I said I'd report back on the MPG change since changing my thermostats:

Car was running 80-85C

Now runs 91-93C

Car 2004 535d touring.

I'd say perhaps a 2-3 MPG improvement, maybe. Difficult to tell and my car computer was out (reading 8% low) so I've corrected that too.

Before on a flat bit of motorway it would show 35.9 MPG (actual 38.8 MPG) at about 70mph, now I think it will report over 40 MPG (just), that's with the revised correction factor. I'm not 100% because I've been averaging the MPG for the whole tank, but I think overall it's a couple of MPG up on where it was before the thermostat change.

 

I have been following this posting for a few weeks now.

I was suffering from slow warm up and a max temp of 82 so I changed the EGR thermostat last weekend. As per others you could blow straight through it.

(I also found out that the two bolts that fix it down to the EGR cooler are not magnetic - it's a sod to get out if you drop the rear one......)

The car nows warms up so much quicker but it still maxs out at 82/83 so it is going to the dealers next week for them to check and hopefully replace the main thermostat under warranty.

The car has gone into DPF cleaning mode twice now in less than 200 miles. The temp then has then gone to over 90 but it then drops back to 82/83.


I also noticed that the auto gearbox is a lot smoother.

Looking ar REALOEM there is an oil cooler for the auto gearbox oil and that this must be picking up heat quicker now. It's hard to tell from the diagrams below to see the real flowpath of the coolant.








Perhaps those members who report poor shifting may have an underlying coolant problem as well.??

Does anyone think that the gearbox will have suffered from having it's oil too cool ?.

 

Same experience here, i had been noticing that it had been taking ages to warm up so after reading this thread i changed the EGR thermostat, which could be blown through. It now warms up much quicker but still only reaches 87C, no matter how far i drive. Looks like the main thermostat is faulty as well.

 

silly question, how do you check the temprature? I assume its not somewhere obvious?

 

It has been stated in earlier replies but I find you can either have the car running or just powered up.

(I have done this whilst in a queue of stionary traffic !)

First press and hold the tacho reset knob down until you get 01.__ __ up in the centre warning area.

Release the knob and you will get B123456 come up where 123456 are your cars specific numbers.

Ignore the first number in the sequence and add up the last 5 . ie if you have B451525 you would have 5+1+5+2+5 = 18.

Press the knob down until it reverts to 01.__ __

Release and press repeatedly until it reaches 19.__ __

Release and wait until it come up with CODE : 0.

Press the knob repeatedly so that it reads CODE : 18 ( or whatever your 5 digit add up to.)

Wait until it reverts to 01.__ __

Just press the knob again to get to 07.__ __

wait and then it will then display the coolant temperature.


It is a bit of a hassle but you will get used to it.

 

thanks, I'll give it a go

 

wee bump I had a similar problem, temp was down arund 80ish. So I replaced the EGR stat and it was a little better, 90 in traffic but once I got speed it dropped to 80 again.

Fitted a new stat yesterday and its rock solid on 90-92 now. Will drop to 88ish if I speed up quickly but gets back to 90-92 in a few seconds. MPG is good and operating temperature is spot on so very happy now. Swap was easy enough (04 525d) took just over an hour.

If I hadnt seen this thread I probably would have thought it was ok.

 

Anyone has a DIY for main thermostat replacement? DIY for transmission heat exchanger replacement would be cool aswell. thanks! car is E61 530DA.

 

Main stat DIY with out pics

https://5series.net/forums/topic/949...1#entry1124246

If you do it please take pics

 

changed EGR thermostat few hrs ago, but not much effect on temps. was 81-83'C before, now 82-85'C. Might be main thermo or then the thermostat in tranny.