Hello Jaguar forum,

I have a car 1995 celebration model that I have owned for many years but has actually been in storage for the last 4 years.
Since taking it out I have noticed that under acceleration the temperature gauge goes above the N.
After acceleration (full throttle) it returns back to sitting on the lower part of the N.

What is normal behaviour on these cars? I can’t remember how the gauge used to behave under full throttle high rpm. From memory I didn’t think the gauge would ever leave the ‘N’ part but that said it was been quite warm in the uk for the last week when testing.
The car has a new thermostat, new fan coupling, new temperature sensor (Ecu), new radiator, aux fan appears to work (hard to test), new oil cooler radiator.
I don’t see any immediate signs of head gasket problems, the oil appears to be clean and the engine performs very well.
So is this normal behaviour of the gauge?
thanks

 

Ctxjs,

IME, AJ16 engines are really quite stable and incredibly reliable.

The major issue with the cooling system seems to be the propensity for the rad to get deterioration of the cooling fins in the lower third. This tends to manifest itself in a slight rise in the temp gauge when the car is sitting still in hot climate and with aircon running, as the rad cannot lose its heat as well without dissipating that heat through the fins. However, when the car is moving, the airflow though even a less-than-perfect rad is usually sufficient for temp to drop the temp straight away to Normal.

If I've understood correctly, your gauge is moving up as soon as you start to accelerate. I don't think that the coolant would increase in temp that quick and therefore move the gauge that fast. So I wonder if the issue is more a symptom of electrics relating to voltage. As we know, the instrument cluster readings can be a bit flaky if there is:

- any deterioration in the ribbon connector integrity
- less than optimal earth connections
- general earth inefficiencies on the car, particularly the bulkhead terminals.

So I wonder if the increased revs, and therefore improved alternator output voltage, means that the gauge is getting an improved input signal at that point?

If it were my car, I would start by:

- checking the alternator output at idle and see what change happens at higher revs (1500 rpm). Is it +14.1v?
- compare voltage readings (with and without engine running) at the battery posts vs the bulkhead terminals. Clean the bulkhead terminals if any difference.
- check the integrity of the gauge connections and earth points in the instrument cluster.

After all that, if you've still got an issue, I would try and hook up a connection to the CTS and monitor that whilst driving and see what happens to that signal when you accelerate.

Good luck

Paul

 

How old is the Coolant Temp SENDER (not sensor).

I would recommend plugging in an OBD2 reader and seeing what temperature the ECU is seeing. That is way more important than what is being reported from a completely independent SENDER. The SENSOR is reporting data back to the ECU, the SENDER just reports back to the dashboard. I never understood why they were independent of each other.

Personally, these two parts are cheap and easy to replace. I'd start with a look to see if they are both reporting the same data first before replacing, but I'd start there.