S50 coolant expansion tank to S52 conversion: a parts list and helpful hints

[robb1887]

So some of you have seen it, but this past winter I converted my S52 based US model Mcoupe to fit the S50 expansion tank and wanted to consolidate my experience. Some asked why I would do this when there are other less complicated options, but for my future engine plans and engine compartment layout this was the most preferred method for me. You can decide if this is the path you want to take at your own will.

Disclaimer: This is just how I did it, following in my foot steps is done at your own risk.

Pros:
Highest point in system, a.k.a. self air-bleeding
Moves tank away from hot manifold/head
Tank is much more robust
Removes 4+feet (estimated) of soft hose

Cons:
A lot of relocation of interferences (read: lots of wire slicing)
Labor intensive (read: LOTS of fitting required)
Body and pipe welding required
Deletes TB "heating" lines (if you call this a con)
Deletes SAP (I had this done previously)
Deletes OEM heat shield

Parts list (Full list of my setup, parts below line are cooling overhaul parts versus euro tank required items):
Expansion tank- 17111712641
Expansion tank overflow drain hose- 17222246036
Body bracket 1- 41112491298
Body bracket 2- 17111719190
Body bracket 3- 51712490388
Tank clip- 17111719190
Radiator to tank hose- 17118410193*
Hard pipe to tank hose- 11531405284*
3/4" OD Steel tube (3ft)- Sourced from McMaster-Carr (P/N: 9220K391)
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Heater core valve supply hose- 64218401809
Heater core valve discharge hose- 64218362777
Heater core return hose- 64218401808
Water pump to hard pipe O-rings- 2x 11531703848
Upper rad. hose- 11531708499
Lower rad. hose- 11531436988
88*C thermostat- 11537511580
Thermo. housing gasket- 11531740437
Zionsville S52 (Type 2) aluminum radiator
Lower temp fan switch

Optional: (I used my originals)
Aluminum thermo. housing- 1153722531
Expansion tank cap- 17111742231
Expansion tank plug- 17111719430

Special tools:
3/4" OD tube bender (3" bend radius)
3/4" flaring tool

*Items will require sourcing from outside of the U.S., for whatever reason BMW Germany does not allow sale of these two parts to the U.S.. I sourced mine through a Canadian member.

Photo process with helpful hint captions, sorta a DIY (mix of phone and DSLR shots):

So these two are of the interferences removed, and majority of the cooling parts removed. The fan and heat shield get removed later


Fan removed, some of the heater core hoses still in place for "cleanliness" until the system gets restored


SAP previously lived here, but was removed long ago. OEM heat shield is also removed.


Test fitting the tank


Since I removed the OEM "heat shield" I wrapped my ECU box in Carbon "heat shield", and also ensured the cooling fan worked (my original was dead)


Battery tower and Diag. plug relocated, all wiring was taken from salvage cars at the local yard to keep it as "OEM" as possible


Shots of the hand bent pipe to go around the head. I have a photo of it post welding and paint but its not uploaded yet. I splices the US cooling pipe with the custom bent pipe. The section that is to the left going to the water pump is original and was cut just before the throttle body tie ins. The heater tie in was also taken from the US cooling pipe and cut to be welded into the new custom piping so both connections are OEM. The Euro cooling pipe is just under 3/4"OD which is why I went with 3/4" OD tube. The free end at the tank had a weld bead laid on the end to give the hose clamp something to bite on.


Coil pack plug relocated here you can see the loop near the firewall


New radiator in, new vent pipe in (it will eventually be replaced with steel/SS tube, it is supplied from the OEM as plastic), fan deleted, new upper/lower hoses, thermostat, and fan switch installed


Overall shot of how everything looks now


Two brackets require welding to the body, accomplished by a total of 6 spot welds. I also relocated the Diag. plug and removed the "ground connector" on the tower which will be painted when I can get around to getting some color matched paint until the whole car is reshot. Also seen here the SAP relay is deleted, and the other two that were in the box on the front of the ECU box were relocated inside the ECU box in the spare space.


Diag plug, Battery (+) wires, & relay wiring all required lengthening of various degrees. You can also see the brake line was bent a bit to flow better now that the original heat shield is removed



Side shot, all three "new" brackets can be seen here if you know what you're looking at.


Throttle body cooling line nipples were removed and the new hard pipe does not have the connection for it when remade. Tap in the head I used for a VDO water temp sender or can be plugged.


Temp sender: VDO 0-250* M12-1.5 Sender P/N: A2C59517248-S


If you have any questions I'll answer as best I can and incorporate them above or make a FAQ below.

I personally am very proud of how everything came out. It all works great and from where I wanted to be when I started to where I am is spot on. My goal for this car is all going to a complete Turbo car, so as this may be overkill now (like my tires) I wanted to only have to do it "once". And not rework anything later due to interferences. I still have a few more tricks up my sleeves for the engine bay but as far as the cooling, it has a giant stamp DONE across it.

Happy modding!