My Breaker bar is only about 2 feet long.
I was told if I put too much force on it I can mess up the rings.
One thing I noticed is that when I crank on it with the bar I am tightening the nut and I don't want to brake it off or something
Student, You're experiencing one of the common problems with the 404 if it sits for a long time. Between the aluminum head, iron block, brass radiator and aluminum pistons, if these trucks sit in damp for very long electrolysis can run rampant inside the cylinders that have open valves. Joe's trucks were in the desert and still got stuck, albeit mildly. If your truck came from an area with a lot of moisture, such as the mountains or coastline, your truck could have a bigger problem.
For example, I've had several come in from europe with seized engines and when I've pulled the head off, the corrosion often resembled white hair (literally) and sometimes completely filled the cylinder. There's no way to compress that, you'll just bend a rod or shatter the piston. I've sometimes cleaned out all the corrosion only to be amazed by the severe pitting of the aluminum which often made the head and pistons useless.
When you add in Mercedes' love of extremely tight piston to cylinder tolerances, I've only been able to free up seized 404 engines (again, from Northern European climates) without disassembly about a third of the time. Considering the cost of a head gasket compared to a whole engine, I don't even bother to try anymore-I just pull the head which is relatively easy and then you can clean out the cylinders, head ports, check the valves and also put heat to the pistons if necessary.
Even then, one time I did all of the above and got the engine running really well, only to have it shatter a piston later on while I was under the hood. The crank counter weights then launched a piece of piston through that cast aluminum oil pan like a bullet. It missed my thick skull by a couple inches and put a dent in the engine compartment. Ruined the block and it would have killed me if it hit me. So above all, be patient and take your time. Your breaker bar may be able to turn it with some luck and a little more soaking, but it may not.
If you do have to pull the head, keep in mind the 404 uses a different head gasket than the automotive versions of the M180.
