Weird Temperature Readings

[sshaunus308]

Hi
What might be the problem? I had my water pump replaced some months ago. Since then, the temp gauge, I assumed, wasn't working probably. It seemed to be not registering any temp sometimes, and sometimes it barely moves. Before, it would read around half way. (I'd for a long time, had a minor leak at the pump until it packed up completely). Suddenly, the other night while on the M25, the gauge shot into the the red and the high temp light came on. I stopped as soon as I could and let it cool down. The engine wasn't overheating though. No steam or loss of water. I eventually got home. The fan stayed on for a good while after the engine was turned off. Drove it again after a few days, same thing happened. Water seemed to have dropped a little but still no overheating or loss of power. Mechanic checked and said the pump was operating and there were no leaks. What seems to be the problem??

Temp sensor faulty?
What is the normal operating temperature of the diesel engine? (I read the temp from the ECU)

As I said, there is no steam or overly hot temp from the engine and no loss of power or anything else strange (except for my heater not blowing hot air if that has anything to do with it...)

There are no fault codes either

Also, today, while returning from the garage, it shot into the red, but when slowing down to a stop, the gauge dropped a little. Almost as if the reading was partly dependant on the speed of the engine

Any suggestions would be appreciated

Thanks

[Andy P]

Hi Shaun,
If I was you I'd be looking at changing the coolant temperature sensor.
They are not expensive and at least it will eliminate it as the source of the problem if it turns out not to be that.
Not too hard to do yourself if your handy with the old spanners .
Got to be worth a try.
Good luck and stay safe.
Andy

[steve_m]

+1 on that, had exactly the same on my X Type, new sender fixed it.
You might want to look at the coolant loss as a separate issue; mine had a microscopic leak from the bottom corner of the radiator.

[J44EAG]

The same on my old V8 S-stype and later on my XJR350. Both temp sensors failed at around 80k miles. The same and other symptoms as you describe. A duff sensor causes fault codes, difficult cold starts, an erratic temp guage and poor general running. Mixture control goes out of the window...... £8 or thereabouts fixed the problem in minutes.

Be advised. Do NOT buy an after-market replacement sensor. The internal values are often incorrect which cause further issues. Buy only a genuine Jaguar part. The same advice goes for most of the other sensors found on a Jaguar. Genuine only.

Mike K

[Astromorg]

This same scenario occurred in my X type two or three times and was certainly due to some slight corrosion between the sensor and its connector. A thorough clean up and there have been no repeats in a few thousand miles.

[sshaunus308]

Thanks for the advice and suggestions. Will have a look at the sensor. Or rather, tell my mechanic to. It’s far too cold for me to be poking around in the engine bay myself....🥶

Will this have anything to do with why my heater isn’t blowing hot air as well? My heated seats have had to be working over time..

[Astromorg]

That could well tie in with your temperature gauge inconsistencies! When things go wrong, it's more often than not something associated with recently completed work that in this case was changing the water pump.

My first thought is an airlock in the coolant system. I wonder if those who replaced your pump knew of the bleed point on top of the engine that is hidden from view and requires both the air cleaner and its mounting bracket to be removed to get at it? When the system has been filled and bled, the following is the recommended, additional air removal process:

Start the engine and maintain an engine speed of 1500 revolutions per minute (RPM) for 20 seconds. Switch the engine off. Fill the coolant expansion tank to 15mm above the MAX mark. Install the coolant expansion tank cap.
Start the engine, allow the engine to idle for a two minutes. Observe the engine temperature gauge. If the engine starts to over-heat switch off immediately and allow to cool. Failure to follow this instruction may cause damage to the vehicle.
Raise the engine speed to 3000 RPM and maintain at 3000 RPM until the engine cooling fan operates, while observing the engine temperature gauge. If the engine starts to over-heat switch off immediately and allow to cool. Failure to follow this instruction may cause damage to the vehicle.
Allow the engine to idle for a further five minutes. Switch off the engine. Allow the engine to cool. Remove the coolant expansion tank cap. Fill the coolant expansion tank to the Max mark. Install the coolant expansion tank cap.

After that it could be a problem with either the coolant thermostat or the oil cooler thermostat, but you'd really need the temperature gauge to be sorted before being sure of them being faulty or the heater flaps might need re-calibrating (easy!), but let's not get too far ahead of the more likely solutions first.

[steve_m]

Or, just change the temperature probe; a few quid and less than 5 minutes effort.
Then go on to the deep stuff if it doesn't work; at least you will be starting off with a new sensor.

[J44EAG]

I agree with Steve.

I`ve never had a temperature sensor last more than 80k miles! Change at each and every 80k interval and at least you keep a suspect and somewhat limited lifed part out of the failure frame. Thermostats can go on rather longer but seemingly even reliable items wil become erratic after high mileage. I recall Rob Jenner telling me to replace a high mileage stat. I did and the car perked up. I didn`t even realise the old stat could have such an impact on the way the car ran. In the case of a V8, Jaguar decribed the colling system as "precision". Without doubt the improvement in running with a new stat fitted settled the engine and improved dash temperature guage response. If you don`t believe me...try it yourself. Stats don`t cost that much but ONLY fit a genuine part. I`ve had real issues with after-market stats when I`ve tried to save a few quid and ended up with a car that ran like a bag of poo!

Mike

[sshaunus308]

Well, spoke to the mechanic briefly today. He’s says I have
1. A small radiator leak which I guess explain the loss of coolant.
2. Block heater matrix which explains the lack of cabin heat and
3. A dodgy coolant temperature sensor.

Something leads me to believe that they’re all related to the same issue being along similar timelines

[J44EAG]

A blocked matrix is likely to be caused by internal coolant system corrosion, the bi-product being sludge which blocks coolant system components.

Its the same in a home central heating system where sludge can bring the system to its knees. How do I know? Well, I had the heating man in to deal with an issue on my Mothers system and we decided to fit a magnetic Magnaflow filter to catch the crap caused by forty years of system neglect. You should have seen what that filter removed! That scenario is little different to a vehichle that may not have had regular coolant fluid changes at prescribed intervals or has had the incorrect anti-freeze installed.

Sensor failure? Old age combined with high mileage. A well known issue and worth a component change at 80k miles to preserve reliability.

Mike

[sshaunus308]

....so, because of the time it takes to remove the dash, sorting that heater is something I’m probably going to try and do myself. I was told by one, that it was a blocked matrix and another, that it was the internal heater vane things that are stuck so hot air isn’t able to be diverted into the cabin when needed. (I actually remember hearing the motor sounding a bit rough not too long before)

Radiator leak... is it worth buying from eBay for £60 or £70 instead of the £200ish for an official jaguar part? What should I consider when buying?

[steve_m]

Something Japanese.
Generally much more reliable.

[info343]

I have strange problem. X type estate 2006 petrol V6 2.5
Sometimes if I drive at 70 on the motorway for a while a red warning light comes on - the display says high engine temperature and the temp gage goes right up. seemingly there is nothing wrong with the car and it funs more or less normally - ie I'm able to drive home normally.
The AA came out a few times ago and said it was running normally. sensor changed and it's just done it again.
Any experience - ideas

[sshaunus308]

I've not sorted mine as yet. Same problem. I found a leak in my expansion tank today that wasn't picked up before so it was loosing pressure and coolant as well. It didn't show up in pressure tests and only seems to leak when under more pressure, like driving above 50 etc. Going to have that seen to firstly and see if that does anything for the problem. The temp as well only goes above half way when driving 50 and above....

We shall see