you don't have a leak, your thermostats are weak, they go weak over time. change your main stat and you will get 91c constantly, and less fuel consumption. Trust me.

The new thermostat will hold 90C+ for 2 years at least. I can't tell if your egr needs changing as well yet.

How many miles have the cmax and mondeo done?

 

Not sure why, but my 2004 530d with over 200k miles on It's original thermostat still sits 87-90 degrees all year round, I guess im one of the lucky ones.

 

200k? I find that hard to believe, check what it holds in the highest gear on a flat motorway at 70mph. It could have been regenerating when it was at 87-90c...

are you sure it's never had them changed?

 

Hi E61530DAT, I have just changed mine on my 530d, very easey to do, get the part on ebay. Go to youtube and search on egr thermostat there is a good video on it, sorry have lost the link - good luck

 

Thanks to all of the instructions here and on other places I managed to change the main thermostat in 1 hour!
Now I have a steady 89-90 degrees C.
I only removed the EGR heat exchangerd, the air intake duct and the air pipe between turbo and filter + one screw under the EGR-valve that held the hard plastic water pipe.

I actually did change the EGR-thermostat too at en earlier time as it was easier but that did only raise the temp marginally so I new the main thermostat was bad too.

Thanks everyone!

PS. This work was done on my 2007 525DA LCI with the 3,0L engine.

 

2005 525d (2500cc) running at 69-70C, EGR done (the cheap and easy one), no real surprise but the car has only showed a small increase in running temperature at 75c. Main/waterpump thermostat to do next.


It's ridiculous to not have a temperature gauge on the dashboard. I'd be interested to know when this decision was made within BMW as my my 2002 330i E46 had a temp gauge and an electronic thermostat that generated a fault code when it failed, but the E61 has no tell tale symptoms other than hacking into the dashboard readout!

 

it has taken me 235 posts to see a quote for the 535d , my eyes are sore but im now happy im on the right track .
thankyou Mini Me for this great thread , it looks like it has been going for a few years now , ive replaced the egr stat without any real change , it looks like the main stat will be replaced next , halliwell jones BMW warrington have quoted me nearlly £60 for the part , im tempted to have a go myself ,

Thanks again


2005 e61 535d sport 115K miles , running temp 60 to 72 degrees , just over 20mpg and a range of approx 400 miles full tank , ill be interested to see the difference when i change the main thermostat .

 

I did it on my 535d as well, both of them, but unfortunately didn't help.
I heard, there is third thermostat in the Gearbox oil cooler, price about £180.

 

Main stat now fitted , engine temp is running upto 93 degrees and my mpg has improved alot , much more noticible on the motorway .. ive filled the tank up and ill update when I next fill up :-) . Running temp was at a max of 71 degrees before , im amazed at the difference of 20 degrees on the mpg tbh :-)

 

Was about to have both EGR and main thermostat done. Took it for drive. Within 15 mins temps were above 80 then went to 97 max.
However after motorway driving temps dipped below 90 around 88. Seems while car is in slow traffic temps can reach above 90 sometimes 96/97 but remain below 90 around high 80s when driving .. Sometimes 82.
Does this mean the thermostats are fine and do not need replacing or should the temps always stay above 90. The temps go down just below 90 to 82-85 when driving slow roads but creep up when stationary.