Diesel running temp in colder weather

[Split_Pin]

Up until this week my diesel temperature gauge has sat bang on the 9 o'clock however with the recent cold snap I have had the heater on hot and the needle now sits at around 8 o'clock. As soon as I turn the heat down a little it returns to 9 o'clock. Do I need a new thermostat?

[KeithA]

Originally Posted by Split_Pin

Up until this week my diesel temperature gauge has sat bang on the 9 o'clock however with the recent cold snap I have had the heater on hot and the needle now sits at around 8 o'clock. As soon as I turn the heat down a little it returns to 9 o'clock. Do I need a new thermostat?

Yes, or fit an additional stat into the top hose.... Quite an easy job

https://www.dmgrs.co.uk/products/rov...tat-89-degrees

Sent from my Redmi 5 Plus using Tapatalk

[Split_Pin]

Thanks for your help, I have now ordered the one from your link. I thought I might have to do this job sooner or later.

[bl52krz]

It is all according to how far you have driven. If you have only gone about a couple of miles, the diesel being so efficient takes a long while to really warm up. When it has warmed up properly, you can use the heater without the temp gauge dropping .

[trebor]

Use the OBD via the trip switch to check your coolant temperature it will tell you what temp the coolant is getting to and you will then know if you have a problem or not

[kelvo]

Originally Posted by bl52krz

It is all according to how far you have driven. If you have only gone about a couple of miles, the diesel being so efficient takes a long while to really warm up. When it has warmed up properly, you can use the heater without the temp gauge dropping .

Biggest problem with diesels, they naturally run colder than petrol engines

Notice the difference with the works Mondeo I drive in the cold weather, takes almost a couple of miles for the temperature gauge to move off the "cold" mark.

In the old days you put a piece of tin foil or cardboard across the radiator or invest in a radiator blind.

[SD1too]

Originally Posted by kelvo

In the old days you put a piece of tin foil or cardboard across the radiator or invest in a radiator blind.

Yes I remember seeing that too Kelvin when I lived in the north east, usually on buses or HGVs. Of course if the thermostat was doing its job such accessories would be unnecessary unless there was a concern that the inrush of bitterly cold air would freeze the fuel lines.

Any thoughts on that theory?

Simon

[v-man]

Originally Posted by kelvo

In the old days you put a piece of tin foil or cardboard across the radiator.

I have done that on at least two petrol cars I have owned, as it helped to increase the rate at which the engine warmed up on short journeys and so reduced the condensation mayonnaise inside the rocker cover. I was always careful to remove it before longer winter journeys or as the weather warmed up in spring.

[kelvo]

Originally Posted by SD1too

Yes I remember seeing that too Kelvin when I lived in the north east, usually on buses or HGVs. Of course if the thermostat was doing its job such accessories would be unnecessary unless there was a concern that the inrush of bitterly cold air would freeze the fuel lines.

Any thoughts on that theory?

Simon

problem with a bus engine, they are rather large lumps and so take a long time to warm up at the best of times, and with all the cold air passing over the engine it probably over cools it - there was often concern over the bottom part of the radiator freezing as often anti-freeze wasn't used.

I own a bus and I know when driving it in cold weather quite often the radiator will still be cold. I know the thermostats are working correctly but I tend to block the bottom of the grille off and it runs a bit warmer. I do find if I run the heaters before it has fully warmed up then it takes a lot longer to warm up, so this would back up the theory that in very cold weather the engine is losing heat faster than it can generate it.

[bl52krz]

Hi Simon. You are correct, it is not a theory. I have lit many a fire under the fuel tank of a lorry in deepest winter many years ago, to unfreeze the diesel. It turns to a gel below a certain temperature. Now they refine it more during the cracking of diesel from base oil. Also they now put additives in it also to stop it freezing. Ahh the good old days.