[bennye90]

Hello everyone,

Here is my DIY for the heater return line within the E9X platform. The heater return line connects to the expansion tank, thermostat, heat exchanger and transmission. It is the longest line running along the width of the vehicle in between the subframe and the radiator.

PART IS INDICATED AS NUMBER 21 ON REALOEM DIAGRAM

*Note: This part is different between each vehicle model (i.e. 328/335) and will also be different for xdrive and no xdrive as well as automatic and manual transmission.

THE PROCESS IS THE SAME BETWEEN ALL PLATFORMS BUT PART NUMBERS ARE DIFFERENT.

**I AM NOT RESPONSIBLE FOR ANY DAMAGES/INJURIES THAT MAY HAPPEN. ALWAYS WORK ON YOUR CAR IN A SAFE MANNER**

Tools needed:
- T20 Torx
- 10mm socket
- 10mm short wrench
- Various socket extensions
- Screw Driver
- Drain Pan
- BMW Coolant
- A second person will definitely help

Preparing car for work:
Step 1: Jack up the front of the car onto jack stands (DIY in forum)
Step 2: Remove the belly pan (DIY in forum)
Step 3: Working from the top of the car, remove the intake duct with the 2 T20 torx screws in the front
Step 4: Remove the intake box with the 2 10mm bolts
Step 5: Loosen the intake boot clamp with a screw driver and disconnect the MAF sensor
Step 6: Remove the intake box

Coolant work:
Step 7: Drain the radiator by removing the blue radiator screw
Step 8: There are three 10mm hex bolts holding this part to the subframe of the car. 2 can be accessed from the bottom of the car and the 3rd one is in a really tight space beside the power steering pump (below the intake)
Step 9: Remove the two 10mm hex bolts from the bottom of the subframe
Step 10: Remove the 3rd 10mm hex bolt near the power steering pump/lines. I was able to remove it with a short wrench and patience - working from the top of the car. It is a tight squeeze for someone with bigger hands so it may be easier to disconnect the power steering pump lines.
Step 11: The part can be easily seen as the only coolant line running the width of the car and is connected to the expansion tank > thermostat > heat exchanger > transmission line. To remove these hoses, the BMW metal clip will need to be pulled up by a screw driver. It is okay if the clip completely comes off, it will be used for your new part
Step 12: Remove the hose form the bottom of the expansion tank - work can be done from the top
Step 13: Remove the hose from the thermostat, this one is a hard one to separate so take your time - work can be done from the top and bottom
Step 14: Remove the hose from the heat exchanger - work can be done from the bottom
Step 15: Remove the hose from the transmission line - work can be done from the top near the intake
Step 16: Remove the part and take all the hose clips off and insert onto your new replacement part
Step 17: Assemble in reverse order, make sure all the clips on the new part are inserted all the way.. when reinserting the hoses, the part should click into place (audible click)

Coolant fill + bleed:
Step 18: Fill your coolant and look for any leaks while doing the bleed test (DIY on forums)

[Dobrin]

I know this is an old post, but thanks - it is very helpful!
As you said, all these lines have different part numbers between the various models. But do you know if they are interchangeable? I am asking, because the one for my car, part # 17127544557 is no longer available at any retailer (it is for the manual xDrive 335).