At an ambient temperature of 86°F, according to RealGauge:

• Idle temperature is around 217°F, both fans are on in high speed
• At 55 mph needle stays at or near 215°F
• Above 80 mph, the temperature drops to about 205°F
• When going up an extended incline at about 1800 rpm, the temperature can go as high as 220°F, the highest I have seen is about 225°F.
• Stabbing the throttle for a quick blast of acceleration to about 90 mph brings temperatures down by about 10°F in about 30 seconds.
• Fans stayed on this last time I drove the car four minutes after turning off the car, when the coolant temperature reached 200°F.

The RealGauge alarm has never activated. At what temperature is it programmed to go off at? Would a low temperature thermostat improve my coolant temperature?

I have also read about the Bosch 010 intercooler pump and I know DCR sells a larger aluminum intercooler radiator. Would all of these help my car run cooler or are the temperatures I mentioned normal? Or is this just a bad thermostat?

 

Sounds about right to me.

 

I used my Ultragauge on a 2000 XKR that I was working on a few years ago and never saw over 208 in similar conditions. I have learned that thermostats can vary widely. I replaced the one in my 06 XK8 and the temp stayed around 175 as long as I was moving. Replaced that one and now it stays 197- 201 when moving. The fan comes on at 204. So I would start by changing the thermostat, maybe the water pump.

I had a Realgauge in my 97, and I thought the alarm was supposed to sound at 220 or 225, but that was years ago and I could be wrong. Contact Steve at thejagwrangler.com and I believe he will get back to you quickly.

 

Seems high. I would start with a nice chemical (Prestone rad cleaner) cleanup of the cooling system. I have done a heater core cleanup like that a couple of winters ago with _dramatic_ results (warm air in the cabin starting within a couple of miles instead of 10+ miles). Somehow, it looks like the cooling system internally coats itself with some deposits that work against heat transfer. The chemical cleaning gets rid of all that and restores better performance.

As you are opening up the cooling system, would not hurt to throw in a new thermostat.

You can also try and run the heater on full (PR, I know) to see if the temp drops. If so, it might mean the thermostat is wide open, but somehow the main radiator is not cooling properly (!?) or the water pump is not moving enough fluid (!?).

Separately, and after a nice cleanup and refill with new Dexcool, look into a heat transfer agent like water wetter.

In my view, at any type of speed, you should be hovering around the high 190s and low 200s. Of course it goes up as you stop. Remember, A/C on means fans on as well, but not on high.

Best of luck, keep us posted.

 

My water pump is only a year old, I would hope it’s still good. My thermostat is about 4 years old, so that may likely be the problem. Interesting on the variations you noticed.

I did that precise rad cleaner last year, also I replaced my rad a little later due to a leak in the end tanks. My water pump is also the same age as my rad. All hoses are less than two years old. The temperature does drop with the heater on full but it takes a few minutes. I had been considering water wetter before, I think I will use it when I find out what the problem is. I think it’s the thermostat.

Is a low temperature thermostat, such as the one Eurotoys sells a good idea?

 

Thermostats set the low engine temperature, not the high point.

Changing one would only help if the one you have is not opening fully, or not opening at the prescribed temperature. There are many topics on this forum of thermostats failing to open or failing to open fully.

Some even suggest changing thermostats every 2 years as a preventative measure.


Before buying parts or doing anything else, take off the top plastic cover that is over the gap between the transmission cooler and the radiator. When I took mine off a few weeks ago it revealed a radiator front that was caked with dust and insect debris. Not ideal for cooling purposes.

With a regular garden hose with an adjustable nozzle you can direct a stream of water into the gap and carry away the blockage if you have the same situation as I did. In my case it took 3-4 minutes to totally clean away the offending mess.

when I was troubleshooting cooling issues for my restoration shop, I’ve found the quickest procedure is to start where the heat is produced and work outward.

To wit, as already suggested,

(And in this order )

1) start with a cooling system flush. The Mercedes citric flush is well known and liked

2) Take out the thermostat and either just replace it with a quality item, or at least test it in pan of hot and near boiling water (with a thermometer) to see when it begins to open.

3) remove water pump and examine the impeller. The (plastic) impellers are well documented for having. issues

since you state the fans are running OK, the above steps should yield some modest results if your radiator is not severely plugged up beyond the help of a citric flush.

in comparison, here are the numbers from an 1,100 mile trip I took over this last Sunday and Monday. Driving from NE Oklahoma to central Texas (Austin) The ambient air temp ranged from 95 to 104 F.

At speeds from 55 to 70 mph the engine temp ranged from 196 to 210. When going slower or stopped at a light in towns, the temp would go up to 215-220. Above 75-80 mph the temp would always eventually come down to 186 to 195.

Since one cannot always travel over 80 mph, clearly the ‘02 XKR could use a larger air intake or failing that, higher capacity cooling fans to mimic the high speed air air flow that always seems to lower the coolant temperature.

My coolant and oil temperatures were monitored using the Autool X-60 gauge. I’ve been using it for 3 year, it has been very reliable.

Oil temperatures are almost always 15-17 degrees F higher than the coolant temperature. That puts my oil temp nearly up to 240 F at times. No problem for a quality synthetic oil, but anyone using a conventional dino oil might think about going with a synthetic oil. Conventional oil is going to be breaking (oxidizing) down around 240-250 F , so those temperatures are giving one no safety cushion. Synthetic oil can tolerate a much higher temperature, 300 F +.

Z

PS re WaterWetter, it doesn’t do much when added to a 50/50 antifreeze mix. However, it does pretty good ast lowering coolant temperature 10-15+ degrees F when used with distilled water or at most, a 20% antifreeze mix. My antifreeze mix is about 15% antifreeze (measured by refractometer). In the winter I’ll use 50/50.

 

More cooling system information:

 

I removed the plastic cover above the radiator and checked the core. It was clean and still looking like new. My coolant level is fine, and I have no leaks in the system. My intercooler pump is working, although I heard a whirring noise I had not noticed before. I’m not sure if that is normal.

How can I test the water pump I put in last year without removing it? My radiator is less than a year old, and when I changed it, the old one didn't have any buildup on the inside. I have no reason to believe my car needs a chemical flush when most of the cooling system is new.

Today’s ambient temperature is 93°F. I will drive the car to the gym and pay attention to the RealGauge. I am thinking of throwing in a new OEM T-stat and upgrading my intercooler pump to the Bosch 010 unit, which the twin-screw guys advocate and, flushing the system and filling with a 70% water, 30% Dexcool mix with WaterWetter instead of the 50/50 I have now. That may help improve cooling efficiency. Thoughts?

 

yes. the high speeds turn on at 105c/220f. original gauge moves at 115/240. still plenty of warning

even with the undersized delco water pump i can idle all day long at 98c/210f with 90f ambient

 

I don't have the original idiot gauge, I have the RealGauge, which tells you the real-time temperature of the cooling system instead of reading in the middle of the scale. Why is your water pump undersized? At this point, I think I may have a sticking thermostat.

 

The RealGauge audible alarm will trigger at about 230 F.

 

Thanks Steve. 230°F is when the red zone in the gauge begins. Good to know.

 

Ambient temperatures are between 90 and 95°F. I drove a few miles and here’s what I got:



Starting temp after the car has warmed up: 200°F



After a bit of driving in the city. Temp is about 213°F.



I pulled onto a highway, steady 60 mph. Temperature dropped to about 207°F.



At the incline passing another car at about ½ throttle input. Temp is about 217°F.



35° incline on the highway at 60 mph; temp is 215°F.



It started raining ambient temperature dropped from 94°F to 84°F, temperature is about 213°F.



Traffic slowed to 35 mph, temp rose again to 215°F.



Traffic picked up again, accelerated to 60 mph. Temp was about 217°F.



At a stoplight for about a minute. Temperature rose to about 219°F.



A bit of hard driving, with revs reaching up to 5k rpm then stopped at a traffic light. Temperature hit about 222°F. When the car began moving again the temperature soon dropped to 215°F.


I am currently idling at the parking lot of the gym, with an ambient temperature of 90°F and the car has maintained the temperature steady at 217°F.

What do you guys think?


Edit, I just turned off the car to go for my workout. The fans stayed on for less than 2 seconds after shutting off the engine.

 

Those are close to my numbers except my ambient air temperatures are 95 and up.

certainly not overheating, but a little lower wouldn’t hurt.

can you check the real gauge against the OBD-2 output ?


Z

PS I think it’s unrealistic to expect every one of these 20 year old cars to have identical numbers.

 

I'd say the same, try and validate the numbers against another base. First, check the gauge numbers line up with what the OBD value is. Then maybe check what a laser thermometer reads in the vicinity of the sensor (it's metal on an XKR, right?). It's almost like you are reading 10deg high.

 

RealGauge uses the same computer data extracted from the water temperature sensor as you would read over OBDII. I would expect they would track closely in a 2004 model.

The pre-2000 cars have some coolant gauge variability issues which were resolved in 2000 and later models. That is why we designed RealGauge with a calibration feature should it be needed. We normally only send the RealGauge calibration instructions and kit with the '96-'99 models, however if you find that there is a discrepancy let me know and I can send the calibration kit to you at no charge.

 

I’ll see what I can do, but my OBD-II scanner does not do temperatures. I may have to buy a better scanner.

And an IR thermometer.

I don’t think RealGauge is inaccurate because when I drove from the gym to pep boys to see if they could use their OBD-II to check the temp, the fans stayed on for a few minutes after I shut off the engine. That tells me the temp sensor must be close to the RealGauge values.

Also, they wanted to charge a diagnostic fee just for that. I would rather buy a better scanner.

 

Water temp is basic OBDII, a cheap ELM327 will do.

 

My OBDII reader gives me water temp via a cellphone app, which I monitor 100% of the time. My '05 4.2L would climb to about 208* F at stop lights around Las Vegas in the summer, but back down to 203*-204* for normal driving in town. Crossing the desert to southern California in 115*F heat, it would rise as high as 218* F while climbing long hills, prompting a high pucker factor (I didn't know that that wasn't really excessive). I would shut off the AC, turn the heater on, and open both windows going up hills in an effort to keep it from going higher, then turn the AC back on and close the windows only while cruising level or going downhill. Did not impress my bodacious red-headed GF at all... A new 185* thermostat & housing, a flushed radiator, and a new reserve tank (and cap!!!) brought my car back to 195*-204* normal operating temps both around town and on the road; nothing higher than 208* noted since then.

 

Yeah, I am still suspecting the thermostat, but I will test first before opening the system and throwing parts at the problem.

I bought an IR thermometer that I plan to use tomorrow. I also bought an ELM327 wifi/bluetooth code scanner. If the temps seem fine this way, then I might suspect the coolant temperature sensor.