Bit of an odd one, but this is my go to place for random thoughts from a variety of inputs. Sorry!

My 2.0L HDi (2005) used to run at 90 degrees. No Question. Winter, Summer, Motorway or stuck in traffic going up hill.

The other day, i noticed it was running at 83 degrees (99% of people would even have noticed i guess)
I mentioned it to the mechanics when it went in for a service, and their thought was:

“whatever it is, it WILL be the Thermostat, and by the time we have diagnosed it youve paid for a ‘stat several times over, they are about a tenner”

The new stat and service didn’t “solve” it (or change anything), but seeing as its not a “problem” they didn’t seem to bothered or inclined to go rummaging around the cooling system

Now i have noticed that sitting in traffic, the temperature rises and rises (as you might expect). according to the garage the fan comes on when it should, so it isn’t a problem.

Except, it never used to do this. It used to sit at 90 degrees irrelevant.

It is Warmer weather i guess at the moment, the rad isnt taking “enough” degrees of temperature off the engine per cycle of coolant, and therefore the temperature can rise when it doesn’t have air flowing over it? In cooler months the rad can keep the coolant level down on its own?

Perhaps ive just answered my own question….

Same engine, same symptoms recently, except my fan comes on for a few seconds then goes off again.

Open up the dial and glue the needle to point at 90. Problem solved.

If no coolant loss and the fan works I wouldn’t be too bothered obviously engines “feel” the temp difference quickly. But that’s what your fans for. Did they also replenish the anti feeze? That will help keep the temp cooler. I wouldn’t worry about it unless it’s using coolant .

Dash temp guages are not known for being acurate. A 7degree difference can be down to guage deciding its having a off day sensor dirty a voltage difference from alternator. Basicaly unless it shoots up into the red dont worry.

Has it been bled completely, these are finicky on bleeding sometimes, bleed point on the thermostat housing and another one near the bulkhead.

Does it have a seperate thermostat for the EGR system? If so it’s worth changing that as well.

Only way a car can run colder than it’s supposed to is if a thermostat is passing when it shouldn’t. Well that or the gauge is wrong. How confident are you it was actually changed? And was it a good part or a cheapie?

Running colder will make it less efficient you notice any drop in mpg?

Ive downloaded an app, I am keeping an eye on the mpg (i know what it should be getting)

They have changed the Stat, its right at the top, blatently brand new.

Running temp for an HDi is actually 83 degrees, so its closer to what it should be now having had a dig in the haynes.

I think you might be right HughStew.#

Cheers all!

I was going to say the 83 deg sounds about right for the 2.0 HDI. I’ve got 2 and the only time they every get up to 90 is when stuck in traffic on a hot day.