e12m535i

June, July, August 2004
Well, unfortunately there’s a big update that I’ve been meaning to do for a while. In late June, I went for a drive in the car and when I returned home after giving it a fun thrashing, I was leaking oil down the driveway. Not small drips either. The low oil pressure light never came on though so I can safely say nothing catostrophic happened. I haven’t found out the culprit for sure, but I think possibly a leaking rear main seal or something on the head. Those are my guesses so far.

As I updated earlier on the car’s history, in April of 2004 I had the oil pump replaced and Ben Thongsai who did the work said the motor was on borrowed time. My car has 164K on the odometer, but he and I suspect it may have closer to 200K, probably as a result of a reset to zero odometer when the car was brought into the US in 1985. In particular the rod bearings were junk and he said that was part of the reason for my low oil pressure issues in the summer of 2003. He also noted that the motor had two mismatched connecting rods which were from a later 80’s 3.5l M30 engine. Wonderful…. I had been hoping the car would make it through another summer of some fun, low miles, and cruising but with the oil leak, I said screw-it, let’s do this thing right. It’s rebuild time!

I knew it would take me a while to disassemble everything and get the engine ready to pull. That leaves lots of time to save up some money for this process. A lot of affordability will depend on whether the engine needs new pistons. At a minimum I want to fully balance the bottom end and of course get two matching connecting rods to go with the set. If pistons are in order, I will have to make a determination whether to run stock Mahles (probably oversize) or go aftermarket. Other possible tuning options exist, but of course add cost to the rebuild. The car was already fast to begin with, so it can’t be any worse with a freshly rebuilt motor featuring (of all things!) matching connecting rods.

This section of the writeup will be devoted to the pre-pull process. After the motor is out and the dissassembly of that begins, I’ll take more pictures in another section. The process has been a great learning experience so far and I’ve cataloged every part as I’ve removed it in labeled, ziploc bags. That’s the ONLY way you can do this. Oh, and lots of pictures help, too. Of note are a few things:

The exhaust removal was not that bad, particularly the exhaust manifold to exhaust bolts, which have an awful reputation for rust. A ton of WD40 and letting them sit for 24 hours rendered them helpless to some modest torque with a socket wrench.
I sure wish I’d just drained the coolant first off rather than having small drips as I went along. The bolt was obscured by the exhaust so I decided to leave it. Consequently anytime the car’s pitch changed (or the engine position changed during the tranny removal) some coolant dripped out on the floor. The one 19mm bolt is towards the back of the block, passenger-side, underneath the exhaust manifold. Be prepared with a big bucket (like 5 gallon) to catch it all.
The driveshaft removal was a pain as even with the center bearing support removed, the universal joint didn’t want to allow the shaft to pop out of the guibo. Finally with some gentle but firm action with a prybar on the guibo the driveshaft popped out.
The tranny removal wasn’t that bad as long as you remove the bell housing as well. I wanted to remove the tranny alone from the bellhousing, but the top 19mm nuts holding the tranny on were designed to fit in a location engineered by satan. The casting of the tranny interfers with a socket, so you can’t get them off that way. Even a 12 point won’t fit on enough to grab. The bolts are too close to the body of the tranny to have a box-end wrench fit either. And an open-end wrench will do no good as the transmission tunnel doesn’t give you enough room to work!! Supposedly an S-shaped open-end wrench will do it, but screw that. Remove the bell housing bolts, which are I think 3 or 4 13mm and 3 17mm’s. Easy, easy, easy aside from the tugging and weight of the tranny to move around. I’m glad I didn’t try my half-baked idea to lay underneath it instead of using a jack. And to do it by myself. Duh. My neighbor who used to be an auto mechanic helped me pull the tranny with both of us tugging and the jack supporting it. We gently brought it to the ground without issue.
After telling my neighbor how I was going to leave the tranny fluid in since it wasn’t getting rebuilt or anything, I stupidly turned the tranny over to remove the crossbrace bolt and fluid slowly poured onto the work bench from some kind of small seep hole on the top of the tranny. As long as the tranny isn’t placed in a dumbass position (i.e. upside down) it won’t leak. I don’t know the purpose of that hole, but it screwed me out of a 1/4 quart of Redline MTL.