Hey.

Currently in the process of changing thermostats (auto gearbox, 530xd), and I've seen people recommending (and linking to) a dead forum post supposed to contain a guide for an inline thermostat mod for the heat exchanger which is supposedly better and easier than replacing the heat exchanger.
Since all the links I've found through excessive googling and forum lurking, does anyone here have this guide saved or remember how to do it, and if so - which VAG thermostat is needed?
(Link to dead forum post that I keep finding: https://forum.bmw5.co.uk/topic/13244...nger-write-up/ )

Side note:
EGR thermostat has already been swapped. It's now running at 6.4L / 100km or roughly 37 mpg currently on the highway. Stage 2 tune, DPF and cat deleted, and it's only running at 60 degrees celsius. With any luck, it'll be down to 6.0L / 100km or ~39 mpg once it gets back up to operating temperatures.

 

Managed to get a reply and a photo from a member on an M57 group on Facebook.

The thermostat needed is: 4E0121113

This is where the thermostat goes:


And to make things more clear, this is a better view of which coolant pipe to cut and where to place the thermostat:


If anyone has any input, please feel free to share.

 

Thanks for this info! I will be attempting this soon on my 535D as it's taking forever to get up to temp, or it never reaches operating temp. I've already changed the main & EGR thermostats.

Did this mod work well for you? Any installation tips? I'm hoping to just clamp off the hose above & below the new thermostat position to avoid losing coolant.

Tack!

 

Hi! I actually just posted this to save the knowledge since the old forum posts disappeared along with the old forum.

I have only changed my EGR thermostat and did the main thermostat mod (which I have also posted) and it brought the temps up to normal within just a few minutes of driving.

I've heard of people replacing the EGR thermostats with knockoffs, and them breaking after just a couple of hours. And similar stories even with OEM main thermostats.

I would definitely make sure you got an OEM EGR thermostat to begin with (helped a LOT with my MPG), and might as well do the remote main thermostat mod while you're at it too.

I might do this mod this summer just for the peace of mind though!

 

hello wheperroni why have you cut the top pipes and put in another thermostat while others like the topic cut the bottom one and put the thermostat in black plastic?

thank you for your response

 

Hey. These aren't my pictures, I just managed to find them from a facebook group and reuploaded them since the original guide for this mod was deleted.
​

 

I completed this in December, and it works a treat! The car now warms up to a solid 88-92 degrees within about 10-15 minutes of gentle driving (at about 0 degrees outside temp). Fuel economy has definitely improved.

I used a Mahle/Behr "TH 5 80" and 2 hose clamps.

The process was simple, much easier than the EGR or main thermostat:

• Remove the slam panel & electric fan for access
• Put a big tray under the car to catch any lost coolant
• Clamp the vertical hose above & below where the thermostat will go
• Cut a section of the hose (I used a PVC pipe cutter)
• Slide on each hose clamp before forcing the thermostat into the hose (not easy), tighten clamps
• Top off the coolant reservoir (not much was lost)

I'd recommend doing this if you're replacing the main & egr thermostats, as half the job is getting access.

Big pics...


Fan removed


Hoses clamped (masking tape to show position of tstat)



Done!