What is acceptable leak down on N62 ?
 

Hi guys, I'm still in the process of changing out the motor in my X5. I finally got all the new parts and was going to start changing them over on Sunday. I decided to run a leak down test on the replacement motor and got some high numbers. Since I'm no expert on this; I'm hoping someone here can tell me what is acceptable for leak down. I ran the check in firing order; and triple checked the ones with bad readings. With the gauge I used; the higher the number the worse the leak down. The air is coming out the exhaust ports. so the problem is valves not fully seating. I can wiggle rockers when at TDC so they aren't holding valves open.
Cylinder 1) 50-55
cylinder 5) 5-10
cylinder 4) 35-40
cylinder 8) 10-15
cylinder 6) 5-10
cylinder 3) 5-10
cylinder 7) 65-70
cylinder 2) 50-55
I would hate to go through all the work of putting this motor in and have it run like crap and give me mis fire codes...Barry

Leak tests are usually used to determine the cause of a low compression reading on a standard compression test.

Perform a compression test. Start the engine, allow to get to operating temperature. While engine is running, remove the fuel pump fuse and allow to die from fuel starvation. Turn off ignition.
Remove all spark plugs. One cylinder at a time, crank engine over, throttle open, allow up to 10 compression strokes or until the gauge stops moving up.

Post your results

Great advice but all rather hard to do on an engine that is not (yet) in a car... ;)

I appreciate what you are trying to do, but on a cold, dry engine, your readings are going to misleading. I agree with
aureliusmax, but sucks that you are trying to be proactive while engine is out of car. But metal expands when heated, things start to move around, etc when it is running. If it was me, I would install, get running and see what happens. The downside is that if it doesn't run right, yes you are pulling the heads to do a valve job. And lets not even talk about doing compression/leak down with the motor in the car! PIA. I will say, once you have removed and installed one of these motors once, it isn't that big of a deal if you want to remove it again to do head work.
What is history of this engine?
I just replaced the N62 in my E53. Came out of a running 7 series, was supposedly perfect. I have a knocking/valve train noise on one side that is driving me nuts. But, I had to put it in to find out. Keep us posted.

You can perform a compression test with the engine on a stand, and apply electrical power to the starter. Some engines have the starter on the engine block (GM style V8s) and others have them bolted on the transmission side. You may need to also have the transmission bell housing installed to the engine block to install the starter.

The reading on the gauge won't be the same as a warmed up engine, it will be less.
What you would look for is minimum allowable difference between cylinders, and minimum compression for ignition.

You are between a rock and a hard place. I wouldn't want to drop the engine in and see what happens either.

You can do a ballpark compression test by just rotating the engine, While the compression will be different than the engine at operating temp you can see if there is a significant difference, more than 10%, from cylinder to cylinder. That is primarily the telltale information you need to know to start troubleshooting for a problem.

Unless you can borrow a fully functional motor stand it is probably easier to drop the engine in and hook up as little as possible to get it running or take the engine to an independent shop that specializes in BMWs to do a post purchase inspection.

I don't think it was actually done in the following recent thread, but starting at post #21, here,

https://xoutpost.com/1175403-post21.html

there was some discussion about rigging up the starter without a full install. There, the M54 engine was in the car following a rear main seal install, and he wanted to start and run the engine without the transmission attached, to confirm the RMS was not leaking.

Discussion of rigging up a bracket to mount the starter, etc. May be helpful in letting you consistently spin the engine using the starter, with the engine not installed.