I have a 1989 XJS V12. On a normal day of in town driving my gauge shows about 1/8 inch below the N. On a hot day right at the N. If using air it is about 1/8 inch above the N. Is this considered a normal temp, Thanks

 

I suggest a laser thermometer and when each of these events arise, check the actual engine temperature, that will give you a benchmark reference for your particular engine / gauge.
The gauges in our cars can be flakey and very individual.
you will then have peace of mind and trust in the gauge reading.

 

About "normal" in my opinion.

BUT

It depends on many things, some are:

What temp stats are installed, and how old are they
How long since the rad was out and cleaned inside and out
Is the fan hub arrangement up to snuff
The Barrel Gauges are ONLY a guide, never promoted as anything more.
The ACTUAL pressure cap on the header tank, how old.
The foam pad above the transmission may be blocking EXIT air from the engine bay, it does happen, and if that air connot get out, things heat up.

Many more, but thats the common ones from my many years with these beasts.

 

Morning all.
What I have found with mine after I filled with Evans waterless coolant last year and getting a bit paranoid about temperatures and fitting an engine guard temperature monitor which monitors the temperature of each bank from the back of the cylinder heads is the following.
Normal running shows around 85-89c on each bank which is equal to dash gauge not touching the bottom of the N.
Sitting with the car idling temp goes up to around 90c which will be at the bottom of the N raising to around 95c which will be the middle of the N. Once the engine is revved temps start to drop quite quickly. My auxiliary fan will cut in and out when needed and I also replaced my fan and clutch last year which makes a lot of difference. My car has 82c stats fitted. I have also checked with a laser gauge and it shows the same as the engine guard. Hope this helps.
Rob,

 

A long time ago, twenty years I reckon, some XJS owners (including me) compared infra-red reading versus gauge readings. There was a huge disparity. For example, the bottom,middle, and top of the "N" on my car was (something like) 180ºF, 190ºF, and 200ºF.

The next guy's car was 165, 175, and 185. The one after that was 190, 195, and 205.

Those numbers from vague memory....but you get the idea!

I'll take advantage of this opportunity to beat my usual drum: 'tis coolant flow throughout the engine that should be our primary concern, more so than coolant temperature.

Cheers
DD

 

water boils at 212 degrees F with antifreeze it boils at 235. Under pressure of the radiator cap it boils at 250 degrees F.
Use a lazor temp guage ($25) right where the temp sender is.
As long as the coolant isn’t boiling it’s doing what it was designed to do.
The middle of the guage is normal. Don’t try to get the temps too cool, it’s hard on the engine to run cold. Plus your fuel mileage will go down.

 

For people using the IR digital thermometers, where is the best place to take the temp? I almost posted the same question last week, when it was actually hot in WNY. I've tried multiple locations. The first place being right next temp gauge sensor is (on the metal), but with the heat escaping, my thought is that area is higher than the actual coolant temp? Is a rubber hose better?

 

Consistency is most important. I use the spot where the temp sensor is. That’s as hot as it’s going to be.
That’s where the coolant is leaving the engine going to the radiator to be cooled. The lower radiator hose is where it will be as cool as it gets. Before entering the engine to cool it.
The difference between the two locations is how effective the radiator is.
Surprisingly perhaps, the stock radiator is more effective than those expensive aluminum aftermarket ones.