Opinion on coolant temperature

[aslan]

Hello

This is a 2.5T model. The shop replaced the thermostat recently with a Volvo one as it was leaking.

I checked the coolant temperature today using the torque app and it showed the temp ranging from 94 to 99C. All this while since I had the car the temp has been around 89-90C with little fluctuation. And my records goes back to 2015.

I pointed this out to the shop and he said according to spec the coolant is supposed to run at a higher temp and it is permissible for it to reach 104C. In a way saying my coolant was running at a sub-optimal operating temperature all this while.

Thought I'd get a second opinion from the folks here.

Thanks

[S60D5-185]

What is the temperature gauge on the dashboard telling you?

I realise that it will not be as accurate as having the temperature measured precisely BUT If it is sitting in the middle when the engine is warmed through, you may well be overthinking this.

[aslan]

Originally Posted by S60D5-185

What is the temperature gauge on the dashboard telling you?

Slightly to the left of 12 0'clock

Thanks for the reassurance. Sometimes not knowing is better

But on another note, in addition to the coolant running hotter, I also noticed my LTFT is now at -6.0 to -7.0. The LTFT previously was around -3.0. Not sure why it has changed and if it has any relationship to the current coolant temp

[SwissXC90]

Petrol engines run hotter than diesels.
My 1997 V8 petrol BMW ran at 104°C, constantly.

Many internet resources say 90 to 104 °C is normal temperature range for a petrol engine

I would pick 89 to 90 as being on the cool side with 94-99 being normal
Man cars have the mid range of the temp gauge at 90 to 100 °C

[XJSDriver]

Diesel more efficient than petrol so run cooler.

[oragex]

90-95C-100C is the perfect range. At idle it should stay close to 90C, when accelerating it will climb to 95C, and when driving harder or in hot summer days it will reach 100-105C at which the cooling fan will kick in. The thermostat opens gradually from 90-91C to about 95C (fully open).

Possible with your older thermostat the coolant was sitting around 90C because old thermostats are slightly stuck open causing continuous coolant flow to the radiator, which keeps the coolant temperature lower - this is detrimental to proper gas mixture combustion and mileage.

[aslan]

Thanks very much to all for clearing that up. My volvos have been running cold all this while

Would a cooler engine cause more carbon buildup in the combustion chamber?

Any other long term ill effects on the engine? Besides the higher fuel mileage.

[SwissXC90]

Originally Posted by aslan

Thanks very much to all for clearing that up. My volvos have been running cold all this while

Would a cooler engine cause more carbon buildup in the combustion chamber?

Any other long term ill effects on the engine? Besides the higher fuel mileage.

Engines running a lower than optimal operating temperature are less fuel efficient, and produce more emissions as the fuel is not burnt as efficiently as it could be.

The engine will now run better, longer.

The ill effects were occurring in your previous condition with a cooler engine than it should be.

So everything should improve for you

[aslan]

Originally Posted by oragex

Possible with your older thermostat the coolant was sitting around 90C because old thermostats are slightly stuck open causing continuous coolant flow to the radiator, which keeps the coolant temperature lower -

Makes sense. All my previous volvos were used car bought at around 5 years old with about 100k km on it. So I never had a 'new' volvo with a 'new' thermostat. And I sold those cars with the original 'faulty' thermostats haha ...

Never had to replace them as wasn't leaking and I thought the temp I was seeing was good

Thanks