Engine Application and Installation Questions

[X5 THANKS DAD]

Just picked up a 2011 X5 with the 3.0 N55 gasoline engine. Engine is seized. I have owned three E53s in the past with either bad 3.0s, or a bad transmission. In all three cases, I dropped the entire powertrain out the bottom to the remove the engine or transmission.

For the N70, there does not seem to be a lot on info on the internet as far as which direction to remove the engine. There are a few YouTube videos, with one showing a bottom dropout, and the others showing out-the-top. I have seen forum member BergA's post on taking it out the top. The BMW service information seems to direct you to take it out the transmission first, then remove it from the top. That seems like as much work as just taking it out the bottom. I am equipped with two lifts and two shop cranes, so I can go in either direction. Just would like to know which method members have found easier or quicker.

So, Question 1: What do forum members recommend as far as E70 N55 engine removal-out the top, or drop it out the bottom?

My next item is replacement engine application. I plan on just buying a used engine to install right back in there. For the 2011 model year, there is a split on replacement application-either engines up to a build date of 12/2010, or after one 1/11, and they can only come out of an X5 or X6 with similar build dates. I'm looking to find out members' knowledge on what the difference is between the build dates, and if I go all the way down to a longblock, can it be from other vehicles or model years, or do strictly pay attention to the before/after build dates. (Mine happens to need the 12/10 or earlier application.)

So, Questions 2a and 2b: (a) For my 2011 E70 E55 replacement engine, what is the difference between the before/after 12/10 build date and, 2(b) can I use a 3.0 gasoline longblock out of other platforms or model years?

Your guidance and experience is very much appreciated.