I bought all the major engine parts from a major parts retailer that offers a lifetime warranty on their parts. This really came in handy because the 4.4 N62 I originally installed had undiagnosed cylinder wall damage. After over 1,000 miles and countless steps diagnosing and ruling out other causes of perpetual smoking I was experiencing, a borescope revealed the cylinder wall damage and a 4.8 N62 was sourced to replace the 4.4.
An overview of the maintenance performed is as follows: upgraded Elring valve stem seals, APA/URO coolant transfer pipe, APA/URO viton alternator bracket gasket, every engine gasket, o-ring and seal was replaced with new (sole exceptions being head gaskets and front timing cover gasket), new coils, spark plugs and fuel injectors were installed as well as a new clutch kit and flywheel.
The most major repair was the valve stem seals, they make a special tool for this engine that allows you to replace these with the heads in place.
The spring is compressed, follower removed, keepers removed, spring is decompressed and removed, new seal installed, then the process is reversed for re-assembly. I have an in-depth guide on this process HERE for anyone looking to do this job themselves, it documents some tricks I've learned after doing this on multiple N62's.
The exhaust side is easy, but the intake side does get a little more difficult as you are fishing the tool between the intake cam and eccentric camshaft.
Coolant pipe installed - this is a common issue on the N62, and the factory component requires removing the front timing cover to replace it. There are several aftermarket solutions for this to simplify replacement, but in my opinion the best is this APA/URO collapsible coolant pipe. You cut the old pipe out, remove the old seals and install this pipe in it's collapsed form, then you expand it out into position and then use the lock rings to keep it in it's extended position. It works very well.
Upper oil pan gasket installed after cleaning the mating surface
Oil filter housing gasket is new.
On the 4.4 I used the stock lower oil pan gasket, but it developed a small leak. I found this to be a somewhat common problem, though the cause seems to be unknown. I think the gasket is just not a great design.
I noted that on RealOEM it says to "use with Loctite 5970" although the TIS isntrutions from BMW don't say anything about this.
I went researching what the Loctite 5970 is for and it ends up that on modern BMW engines, they don't use gaskets on oil sumps and differentials and many other locations. They only use a bead of that Loctite 5970 sealant, I decided to try that myself when rebuilding the 4.8.
I applied a ~2mm bead after cleaning both mating surfaces thoroughly.
This is the upgraded URO viton alternator bracket gasket. This is a very common source of leaks on these engines and is very difficult to service with the engine place but the viton seal should prevent it from being a problem.
New oil thermostat o-rings.
New valley pan gasket, water pump with lower temperature thermostat, and coolant tube.
VANOS o-rings.
Upper timing covers.
Even new o-rings for the sensors.
Numerous other small things were done, literally all gaskets/seals were done except the HG/front timing cover.
The only significant change from stock is converting the oil cooler output to AN10 lines.
I did this just to simplify routing the oil cooler which I need to add for the 4.8 as the 4.4 versions did not have an oil cooler. I did also replace the included o-rings with viton o-rings, as the stock ones were pretty thin and seemed pretty insubstantial.
Only other major change from stock was using the earlier style 4.4 continuously variable length intake manifold instead of the two-stage 4.8 intake. Based on comparisons of power differences amongst other N62's this intake makes 5hp and 25 N-m more torque than the two-stage intake.
This is the refreshed 4.8 waiting to go in.
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