I had a few hours today to finish tearing the 4.4 bottom end down today.
First thing was to label the main caps, rod caps and pistons with a sharpie, which will probably come off while cleaning, but I keep forgetting to get a dye pen. At least I won’t get confused as I pull all the parts out. The tops of the pistons have arrows point towards the fronts and the rods and caps are etched with identical info so matching them back up is tough to screw up. Interesting fact I learned from JimLev over on BimmerForums: the connecting rods and caps are cast as a single piece, and then the caps are broken off the connecting rods, so they really shouldn’t be mixed up.
I also noted the paint dot colors on the crank at each main bearing journal, as these colors help determine the cap side bearing shells to use. Interestingly, I had dots at 4 of 5 journal locations, but not the rearmost journal. No dot.
Once labeled and lots of pics taken, all the caps came off, both from the rods and main bearings. The pistons are easily pushed and then gently tapped out of the top of the block, taking care to be ready to catch them so they don’t land on the floor. One note: pull the oil squirters first as I nicked one with a rod on its way out. These little things are stupidly expensive, so hopefully mine isn’t ruined. I’ll clean them all up and see how it looks.
Once the pistons are out, or at least pushed to the tops of the cylinders, the crank lifts right out.
The thrust bearings on journal 5 keep the fore/aft play within specs and drop out, literally, when the crank is pulled up. I think I’ll likely buy new ones as they seem really important, and mine have 150k miles on them. They come as an upper set (2) and lower set (2), and are cheap. BMW called them “upper guide washers” and they are keyed to fit into the number 5 main bearing cap.
I drained the remains oil from the block and took a better look at it. Time, and a micrometer will tell, but there is no scoring in any of the cylinders, which is a great start.
It all got loaded into the X5 (ironically), and I dropped the block and oil pan off at the machine shop for a good cleaning and to measure the bores, both for diameter and roundness. 93mm is the magic number, but there is a tolerance for that, and for out of roundness.
The oil pan is likely scrap, but I want to hang onto it just in case it works better in the e34 or e36 the motor finds a home in. It’s a long shot because it’s so deep, but my quick take is that the lower sump is located significantly farther back on the x5 than on the 540 (rear wheel drive oil pan. Who knows, it may help clearing a front crossmember, if it can be modified to be more shallow.
The crank and pistons came home to my little shop and the pistons will need a serious cleaning. The crank looks great, and my initial measurements of the journals look spot on, where TIS, says they should be. This is added peace of mind to my earlier adventures with plastiguage, which also showed journal 1 to be exactly within new spec.
Next I’ll clean and measure the pistons, and start ordering rings and upper bearings shells for the connecting rods (I have new lower shells already), and rod bearing shells.