The Hyd fluid used is Mil-PRF-83282, I think. I left the Marine Corps 4 months ago. Some things I have forgotten. I don't remember the engine or gear box oil Mil-specs, but I'm sure they still leak. The Hyd leak on my 1/72 scale CH-53E is meant to represent a rotor positioner leak. The night I added the finishing touches on my CH-53E there was a rotor positioner leak on an A/C we were trying to push out of phase. It kept us at work for an extra couple of hours, so I had to include it on the model.
I just keep chugging away at the 1/48 scale kit. I hope that I'll be able to close up the fuselage soon, but It all depends on the upper sound-proofing and little things like the upper crew door/AO window, and other cabin details. (I need to add the guns, and I think they'll need to detailed a bit.)
I considered cutting the 1st Stage Hydraulic compartment/Main Gear Box Oil Cooler Compartment open. However, I decided that there was enough work to do on this model without cutting open compartments. (The 1st Stg Hyd compartment is located aft of the Main rotor head on the upper right side of the aircraft, opposite the #2 engine).
Good luck to you on your 53D. The Forward Hyd compartment on a 53D has 3 hyd systems as opposed to the 53E's 2. I Couldn't cut open a Forward Hyd compartment. There are just too many lines and components to scratchbuild. It'd keep my busy to 2010, and I can't go 4 years without adding anything new to my shelf.
I'm going to have to make some of my own decals for this project, which I'm sure will be fun. The thing I hate about making decals is the time spent sorting stuff on the computer. I'm not looking forward to that process, but I'll burn that bridge when I come to it.
I'll keep updating my battle with the Academey 53E. The Academy 53E isn't as frustrating as the Sikorsky 53E, but it still has me cursing form time to time.
I added some seats to the cabin. It's a better representation of the cabin, but it's not exactly perfect.
Semper Fi,
Chris