[Apples12]

Hi,
I've been monitoring the coolant temperature in my 520d for a few days, no matter how hard i push the car, in excess of 70mph i cannot get the coolant temperature to exceed 88degrees c.

is this normal? I would have expected at least some sort of increase whilst the car was being really really pushed, but nothing!

wondering if I ought to change the coolant temperature sensor

thanks

[jmmdm2]

I recall reading the BMW sets the cooling system to run the engine cooler the harder it's pushed (relative to operating temp). Lean cruise under light throttle typically runs hotter for better fuel economy, run leaner = run hotter. This is all gasoline related though so not sure how the diesel motor cooling system relates.

[tacos3]

How do you monitor coolant temp? All I have is Fuel level and Oil temp.

[Apples12]

You can enter the diagnostic mode on the cluster (I have the 6wb panel, may be different on others)

So I shouldn't be worried it temp not going above 88?

I remember in my golf when the temperature wouldn't go above 78 it turned out to be a faulty temperature sendor, made a massive difference in fuel economy too

[HighlandPete]

Originally Posted by jmmdm2

I recall reading the BMW sets the cooling system to run the engine cooler the harder it's pushed (relative to operating temp). Lean cruise under light throttle typically runs hotter for better fuel economy, run leaner = run hotter. This is all gasoline related though so not sure how the diesel motor cooling system relates.

Diesel engines run a fixed range thermostat, not the map thermostat like the gasoline engines.

88C is the opening temperature for the diesel thermostat. Running ~88C is right on the money, if the cooling system is efficient.

[HighlandPete]

Originally Posted by Apples12

You can enter the diagnostic mode on the cluster (I have the 6wb panel, may be different on others)

So I shouldn't be worried it temp not going above 88?

I remember in my golf when the temperature wouldn't go above 78 it turned out to be a faulty temperature sendor, made a massive difference in fuel economy too

You mean the thermostat. BTW, 88C is the rating for the thermostat in the diesel.