When I left for work last Friday it seemed that I had fixed the coolant pipe leak with a new pipe and O-rings all around, and a re-seal of the rear coolant manifold. The large pipe is available new so I went with that, but the small one is not any longer so I cleaned the old one up and used it again. My big problem was I was after putting it all back together again, and with new Bosh coils I getting multiple misfires on several cylinders, which eventually settled down to just a misfire code on number 1. Swapping the coils with 5 didn't change the location.

Back from work last night and after checking under the car (dry, happily) I went to limp the car onto the road for the tow to my Indy shop and she fired right up and ran strong. I drove it around for 5 minutes, cleared the codes and the motor sounded strong none returned. My fear was that I broke a wire in the harness when I peeled it off the motor and laid it off to the right side of the engine bay. The insulation and wires are quite brittle at this point. But now my working theory is that I got water into the harness boxes and or other critical point(s) during a heavy rainstorm last week while the motor was apart. The cowl was off and I found some water in the valley the next morning and despite a thorough vacuum followed by a compressed air blow out, I suspect some remained in the harness.

She's still headed out to my indy today under her own power since I have an appointment I don't want to waste. In her near future are new Bilstein B4 struts, strut bearings, etc. to replace the OE struts that are shot, a vacuum bleed of the coolant system, a new throttle plug wired in, maybe the new LSD diff installed if I can get it together while the car is with him, and I'll get him to put all the ridiculously challenging injector clips on. I found all 8 of mine on backwards when I put the harness back on. I reused my OE harness when I did the motor swap and didn't notice they were installed backwards. The new motor ran great for 2 years, but clearly the plugs were not 100% seated.

In other news, the LSD swap came to a halt because the new diff wouldn't fit in the housing with the OE snap ring shims. I suspect the taper bearings I bought are ever so slightly different. I am new to working on diffs, but I've learned that the shim tolerances are measured in tenths and even hundredths of MMs. Fortunately I found a package of 10, 188K "medium" diff snap ring shims from Racing Diffs (in Serbia I think) that run incrementally from 3 to 4 mm and which will arrive tomorrow. Hopefully some combo of these shims will give the proper backlash. The OE shims will fit but are way too tight and jam the crown gear against the pinion, not allowing the diff to turn at all. My OE snap ring shims are marked 3.64 on the left and 4.0 on the right. I suspect I need maybe a 3.5 or 3.4 on the left side.

If I can get the thing together, and with the proper backlash while my indy still has the X5 this week, I'll take it out to him to install along with the new driveshaft CV joint I bought and center bearing. I've been getting a definite 'ping' sound when I select drive and reverse which could be quite a few things, but I'm hopeful that the new diff, center bearing and CV joint will take care of it.

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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