Hello, this Larry and I just flushed and filled my coolant system on my 2004 xj8 and I'm wondering about the temperature level. After it warms up the temp needle goes to the very middle and stays. My question is, is this normal? She does have 112,000 miles on her so. Any help is appreciated! Thanks, Larry
p.s. I absolutely HATE seeing that damn needle move at all lol

 

Hi, Larry, do you mean temperature indicating needle stays in the middle of the range? Yes this is perfect! mine with 65k does the same thing. as a matter of fact all cars that I owned, if cooling syste is functioning to as intended temperature gage stays right in the middle of the range.
P.S. how it the weather in beautiful Columbus, Ohio? Used to live there, left it about 30 years ago.

 

Thanks! It's very nice here today but temp drops again tomorrow for a few days...'tis the way here in Columbus this time of year. I was born and raised in Columbus and at times complained about it until I travelled all over the country and lived in Florida and VA for awhile until I came back a few years ago. I have a whole new appreciation for Columbus after all that lol.

 

Temp needles in cars are damped with a circuit to prevent deviation when they're within normal range, specifically to prevent people whining to the dealer that the temp "is all over the place." Well, of course it's all over the place! The radiator does its thing, the temperature drops a bit. As coolant flow gets cut off, the thermostat opens and hot coolant flows by the sensor and the temp raises a bit. You can see this fluctuation if you watch the data with a scanner, but the gauge is electronically damped to stay exactly centered if the temperature is withing normal range. It shows the car as cold when you start up, and if you have an issue, it will show the temperature climb, but as long as it's within the correct range, the gauge is locked on center.

My motorcycle forum I'm on gets two or three posts a month asking if the temperature fluctuation is normal. The gauge is a series of digital bars on an LCD screen, and "normal" is anywhere from 4 to 7 of those bars. These posts always ask "Is this normal? I think my bike's overheating!" We just ignore and laugh, and finally somebody answers, "Absolutely normal." When I answer, it's usually smart-***, like "Did steam come out of it before the temp went back down? Then it didn't overheat," or, "Did the temp came down after the fan came on? Yeah? Wow, normal designed function!" I {usually} refrain from using "idiot" in those posts.

 

Hey thanks. I'm just very spooked regarding my 2004 xj8 because the deal I got on it really seemed to good to be true. I'm always cautious about those too good to be true things in life lol. Thanks, Larry

 

Good information and be aware many have had the engine over heat BEFORE the temperature indicator (We really don't have a gauge) showed it. As posted above and verified years ago by a forum member the needle stays in the center over a range of temperatures. Not good.

Some us including me use the Torque Pro app with the custom Jaguar PID pack to give a actual temperature of the coolant. Pretty cheap way to stay on top of the over heating.
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@clubairth1 Where did you get Jaguar PID pack for TorquePro app for x350? Can you post a link to site?

 

Let me look as it was made by long time forum member Cambo in OZ for the 5.0 and 3.0 engines back in 2019.
Sorry I was wrong as Cambo only made them for the later cars and we never did get them for the 4.2L and 4.0L cars. There were some requests. Here is the original thread.

Custom Pid Pack for Jaguars

Does anyone use TP on the earlier cars?
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Exactly this, the gauge basically has three states: cold, med/operating temp, hot/overheating.

When I had a bad water pump and thermostat, I'd watch the engine temperature climb on my scanning app from 180-212F at normal conditions to as high as 240F. Meanwhile the gauge would not move from the center mark until about a minute of those high temperatures at which point it would go straight to the red hot mark and activate the overheating light. At that point I'd shut the car off to avoid permanent damage.

During this I also discovered that if you turn on the heat it will drop engine temperature presumably because the auxiliary water pump comes on to bring hot coolant into the heater core. Revving the engine to around 2500 RPMs when at a stoplight also helped, likely because it got the water pump spinning faster.

Over a year later now and thankfully I don't think the engine suffered catostrophic damage from the dozen or so times that it overheated but I was quick to shut it off when I couldn't use the above tricks to keep it from going north of 220F.

 

Turning the heat on doesn't really change coolant flow, but it opens air baffles allowing air through the heater core, and thus cools the coolant in the core, just like the engine fan does for the radiator.

Once upon a time, turning on the heater actually did open a valve to open coolant flow into the heater core, but modern cars have constant flow through the core and use baffles to regulate airflow through the heater core.

Raising RPMs is probably the worst thing you can do with an overheating engine. Sure, you're increasing coolant flow, but you're also assuming that there actually is coolant in there to flow, but mostly you're generating more heat and thus asking an already overworked cooling system to work harder.

 

There is a bleed screw on the coolant reservoir with the engine running keep repetitively squeezing both the lower and upper radiator hose at the same time too help push the air out then close the bleed screw drive the car around the block and recheck the coolant level. Make sure too only use OAT coolant many people on the forums including me uses DexCool it’s a very good coolant and matches the factory specs and dye color. Don’t overheat the engine and don’t put any additives into the coolant also ensure you have the heat on full blast and heat is coming out of the dash too make sure you have coolant flow if it any point the heat stops coming out the dash pull over and make sure you have coolant in the reservoir.

this would also be a great time too inspect the cooling system make sure there is no leaks or soft hoses and the clamps are secure. If you allow the engine too overheat with our engines being aluminum it will most definitely warp the cylinder heads and the block. Also inspect the radiator for any damage too the fins.

are cars have a coolant temperature sensor that only reads coolant temperature not cylinder heads temps the car will only indicate that it is overheating on the dash when the temperature surpasses 220-230 degrees so the second the gauge goes up immediately shut down the engine

 

I didn't know about the constant flowing coolant, great to learn. Would that mean the auxiliary water pump is presumably always on?

The revving I can tell you definitely worked in lowering engine temperature while I was stopped. I had to drive like this for about two weeks in city traffic. While driving at speed on the highway, no overheating issues but when I was driving in stop and start traffic, the engine coolant temperature would creep up and up. Once I revved it gently and held it at 1800-2500 rpm for 15 seconds, the temperature would drop as much as 20 degrees.

I watched the live monitor very closely during this time as I was afraid of damaging the engine.

 

this sounds more like your cooling fans are not operating correctly or you have a restriction in your cooling system. Check too see if the fans are coming on

 

As far as I know, it's always on, but I'm not positive about that.

One of the things I've done previously is shut the ignition off and coast, with the gas pedal all the way down, just allowing air to pump through the engine. Go to neutral and restart, get your speed back and repeat. I've gotten thee or four cars home that way, just a few miles, when they threw the serpentine belt so I had no water pump (or power steering.) You end up with just a few seconds of actually burning fuel for a few minutes of driving.