Hello,

My 2006 XJ8 has this odd problem where the car's engine temperature will keep increasing steadily while the car is idling with the Air Conditioner turned on. I know about the deceptive temperature gauge that stays at 50% for a wide range so I am using the Blu Driver scanner to monitor the temperature.

In a 7 minute time period the engine temperature went from 205 F to 249 F. I then turned off the air conditioner and in less than 2.5 minutes it got back down to 205 F.

If I'm driving the car on the highway no problem at all (stays around 207), but if there is a lot of stop and go traffic or long traffic lights in runs around 220.

Has anyone seen this before? I searched in Google, the two possible solutions (bad compressor, bad condenser fan) were already checked out by the shop I have it at. I tested the coolant, it has protection to 257 (125c).

Thanks.

For our friends in the UK

205 F = 96 C
220 F = 104 C
249 F = 120.5 C

 

Auxiliary pump???

 

Check both of your fans. Might be aux pump but doubt it. Regardless, you have an issue somewhere in your cooling system.

With AC commanded on both fans should be running at high speed.

Hope the above helps.

 

I too agree that you need to confirm the rad fans are coming on.

 

The aux pump is for the heating in the car so I doubt it is that.

Could be a sticking thermostat.

Are the radiator fans starting when the ac is on?

 

It's only for heat.
Here i thought that any need for more cooling, would also engage it.
Learn all the time.

 

Hi,

I was waitng until I got the car back from the mechanic.. He told me today it is leaking coolant from the intake manifold, that he needed to look inside when it was removed to inspect further. Perhaps the extra strain of running the a/c makes a difference at this stage of coolant loss to make an impact when it is idling. The coolnat leak is very slow, I drove about 100 miles (in one trip) a month ago amd did notice the coolant int the tank went down just below the “min” level mark, so I added some more. The radiator fans are working fine. Thanks for all the help. I”ll report back when it is repaired.

 

Has to be more than that. Take a peek at those fans

 

Hello,

So the car is repaired, I drove it last night then idled it for 9 minutes with the Air Conditioner on, the temperature held at 203 F (95 C) the entire time. Before it would keep rising steadily and at the 7 minute mark would have been at 249. They changed the gasket for the intake manifold, the thermostat assembly and two hoses. The fans were fine after all. Thanks everyone for all the input.

Frank

 

Good to hear it's all resolved. I was going to mention the thermostat assembly - I had a very similar issue when I first got my car (of course it didn't manifest itself for a couple of months until we got out of winter). I did notice the fan ran a lot, and it climbed the temp gauge in stop & go traffic once outside temps got over about 58 deg F. I notice the air behind the fan when it was running was fairly cool, and revving the engine up off idle brought the temp back down, so I suspected it was a coolant flow issue. Changing the thermostat assembly cured the problem.

Dave

 

Spastic plastic, truly a love hate relationship in today's world.
The logic for it's use as weight savings,for thermostat housing.
Is planned obsolescence, knowing good & well it will fail.
Aluminum is light, cheap, & will not fail from heat cycles like plastic.

 

Glad to hear all is fixed