So got my car back and on a 5 mile trip home the car easily hit 90 degrees and didn't go below 89 or above 91. Very pleased to say the least. I'll be doing a test like above tomorrow morning and will post results as soon as I can:

The thermostat was broken and it was only luck that a saw a different service advisor than the one who fobbed me off. I felt going over to the idiot and saying I told you so and you don't know shit but I didn't because I want to keep relations good with my local dealer. If anything this has helped me became a familiar face in the dealership and I am sure I'll get treated better from now on (especially as they think I know what I am talking about).

Just for reference my car is a 2006 520d - the technican's response to this thread when he wouldnt accept there was a problem was that my car was not the same engine as other cars in this thread.

 

Hi Jas.

Great results posted there.

I'm presuming your car is under warranty the way you seem to refer?

If not what was the final bill?

I just changed my EGR thermostat and the car runs around 85c like yours.

I'm not too worried and will keep an eye on any deterioration. For info, my 2 year old works 530d and DMS's 535d both run at 86C.
Just odd they should both run at that temp.

Neil.D

 

I have BMW insured warranty with a £250 excess.

The main stat was changed as a goodwill because I raised the issue whilst under the three year warranty and I had a good service advisor.

I did check with RA Engineering in Reading and he reckons the main stay would be an hour to two hours labour (£58 + vat per hour) plus parts (which should be about £50 all in)

 

The EGR stat is the same on almost all BMW diesel engines, I bet the main stat is pretty common too. That means the fault will be across almost all BMW diesels.....

What I have noticed is that these thermostats do age. They start at 92C then slowly creep down after a year or so. I suspect you're OK down to about 85C then you really ought to change it.

And it's the main stat that is usually the biggest culprit, the EGR stat can be the cause but generally isn't the main problem.

 

It's true. The E39 M5 also has thermostat probelms too. They should run at 78c but using the hidden menu this often reveals the actual temperature.

 

Main stat now replaced as well and the car gets to 90 and stays there at a minimum. Interesting to watch the temp climb to 95 going up a long hill and then drop back to 90 on the level or downhill.

 

Just read everything ! Purchased a 2005 m sport auto E61 6 weeks ago. Getting 20mpg avg not impressed even less when doing A & B roads.
Accessed the coolant temperature menu highest it ever got to was 79c. Printed this thread out and handed to the car dealer. They are now going to look at the car. At first they said 20mpg was about right !!! Just trying to fob me off I think. Will keep you all updated. I think changing both stats is the way to be sure after reading all of this. Anyone on here have same or near similar car pre LCI with MPG results before and after.

 

Another advantage to replacing the thermostats is getting heat much quicker in this cold weather.

 

My 2004 E60 530d stays around 75c also after replacing the EGR thermostat. It does warm up quicker though. I am going to replace the main thermostat also as soon as the weather gets a bit better.
Lately the outside temperatures have been below zero and my milage is getting worse so i hope the main thermostat will fix that. And i have a Check engine light on with a "EGR increased emissions" fault which i hope will be resolved.

 

Interesting to read a real life scenario that matches my own (E61 535D).

My car runs at mid to upper 70's when on load at speed but drops back to low 70's when off load and even upper 60's if moving a bit slower. It'll get to low/mid 80's if stationary in traffic (this I assume to be the radiator fan switch setting) but despite the stat being marked 88 degrees, can I convince my local dealer that there's something not right with it? No luck so far despite pointing them in the direction of this thread in which there are so many owners of different models of E60 / E61 diesel with exactly the same symptoms being cured by replacement of one or both thermostats.

In fact when you dig a little deeper on other forums, you find owners of other BMW models complaining about the same thing. Both thermostats are the same part number for every diesel engine (I've only checked Pre LCI) in the 5 series range so I'd wager that they're also the same components for other 1/3/7 series engines.

So, any recommendations on how to get this part changed under a BMW AUC warranty when the dealer doesn't seem to recognise the fault? When was fault diagnosis reduced to "the lap top says no, ergo nothing's wrong" anyway?

Two attachments show my running temp against another owners with a new stat fitted, it's cut and dried if you ask me!