Hi,

My temperature gauge seems fluctuate more than I'd expect.

Temperature gauge climbs to near mid point, then drops to near bottom then climbs again. On longer journeys it reaches mid point and usually stays there.

I say usually as there was a time if felt a hesitation on the motorway and temp gauge dropped off the bottom before climbing again - I think that may have been a dpf regen kicking in, thermostat opening and cold coolant going past temp sensor. ??

I appreciate that cars don't operate at a constant temperature and the gauge seems to be following as if the thermostat is opening but other cars I've used the temp gauge climbs to mid-point and stays there, it doesn't move about.

Is this fluctuating temperature gauge common and/or anything to worry about? Issue with temperature gauge or thermostat?

Also worth saying it doesn't overheat - at least the temp gauge doesn't go above mid-way.

Many thanks for ay help.

Consider changing out the sensor easy job, once up to temp it "should" stay there unless it overheats, could even be a loose connection between the sensor and the rest of the loom.

2 hours ago, NathanSaul said:

but other cars I've used the temp gauge climbs to mid-point and stays there, it doesn't move about.

but are the other cars diesel ?

Your typical modern diesel engine takes forever to fully warm up, and if you have the heater on in the car that also effects the temperature gauge slightly. As long as it doesn't overheat I'd not worry.

I have the same car and engine and it's totally normal. I drive 20 miles to work and it's about 14 miles in before the gauge will sit in the middle. 

As a comparison, my petrol car gets 'up to temperature' after about a mile, and stays there through 'traffic' or a 50 mile motorway run...

As a comparison my electric car gets' up to temperature ' after??? Oh, hang on . I haven't got a temp gauge. 🤣🤣🤣

3 hours ago, iantt said:

my electric car gets' up to temperature ' after???

If it ever does get 'up to temperature' you'll not need a gauge to tell you it's overheating 🤣

Thanks for the replies. Had diesels before, 2 k9k1.5dci renaults and a old pug 306 - although that didn't have a temp gauge, just a light that came on if it was hot - which was pretty often, ha.

I was more interested in the jumping about, first 10min climbs to near mid-point (I guess to a temp that triggers the thermostat to be opened) and then drops quickly to near bottom before climbing again, rather than the time it took to get to the mid-point but going off above I guess it's okay, may look into temp sensor.

Thanks again

26 minutes ago, NathanSaul said:

Thanks for the replies. Had diesels before, 2 k9k1.5dci renaults and a old pug 306 - although that didn't have a temp gauge, just a light that came on if it was hot - which was pretty often, ha.

I was more interested in the jumping about, first 10min climbs to near mid-point (I guess to a temp that triggers the thermostat to be opened) and then drops quickly to near bottom before climbing again, rather than the time it took to get to the mid-point but going off above I guess it's okay, may look into temp sensor.

Thanks again

That must have been an XUD 306?  The HDi's had a temp gauge, but rarely passed 75c as they're common rail.  XUD's were IDI, using pre-cups, which creates a lot of heat in the cylinder head and gets passed to the coolant.  (HGF wasn't uncommon on them for that reason)

The HDi's were so thermally efficient they had to be fitted with an electric coolant heater (4 glowplugs in a pipe) otherwise the cabin would never have warmed up!

 

Back to the Focus...I think you'd be better off replacing the thermostat than the temp sensor.

Aye, it was an XUD non turbo, 0-60 if you were lucky - I dont think mine overheated due to it being a XUD - more linked to it being an old, sh*tbox first car 😉 

Ta, will look into it.

11 minutes ago, NathanSaul said:

Aye, it was an XUD non turbo, 0-60 if you were lucky - I dont think mine overheated due to it being a XUD - more linked to it being an old, sh*tbox first car 😉 

Ta, will look into it.

Non turbo diesel...  

If you want a chuckle, I briefly owned a 106 TUD and recorded a 30-70 of about 15 seconds on that.

 

 

On 3/9/2024 at 9:30 AM, NathanSaul said:

Hi,

My temperature gauge seems fluctuate more than I'd expect.

Temperature gauge climbs to near mid point, then drops to near bottom then climbs again. On longer journeys it reaches mid point and usually stays there.

I say usually as there was a time if felt a hesitation on the motorway and temp gauge dropped off the bottom before climbing again - I think that may have been a dpf regen kicking in, thermostat opening and cold coolant going past temp sensor. ??

I appreciate that cars don't operate at a constant temperature and the gauge seems to be following as if the thermostat is opening but other cars I've used the temp gauge climbs to mid-point and stays there, it doesn't move about.

Is this fluctuating temperature gauge common and/or anything to worry about? Issue with temperature gauge or thermostat?

Also worth saying it doesn't overheat - at least the temp gauge doesn't go above mid-way.

Many thanks for ay help.

I had the same and found that uf I put the air con on for 20 mins it stopped doing the fluctuations in the winter .I found out as the air-conditioning was on all summer and was the only thing I could think that I changed in the winter not using it .so turned it on to see and resumed to normal temperature on the gauge for the winter. Hope this might help somebody else although might not be your issue but worth a try 

12 minutes ago, johnpaul54 said:

... uf I put the air con on for 20 mins it stopped doing the fluctuations in the winter...

I'd be shocked if the 2 were connected. Your A/C is a separate sealed system, wouldn't impact any other system in the car.

Doesn't the radiator fan run continuously when the aircon is on? If so that might have some effect.

2 minutes ago, mjt said:

Doesn't the radiator fan run continuously when the aircon is on? If so that might have some effect.

Interesting, my A/C hasn't been turned off in over 5 years, but my radiator fan certainly doesn't run full time?

Well, I must admit I wasn't sure about that which is why I phrased it as a question.

It must depend on each car and the individual fan setup.  I thought the slow fan ran all the time with AC on on most cars with a two-speed fan, but perhaps not.  (In fairness, I only ever use it in summer when the fan will be needed to cool the condenser, so that may have altered my perception)

The AC pump does put extra load on the engine though, and the heat from the condenser will reduce the efficiency of the coolant radiator behind it, both of which meaning the engine can retain heat better with AC on.