All the parts finally showed up so I spent the last two days after getting home from work replacing the large coolant pipe. I would have done the small pipe even thought it wasn't leaking, but new versions are no longer available. I robbed the pipes from my old motor and thought I cleaned them up well enough, but something caused the large pipe to leak. Fortunately the small pipe wasn't leaking. The o-rings looked fine, but there was a decent amount of crud around the joint to the rear manifold.

I opted to do the job via the rear manifold. I had reused that part too and wanted to make sure that I hadn't missed something like a burr, or some crap in the o-ring groove. Getting it off wasn't terrible after pulling the cowl and intake, but getting the gasket pieces off was a pain. I had to use a scrapper and then go at the mating surfaces with 800 grit wet sandpaper. The gasket remnants were completely baked on. I opted for a thin layer of permatex blue on each surface, along with OE gaskets because it was tough to tell if the block surface was completely clean and that I didn't mar it with the scrapper. The car went back together quickly and I filled and bled it fine with no static leaks appearing.

However, when I went to start it I was rewarded with multiple misfires. I had replaced the coils while I had it apart so I rechecked that all the connections were secure. My foxwell was telling me initially that I had "multiple misfires", and then separate codes for misfires on 1 and 5. After checking general integrity the motor ran great for a few seconds, then started missing again. Codes this time for "multiple misfires" and misfire on cylinder 1. It sounded better than it did initially, but definitively wasn't happy.

New plugs today (which I should have done initially) and I'll swap coils to begin troubleshooting in earnest. In the back of my mind is a fear that I've got a shorted/broken wire(s) in the engine harness which needs to be removed and folded over to the right side of the engine bay to get the intake out. The harness is getting pretty brittle.

On the plus side, I thought I had a slow rear main leak, but it turns out the silly oil return hose that snakes from the bottom left of the PCV valve, under the coolant pipes and down to the nearly impossible to reach tiny return pipe (to the oil pan), had come off the nipple on the PCV valve and had been slow dripping into the valley. Small victories. This hose is a huge PITA to get attached on both ends, while setting the manifold in place. This time, I threaded a screw into the end that goes to the oil return pipe on the right side of the block, tied some string to it, attached the hose to the PcV nipple and threaded the string down the hose path to the return pipe (which I had to use a mirror to accurately view and thread the string to). Then I very gently pulled the string as I set the intake in place and worked the end of the hose down its correct path to the return pipe. After that it was painful, but not too hard to unscrew the screw and work the hose end over the pipe with the help of a mirror as needed.

I'd rather be working on the differential project, but I need to get the car back up and running. Regardless, I ended up having to order a set of snap ring shims for the diff as the OE shims were clearly too big to work. The new diff or the new bearings (or both) are likely a fraction of a MM to large. I've never put a diff together, but I'm learning that they work on some pretty tight tolerances.

Given an upcoming painful work schedule starting tomorrow, I will likely turn the X over to my indy to sort out if I can't find a smoking gun today for the misfire project.

__________________
Current
Original owner 2002 E53 X5 4.4i to 4.6i swap
2026 G80 M3 6 spd
2025 G06 X5 50e
Former
1972 Audi Fox
1986 Saab 900S
1996 BMW Z3
1998 BMW E36 M3 Sedan
2004 BMW E46 M3
2006 Audi A3 Quatro
1993 Mopar 318 Jeep Grand Cherokee
2015 V6 Jeep Grand Cherokee