Need straight answer plz

[ADEN]

If the system is not pressurized replace cap rings with new ones and test, also check expansion tank neck seat for cracks.
i believe the problem is with the expansion tank.

[ADEN]

I've searched alot but i got confused and couldn't get a straight answer to my budget m50 swab project.

I have a :
1- m52 2.8l block from 728i (oil pan same as m52 e34 suitable for...