Hello! I recently acquired an m54b30 from an 03 530i with 127k miles and plan to swap it into my 325ci.
I just completed my first series of leak down tests today (a total of 5 tests) in an attempt to get a consistent set of results. While doing this little project, I found a few things noteworthy I’d like to share and maybe some of you with more experience can shine some light on this for me.
For context, this motor is currently on an engine stand, and has not been ran in 2 months. Prior to this, the previous owner knew his way around an m54, installing some upgraded parts such as the metal impeller water pump and steel coolant pipe (below the intake manifold) and a few more small improvements to help improve the longevity of his motor (what I’m getting at is it sounds like he took very good care of it) He ended up pulling this m54 to install an m62 v8 in his 530i.
I followed 50skid’s video on YouTube to guide me through this and bought the exact tester he used as well (otc 5609).
My first test results:
Cyl 1: 22psi (78% loss)
Cyl 2: 44
Cyl 3: 71
Cyl 4: 48
Cyl 5: 68
Cyl 6: 99
Of course, these are terrible results and I was concerned right off the rip that I basically had an m54 paperweight with burnt valves. Turns out, I was doing a few things wrong.
Firstly, I had mentioned earlier that this motor had not had its crank rotated in over two months, so there was no oil on the rings or quite frankly anywhere else but the pan to lubricate things to get proper results. (I was unaware of this at the time)
I was instructed to add a small amount of oil to each cylinder and rotate the crank a few dozen times to seal things up. Over the course of 4 more series of tests, the numbers got better and better with my final tests results being as follows:
Cyl 1: 99 psi (1% loss)
Cyl 2: 97 psi
Cyl 3: 98 psi
Cyl 4: 100
Cyl 5: 99
Cyl 6: 100
(I should note, before the final test I poured in a small amount of seafoam in each hole and rotated the crank a few dozen times, and then turned the engine upside down to dump all the excess out of the spark plug holes) those numbers were as shown following that.
However, I did have one notable issue of that’s still rattling in the back of my head. On the first test I did get air blowing out the plug hole from cylinder number 3 (while testing cyl 1) but, after adding the oil, this didn’t happen again for the next 4 sets of tests. Is that something to be concerned about? Or was that just a freak case of air leakage due to lack of lubrication. That location would indicate the head gasket is bad allowing an air leak into the next cylinder over, but if that was the case it should’ve leaked into cylinder number 2 not 3… thoughts on this?
other than that, being said, for a 20 year old motor those numbers are great! But one member of e46 owners group on fb was suspicious those numbers are too good to be true going on to say even freshly rebuilt motors can have 5-10% loss.
Now that I’ve explained my process, and comments I’ve received in regards to my good numbers, my question is: are those numbers to good to be true or is it quite possible this motor is in as good health as I have found?
Thanks for the comments in advance!
