Hello everyone,

been happy driving ever since the last problem has been resolved (immo issue), but must admit this Jag is a headache when being used as a DD.

Now it's the cooling system which is acting strange. I mean there's a blasting heat under the hood! The temperature meter on the dashboard is just fine, right in the middle, there aren't any red lights coming up or anything but the fans go crazy very, very often (2nd stage?), even when just calmly driving around the city; the gasoline consumption has gone up to 18,1L per 100km (4.8 gallon per 60 miles?) and I don't even use the AC.

When I sped up drastically (pedal all down) all I could feel in the cabin was a blastin heat coming from the engine - the cabin fans (AC) were off (minimum setting) and the temp coming inside was never this high...

It's currently 3-4C outside (37.4F) where I live. All the filters, oils and coolants were exchanged last year.

Does anyone have an idea what could it be? The radiator looks to be clean, I haven't found any leaks but the coolant level does not change - shouldn't it do so depending on the temperature of the engine?

Another thing is that the fans go off the moment I turn off the engine - I remember they should stay on for some time if the temperature of the engine is high?

Thanks for reading and in advance for your suggestions!
Atramentous

 

The first thing to consider is that the temperature gauge is nothing more than a "idiot" light. Once it actually reaches high temp it is too late. The first step in diagnosing the problem is to get an infra red no touch thermometer and scan over the engine and check the temps of the engine, the upper and lower radiator hoses and the water temp in the reservoir. That will give you a few answers 1. what the real temperature is, 2. if the upper and lower hoses are the same temp the thermostat is probably good. reservoir temperature compared to the hose temps will let you know if the water pump is working.
Besides the water temperature readings you need to scan for OBD codes and let us know what they are. Also if you can get them we need to know what the short term and long term fuel trims are.
There is a lot of possibilities so the more information the better. It is a far better way to proceed than just start changing parts and hoping.

 

Atramentous, are the various functions of the AC/heat working normally? In other words are you able to control the cabin temperature level and change the air distribution modes? When was last time a coolant service was done? Your fuel consumption is high, but am not sure that it's related; what is condition of engine air filter and spark plugs? Is Check Engine Light (CEL) on?

 

Thanks for your responses!

I will try to measure temperatures as suggested and get the OBD codes but this may be hard at the moment. Last time the Jag was being checked, we've had some OBD code indicating throttle fault - do you think it could be connected?

The AC seems to be working normally, I can control the temperature as long as AC is on, when I turn it off the heat comes inside the cabin and there's no way to stop it.

CEL is on but only before the actual launch, once engine starts, the light goes off. Coolant service was done last year, around April. The same applies to air filter and spark plugs I suppose!

 

Hello guys,

I am just bumping this thread as the problem is still persisting (I just don't drive the Jag that often anymore and don't have much spare time to get rid of it finally) and got to check with the computer that the engine temperature when running is between 96-98 Celcius Degrees (approx 206 Fahrenheit).

Would you say this is too much? The fan keeps on going crazy nowadays, since we got hot summer weather, yet all the dashboard sensors show that temp is in-tact... looks like it is having really hard time to cool down the engine.

In regards to OBD codes, there is one connected to throttle (the computer did not show the PXXXX number...) and few other ones related to cabling/bad fuses. Perhaps the radiator should be changed? I don't think it has ever been.

 

Below I have attached the cooling fan operation details. 206 would be a nice normal operating temperature. When the engine is running and the AC system is on the ECU will automatically kick in the fans to prevent overheating. AC on means automatic fan running.
If the fans are acting erratic then you probably need a new ECT engine coolant temperature sensor. The simple test would be to use a coded reader that can check engine temp. While observing that reading take an actual temp reading at the hoses and compare the results.

 

Thank you so much!

The above is very useful piece of information!