TD4 Temperature Guage

Hi,

During the course of this year i've had my thermostat replaced, and more recently my expansion tank and cap as well as radiator.

Everything has been behaving perfectly, temp gauge always sits half way with no movement and lots of hot air.

Yesterday night it was -1 and i was leaving a friends at 1am, the car started from cold and i had to drive fast (was following a friend with a heavy right foot) and up a winding hill (1.5km maybe?). The temp gauge got up to halfway VERY quickly...once we crested the hill, there was a long downhill - on this the temp gauge seemed to drop enough for the eye to notice, but not right down (sat about 15degrees below half?). Even though i carried on going downhill quickly but not under much engine power it then levelled again and stayed level all the way home no matter what - did this in the space of a couple of kms i think.

What could cause that dip? Is it because i heated the car up so quickly, the thermostat opened quickly and a lot of cold water from the radiator joined the circulation?

Is it an airlock? (not sure the garage bled the system properly since radiator change a few weeks ago - but not had other problems)

Surely its not the thermostat again....after 8 months....?

no it like mine its the thermostat did you have a OEM one fitted

I think that you've answered your own question.

Mine would behave like that too given the circumstances you quote.

It wouldn't do any harm to check the bleed-screw immediately after a cold start though.

When I changed the anti-freeze I bled it according to the book, but thought I'd check after a day or two - there was a short burst of air so I checked for a further four morning until I was sure that all was gone.

Make sure you have the heater temp set to max before you start the engine, and only open the screw a couple of turns (you can use a small coin) as the little rascals have a habit of jumping out of your fingers and disappear forever into the never-never land at the back of the engine.

Singvogel.

Thanks - i'll give it a bleed tomorrow. I just never noticed it doing that before - that's the thing though - when i first got the car new i didn't notice anything....then i found out it had personality (quirks) and became a hobby (spend weekends figuring out what parts need to be repaired or replaced)