Mondeo tdci mk3 temp issue

[Russ 6334]

Hi all

 

my mondeo has always been poor on fuel based on my last heavier estate always returned 56mpg doing short journeys always cold on 30mph roads

 

i now have a low mileage 70k hatchback same age that I religiously drive at 57mph 80 miles a day to work and back and it returns 47mpg!

 

ive noticed that the temp gauge is all over the place and never really gets warm. I just took it out and hammered it for 2-3 miles at 50mph in 3rd gear and once the temp gauge hit the middle I measured the temp with an infra red gun.

rad hose from rad to stat was 75

post stat to heater matrix was 55

oil stat hose was 75

header tank was 34

rad was 65

 

then I drove home in 4/5th around 30mph and when I got home temp gauge was back to the zero on 60

measured same things again

rad hose from rad to stay was 73

post stat to heater matrix was 65

oil stat hose was 65

header tank 32

rad 66

 

and to make it easier to read

75-73

55-65

75-65

34-32

65-66

 

the car gauge is always on cold on the motorway, the minute you hammer it or reach an incline it starts to creep up but soon goes straight back down again

 

ac is never on.

 

have changed the oil stat today and no difference

 

the heater kicks out really hot air

 

what the hell is going on?

 

 

 

[pragmatix]

Temp sender?

[Russ 6334]

33 minutes ago, Russ 6334 said:

Possibly but where is it? And why would it fluctuate like this when the physical temps aren’t?

 

[thanuttiscotsman]

Running cold on the motorway and constant low temperatures. This sounds like a coolant thermostat stuck open to me. Heating probably will be warm as the hose usually comes straight out the engine to the matrix. 

I have a mk3 petrol and I know the thermostats on them are a common problem but not sure if the diesels are the same.