off. However, a new thermostat is a cheap fix, just in case.

 

and when you put in the t stat did you check the internal crossover pipe? they can break, crack and lead to running hot or over heating, on a 06 I would install a new t stat housing. Theyre $60 at partsgeek, housing, seals, and stat

 

My 4.2 sits at 203 on the OBD meter so long as you are moving. It pretty much doesn't matter what the temperature is.

New thermostat 1000miles ago when I did the water pump... and it was the same temp with the old one.

 

The whole housing was replaced back last January, was all broken up internally. That was under warranty at the dealer at the time.

This is what worries me... so I guess > 195 is normal for this engine. But I feel like it should be able to keep it right at 195 when the ambient is cold as it is now.

 

I would bet that the difference you are worried about is smaller than the error of the sensor measurement. You could try cleaning the connector and sensor electrical connections, it doesn't take much resistance change to show a degree difference.

The pinging probably isn't caused by the couple of degrees difference, but the couple of degrees could be caused by a lean condition if it's making the car actually run hotter.

What do your fuel trims and fuel pressure look like?

 

And without looking it up and going off of memeory i think there was a ecu reflash for pinging. But like i said without looking it up with your vin/model may/maynot apply

 

The OEM Jaguar thermostat doesn't fully open until 185f / 84C so running at around 195 to 205 would be normal. The fast fan speed would activate at above 205 if the temp was getting high, and would quickly bring it down to 195 to 205 again if everything is working as it should.

Also note that As the thermostat opens, it closes an orifice in the rear of the housing at the same time which normally acts as a bypass valve. Overheating can occur if the disk on the rear of the thermostat doesn't seal the flow of coolant bypass properly.

The radiator only has a single core in it, which seems crazy for a large engine like this and in hot climates would always be on the edge of its limits. I don't know why jaguar didn't fit a 2 or 3 core radiator for the export market.

 

Actually, I noticed that last week when I disconnected my battery, when I reconnected it the engine did not ping at all. After driving it around it started slowly pinging again. Last time I looked my LTFTs were around 10% if I remember correctly. I will check again.

Do you think the O2 sensors might be failing? Only 67k miles on the car now. The first drive after resetting my battery it seemed to have no pinging. But then, it should still have compensated using STFT regardless... that may just be an odd coincidence.

True--I had that done last spring at the dealer. My VIN was in the range for the vehicles affected. It only helped a little.

Yes, I noticed that myself. I've seen bigger radiators in 4 cylinder cars... one of my to-do items before next summer is going to be pulling that out and thoroughly cleaning it. I have already blown the dust and dirt out with compressed air, but probably not as good as cleaning the fins with soap and water.

 

When I was driving through the mountains my temp was getting close to 220 sometimes.