[StradaRedlands]

I mentioned this process in the What Did You Do Today thread, but wanted to write up a more informative stand alone DIY post for anyone considering this. This is on a an E90 with a manual transmission, so the coolant pipe needs to be replaced. If you are doing on a car with an automatic, you don't need to swap out pipes, just the hose connecting it to the radiator. Can be very inexpensive if you get used parts, and is incredibly easy minus one small part of it on MT cars (more on that later on!).

If new is how you roll, the full kit can be purchased from FCP for around $800. Probably not worth it, at least it wasn't for me. But I do enjoy poking around my local wrecker, and easily found the oil filter housing, cooler, and cosmetic cover for about $40. You can get them on ebay easily as well. They are on most non-turbo BMW cars from the aughts and early teens. I think anything with an N52 or N20 engine would have them. Mostly E60 530i donors in my local lot. YMMV on that. I think it cost me about $260 with a mixture of new/used parts. You can cut that down significantly by rebuilding the coolant pipe seals rather than getting a new one.



Take the time to pull off the cooler and make sure it isn't pitted/galled. I didn't and had to go back and get a second one. But other than that, they are pretty good used IMO. I bought the rest of the parts new from FCP, including the coolant pipe. You can buy gasket and O-ring to rebuild it, but I figured I'd spring for a new one. I question if that was wise, but it is what it is...



Removing old parts is VERY straightforward:
-Jack up the car, pull the right wheel and fender liner off
-Evacuate the coolant from the expansion tank (about 2L) and remove reservoir
-Evacuate oil in filter housing and set aside
-Remove oil filter housing (three torx bolts) on top of engine
-Remove coolant pipe if it is a manual transmission. Automatic transmission can skip this step! One hose clamp on rubber/water pump side, two small torx on metal/engine side. Catch another liter or so of coolant that drains out from the hose (I toss that coolant as it is pretty contaminated from running through the underside of the car).

Removing coolant pipe bolts from below the car:


Coolant draining from hose before removal:


Installation of the new filter housing is super easy:
-Attach the cooler to the housing with an updated gasket before putting on the car. The three bolts are steel and you can re-use and torque to 16Nm.
-Install oil filter housing with new gasket using three NEW bolts torqued to 22Nm (I guesstimated the short one on the bottom).
-Install the coolant hose to the cooler nub using a hose clamp.

Loose fit:



HARD PART: The coolant pipe is a bitch to install! Should be easy, right! Came off like nothing to it. Well for me it took several hours over two days to finally get it back on. The bottom torx bolt is easy to thread, and the pipe's rubber side slips over the pump easy-peasy. But the top bolt just sucks. The front manifold protrudes over it just enough that you can't line up the bolt well and is easy to cross-thread (steel bolt, aluminum block). Coming up from below creates a really tough angle, and from the top you can't see or get your hands in there. I damaged the threads on the block just a little before calling it quits and pretty much didn't sleep that night stressed out by it.

The next morning I pulled the pipe off, threaded the bottom bolt for a visual guide, and took my time trying to feel the top bolt in correctly. It took another hour plus but I got it going for the dry run. I was on the ground looking up, with my left hand between the control arm and steering rack guiding and supporting the extension, with my right arm holding 24" of 1/4" extension with a U joint and the torx socket above the frame spar and through the wheel well. Incredibly awkward and uncomfortable, but got it threaded! I removed the bolts and loosely installed the pipe hoping for the best. I figured I could at least get it assembled enough to drive to a local mechanic, trailing coolant the entire way! Happily I had cleaned the threads enough and had a good enough of an angle that I got it in! I don't know the torque value, but went with snug.

Took nice break, had more coffee, lots of deep breaths.

Attaching the hose end to the pump, and the long coolant hose to the flange/nub was super easy, so I did that, surveyed my work and starting filling up fluids! Poured the reserved oil back into the filter housing and threw the filter and cap back on. Reinstalled the expansion tank and added the reserved coolant (just changed it a few months ago, so decided to re-use) and topped off with distilled water and bled the system. No leaks so far!

Moment of truth, so I started it up and waited for leaks... all was good!

Finished product:



I've wanted to do this for a while as I live in hot inland Southern California. Temps are ~100-110F for at least three months of the year and it just seems like a good upgrade. Pure BMW from their "nicer" cars that they left off the mass-produced three series. Parts are cheap and readily available to whatever degree you want them to be. And I'm a sucker for Euro or off-menu upgrades.

But that bolt... it's not impossible, and if you have done this and have a better way, please share! But it was scary for a bit there when I didn't know if I had damaged the threads and if I could get it back together. Catastrophe was averted yet again, and car is now at least 3.7% more awesome!

I'm no expert, but am happy to answer questions if you are considering this upgrade. Just don't blame me about that top bolt... you've been warned!

[StradaRedlands]

I just did the upgrade on another car, and wanted to add clarification that all of the above steps are for adding the oil cooler to a car with a manual transmission. If you have an automatic, it's a lot easier as you don't need to swap the metal pipe from the engine. The automatics already have the extra nub that has the line connecting to the bottom of the radiator. You will need to get a new three way connector hose that is specifically for a Z4. It connects to the radiator, engine pipe, and now up to the oil cooler. It is part number 11537526941 which I bought as an aftermarket part from FCP.



They are about $100 from the dealer if you want to go with BMW part.