Hi all,

I've been battling this one for a while. It all began when one of my cooling fans stopped working (bracket damaged/fan burnt itself out). I had the twin fan assembly replaced with a reconditioned unit...but the poor girl still gets too hot in traffic. This may have been happening prior to my damaged fans but I was never paying much attention to it - possibly fooled by the temperature gauge looking oh-so normal. I've since bought a $15 bluetooth device to connect to the ODB2 port, this has since confirmed my suspicions that the car is getting too hot.

Some facts:

• Cooling system not losing any water, pressure tested.
• Twin fans operating as normal as I can tell, they come on when the AC is on and when the car gets hot.
• Car only gets hot when stationary (traffic jams)
• When the car is already running, ie. not from cold, it heats from 90°C / 194°F to 100°C / 212°F when stationary for 15-20mins.
• Car cools rapidly when moving again - down to 86°C / 187°F

I guess the fans aren't cooling enough while the car is stationary or the coolant isn't getting moved around the engine quick enough?

Any ideas...anything a weekend mechanic can check before I book it in with my Jag dealer?

Thanks all.

 

It could be that the water pump is not moving enough coolant at idle/ low speed. Try shifting to neutral and increasing revs. The pump is inexpensive and fairly easy to change.

 

I had the same symptomes... My thermostat was dead.

When the engine is hot, feel the radiator (lift one of the top rubber covers). It will probably not be really hot at all.

My thermostat wouldn't open. It was stuck closed. The car would stay cool under normal driving conditions. In slow traffic though it would heat up and in a jam be really hot...

You can check this yourself. Remove the thermostat and put it in some boiling water. If it doesn't move, it is dead. If it moves, then the problem is somewhere else.

Do your fans run a long time after driving? Mine would ALWAYS be on. Unless the car was cold. But that is normal

Here is my "post section" in the "What did you do to your X308 today"

https://www.jaguarforums.com/forum/x...9/#post1217713

 

Couple of quick thoughts: 212*F is not all that hot (my fans come on at 205*F) if the fans come on and cool the engine back to 199* or so. Pure water boils at !00*/212* but pressurization and antifreeze raise the boiling point significantly.

No leaks, that is good. I would flush the radiator, change the TST and install a new water pump (lots of threads on all of these efforts on this forum plus many videos). Check the belts.

New antifreeze will probably help.

Whatever you do, be especially careful around those plastic overflow pipes, particularly the one running to the top of the radiator -- they break easily.

 

I had the same problem this past week. Sitting in traffic the fan would kick on, as well as once I parked and shut the car off. Went off and ordered the aluminum thermostat housing with new thermostat and haven't had a problem with the fan all week. Had completely forgot about the overrun hoses snapped one, was able to get .5" radiator hose from AutoZone and ran it from the tank to radiator with some clamps.

 

Having been through this condition recently in great detail I would comment that your temperature readings are not unusual. Here is the discussion resulting from changing the temperature sensor along with a leaking cross over pipe.

https://www.jaguarforums.com/forum/x...rature-138312/

 

Hey Test Point (not sure I know your real name?)

My car temperature has crept up to 102*C/216*F and only stopped because I got home :-) Its has in the past (once) been so hot even the dashboard temperature gauge showed it as hot.

@jhartz It's not a common practice to use antifreeze in Sydney.

I'm going to check the thermostat - seems like the easiest to fix and most common problem.

Not sure if this could be related, on occasion, prior to starting the engine and after the key is in the ignition, I hear a bit of a gurgling from the engine bay on the driver's side (RHD).

...will report back with updates :-)

 

We use the terms antifreeze and coolant somewhat interchangeably. Hoepfully, you are using the recommended 50/50 mix with water.

If anything, it sounds like your engine is running too cool at times. Thermostat is the best place to start.

 

+1 TST: UNLESS YOU ARE REALLY RUNNING STRAIGHT WATER (no coolant/antifreeze). If so, you are ^^^^ed!

But, hearing gurgling on the right side of the engine bay leads me to believe you are pumping small amounts of coolant and air exhausting from the water pump: which suggests the TST is stuck shut.

 

But if the thermostat is stuck closed, why does it cool down rapidly when the car is moving again, as noted in post #1?

 

It's stuck open which is why it runs too cool.

 

Because you have enough air in the engine bay to cool it externally.

Simply lift one of the rubber flaps on the top left corner and feel if your radiator is hot. Mine was always cold with the same symptomes...

 

1. Thermostat
Anyone know the thermostat part number (or alternatives)...I've got a bit lost searching, however I think the original part number is: AJ86484

Is this part a valid replacement? NEW Genuine Tridon Standard Thermostat FOR Jaguar XJ12 XJR 6 0L 4 0L 8E 9KP | eBay


The following items claim to be replacements for this part but fail when I attempt a compatibility check (on the ebay page).

Engine Coolant Thermostat OE Type Thermostat Gates 33079 | eBay
Engine Coolant Thermostat OE Type Thermostat Stant 13649 | eBay


The local products (Australia) are:
Tridon | industrial, automotive, hardware | Part Finder (you need to do a search for Jag / XJR / 2001


2. Manual
Good manuals (online or not) for the XJR like the old Haynes? I installed the JTIS (found in other threads) but it doesn't show me something simple like the engine bay/diagram/parts etc.

Thanks for any tips!

 

Rockauto lists Stant 14748 and Gates 33948 for the 2001 XJR.

 

Okay, I thought I'd test how long it takes for the cat to get hot when stationary, so I could retest after I've replaced the thermostat.

Interestingly enough if I sit stationary it starts to climb quite quickly, a degree (Celsius) every 2-3 mins.

I then noticed that if I switch off the Air Conditioning the temperature drops rapidly back down to normal - from 100*C (212*F) to 91*C (196*F) within about 5-6 mins.

Given this additional information does it make anyone think there may be a different problem? ...or should I forge ahead and replace the thermostat anyway?

 

I think I'd stop staring at the temp gauge and drive the car. What you're seeing is one of the reasons the gauges have been turned into the equivalent of idiot lights.

 

Mikey, you may have missed it in my thread, I'm referring to exact temperatures reported via the ODB2 interface

 

No, I saw that. Unplug your interface and the problem will disappear.

 

Thanks for your unhelpful posts Mikey.

My car's idiot gauge rises to maximum, the ODB2 interface shows the temp rising past 220*F and the auto trans starts to spin high/reluctant to shift in an attempt to cool down the oil and your advice is to keep driving and unplug the interface.

 

From the RealGauge web site:

"Once Jaguar's factory cooling gauge reaches about 185 degrees F, the instrument cluster forces the gauge to remain at mid-scale until the temperature reaches approximately 235 to 240 F. This allows virtually no time to react to an approaching overheat condition.

Overheating may be extremely damaging to our aluminum engines in a very short matter of time.

RealGauge will let you see normal fluctuations in temperature as you drive, depending on the outside temperature, how fast you are going, the engine speed, the condition of the cooling system, the engine controller switching on the cooling fans, use of heating and AC, etc.

RealGauge will give you more time to react to a potential overheating situation.

Additionally, by noticing changes to normal engine temperature patterns, you increase the likelihood that you can have cooling system problems (thermostat, water pumps, radiator, fans, etc.) evaluated and repaired before they become serious, expensive and potentially leave you stranded. This is especially important as our cars get older the chances of a failure in the cooling system increases.

What coolant temperature readings should I expect with RealGauge?

As with the factory gauge you will see the engine warm up from 125 F to about 185 F, which is midscale. The car should then operate most of the time in the range of about 190 F to about 215 F, but higher temperatures may occur at times of idling, high ambient temperatures and high RPMs. If you consistently see higher temperatures or lower temperatures, the cooling system and fans should be investigated."

I think what some are trying to tell you is that your temperature fluctuations may be somewhat "normal" and that is the reason Jag made the temperature gauge stay centered until things get really hot at 235 or so.

Are you a running coolant/water mix or just straight water? The coolant, also called anti-freeze here in the states, along with a pressure cap on the cooling system, raises the boiling point of the mixture so it doesn't "boil over" at 100C or 212F. That is a good thing.
Vector