Dear All,

my xjs V12 6.0, always when it is in temperature, has the needle of the water temperature that is slightly to the right of the N.

Doing some stretch or some queue, the needle moves a little more (without reaching the red, always within the normal range) and then return to the initial position as soon as you slow down or cmq there is constant flow of air.

How do they behave?

I'm thinking of replacing the thermostats and cleaning the radiator.

The car has 68 thousand km.

 

Nothing much to worry about. BUT, renewing the thermostats and cleaning the radiator and oil radiator fins, and the gap between the two, is avery important maintenance item. So do it sooner rather than later, say I.
At the same time, renew all the coolant hoses, and while you have access with the rad out, renew the drive belts too!

 

The thermostats are too often overlooked in this car. People have cooling issues and immediately jump to radiators and dual electric fan mods.

I would say definitely do the thermostats, that also gives you a chance to top off the coolant and get air out the system. Check the function of both fans and inspect the condenser and radiator for debris.

Get an IR thermometer for troubleshooting. If my gauge ever reads high I immediately start checking temps in the engine bay to see if its just my gauge or the real deal.

 

I had a similar situation, and rather than mucking about, just replaced pretty much everything - radiator (which was pretty mucky), fan, hoses, thermostats.

How far mine goes beyond the middle depends very much on external temperature, but anything more than a needle's width gap between the needle and the middle mark worries me, and usually means I'm missing some coolant. In cooler weather, so long as traffic is light, she'll hover a needle's width or more below the middle mark. Now, when it's about 20 degrees outside, normal town driving has her bang on the middle. But I've been assured by the experts here that there's only a few degrees of difference before and after the middle mark, so as long as the needle's in that general vicinity, and doesn't keep going up and up and up, your engine should be fine.

 

Quite true. I have electric fans, and to prevent undue on/off cycling in traffic I have an "On at 87/off at 82" degrees C temp switch.
When the fan comes on at 87 the needle on the gauge is at least 1/3 of the way above the N.

 

I'm not sure if there are some typos there, but if your car runs hotter while stopped in traffic you should probably check out the fans on it.

My 5.3 stays right where it should with everything in place, regardless of whether I'm stopped or moving. This is about 1/6" under the N with an 82 deg.

 

I think you have misunderstood. If the main electric fan ran all the time, the temps and the gauge would not move. Because it is on a thermostatic switch, there is a 4 or 5 degree cycle. My point is that an insignificant temperature change of a few degrees has a quite large effect on my temp gauge, therefore the OP need not worry unduly about his gauge readings.

 

I have had 3 gauge senders in my car and each had the needle at a different point on the gauge at the same temp (measured with a calibrated Fluke 187 and K type thermocouple).

What is more important is that the needle does not continue to climb. It will vary, mine does with the AC on.

 

Thanks for all the suggestions.

I will proceed in this way:

- thermostats
- cleaning of radiators

The coolant has been already replaced 2000km ago.

If it will not improve the behaviour, I will try to substitute the clutch fan that could start to work later respect to the original tuning.

As last, I will substitute the radiator, whose internal ducts could be plugged.

Another inform: which is substitution interval for the spark plugs, I think they replaced them in Jaguar around 40k km, now it has 68k.

 

All in all a good plan. But quite honestly, while you have the rad out, you might as well replace the fan clutch anyway. It is far easier to do, rad out, and will be beginning to get tired anyway.
Regular plug changes are important. I would do it, and thereafter ideally every 10,000 km; certainly 15000km maximum. The HT side on the HE engine has a very big job, and keeping all in top shape is very important for longevity of the electronic and other components.

 

Agreed!

Do it all, do it right, do it once. Ala carte = more misery !

I agree with the sentiment and rationale but those intervals seem very short to me. I'd feel safe in at least doubling them, personally. Even in the dinosaur era of carburetors and points-type ignition 12,000 miles (19,000 km) was the typical suggested interval

Or, remove a few at 10,000 km for examination and go from there.

Assuming no mixture control problems or piston ring/valve guide problems they'd probably look good as new. If not, repair the problems or adjust replacement intervals accordingly.

Just my 2-cents


Cheers
DD