Hi Guys,

I just bought a 2003 XKR convertible. I think the engine temperature sensor is failing. When driving the indicated temp will jump from normal straight into the red. The engine temp is still normal but it indicates overheating on the gauge & goes into restricted perf mode.
I have a new sensor. Do I need to drain some of the coolant before swapping it or can I just unscrew the old one & quickly bung in the new one?
Thanks in advance
Jeff

 

Have you confirmed with an IR Temperature Probe that the vehicle is not actually overheating? If not, I personally would STOP driving the car immediately, until you had this sorted. The instrument cluster temperature gauge DOES NOT indicate the actual engine temperature. It goes to dead center and stays there unless you have installed aftermarket gauges, FYI, a forum member has come up with a solution for this, search for 'RealGauge', this will make the factory gauge work for real; he also has RealGauge for oil pressure as well, as the factory gauge does not display actual readings either. The temperature gauge will stay at dead center until it overheats, and then displays the overheat exactly as you have described, by shooting up to the red; the problem is that by then, it is almost certainly too late, as damage may have already occurred.

Also, if your engine temp is critical, the fans should be roaring like a MF. The fans in the 2003 are variable speed, and when they are operating at high speed, you will know it.

 

You might loose a few ounces of fluid . . . . but really overheating is a greater threat. An IR thermostat device is your friend. Less that $10 on eBay.

 

For a direct answer to your question- yes you need to drain some coolant, but if the engine is cold and you remove the sensor and quickly install the new one you won't lose much coolant and can just top the system off. Having an assistant to cover the hole while you fumble the parts will help.

But note that everything 03 XKR said is valid and should be considered.

Replacing the thermostat is also a good idea, and if you don't have records indicating that the system was flushed in the past couple of years that would be a wise move.

So maybe draining the system, replacing the sensor and the thermostat and looking for hoses that need replacing would be your best choice.

 

Thanks for your responses. When it first happened had been running on the hwy for an hour or so & just jumped from reg temp into the red in literally a second or so. Pulled over, no fans going. No excessive heat form the engine (I could hold onto radiator hoses etc). After 5 mins I opened the coolant res & there was no excess pressure. Started it & temp indicated normal. Stopped at the next town & had a mechanic who was also an auto electrician look at it. He confirmed it was not overheating, did a few tests & said he was almost certain it was a faulty sensor.
It continued doing this for the remainder of the trip. I stopped repeatedly to check under the hood. The electric fans were never going & temp felt normal. as soon as you restart the engine it goes back to displaying normal temp.
Does this still sound like a faulty sensor?

 

Regarding the faulty sensor:
I do not know. There was a recall to fix the instrument cluster due to some soldering issues on the board. If that recall was addressed, you can tell by removing the knee bolster, and the face plate for the gauges pulled out slightly so you can see behind it, and look for a yellow connector on the right side bottom of the gauge cluster, the one on the left will be white. If both are white connectors, this was not addressed, and it may be causing the erratic console behavior.

Regarding the fan operation:

Were you running your A/C at the time, or have it set to 'auto'. I ask because regardless of the engine temperature, when you turn on the A/C, the fans turn on automatically and run continuously at low speed, until you turn off the A/C. So, if you are getting no fans at all, especially with the A/C running, and while stopping during highway speeds and idling? to check the temperature, the fans should have been running at some speed and you need to find out why they are not.

After I exit the highway after driving at highway speeds and then normally through the residential streets to my house, a few blocks, by the time I have gotten home, and am idling into the drive, the higher speed kicks in, and discharges volumes of hot air from the hood vents. After idling for a minute and a half to two, fans blasting on high, they slow down to a low speed, then stop altogether. Then I shut off the car, as I do not like to shut down a hot vehicle when it is obvious that it is in the process of eliminating excess heat, whether or not it has a circulating pump to keep 'hot spots' from forming in the block after the engine is shut down or not.

I know there is a fuse chart somewhere on the forum, I would be looking for blown fuses and relays for the fans, and checking the connector plug that runs along the top of the fan shroud.

I had a problem with my 'chime' not chiming, and the seat belt 'bong' not a bonging, turned out to be a dislodged relay in the engine compartment left hand side fuse box; it appeared to have just popped out. I snapped it down and it seated tightly, now the chimes and bongs come through loud and clear. Perhaps you should check out all the fuse boxes throughout the car, 5 or 6 boxes I think, and see if any relays are dislodged or fuses blown.

If you have an owners manual, it will have the location for the fuses and relays in question. If you did not receive a manual when you bought your awesome choice of model year and body style, I did not receive one with mine, you can download it, and tonnes of other useful information, diagrams, and schematics, from the forum links on the main X100 post page.

Most of all, looking to the future, after you have fixed this issue, search for 'green shower', and follow the precautions and warnings, before operating your top, especially in hot weather where the car was sitting exposed to the heat.

 

If the temp sensor is telling the ECM of an overheating situation reported on the gauge the ECM should be telling the fans to come on. If your fans work normally with the AC on or otherwise I would lean to the identified dash problem.

 

Thanks for your responses. The fans do work - I've heard them while pottering along at low speeds, however whenever this fault occurs the fans are running normally if at all. All of which seems to point to normal operating temp despite gauge in the red.
P.S: Absolutely love the car - incredibly easy to drive long distances & upon arrival I find I don't even want to get out of it...!