Granite State

Guess what I'm doing!

Granite State

Has anyone found two different rod seals on their front top locks?


Quite a difference between the two. I suspect the one on the left has been replaced before.

bobterry99

Someone has worked on the cylinder on the left. Originally this unit had a "rod seal" which evidently failed. Rather than replacing the rod seal with another rod seal they chose to use an o-ring.

For $150 you can buy a set of rod seals from eBay which will repair all of your cylinders.

Granite State

Understood, but my point was that there are two distinct different seal grooves. I haven't seen that before. My replacement seals will not fit in the smaller of the two grooves. I haven't encountered this in my previous research and was wondering if anyone else has and what they might of done. I wasn't aware of the difference in the rods. The housing part numbers are the same but obviously the internals are slightly different, enough so that it creates a problem.

I might be forced to purchase a complete rebuilt cylinder if I can't find a solution.

bobterry99

You asked about rod seals, but apparently you meant to ask about piston seals. There is rarely a need to replace the piston seals, and I have never seen a rebuild kit that includes them.

Granite State

Sorry, I apparently got it backwards. I assumed the "rod seal" was actually attached to the rod and the aluminum piece was the piston. I just heard from mbseals and he said that the seals around the brass end of the piston don't usually get replaced as they are only for guiding inside the housing bore. I jumped the gun and removed them before I got the seal kit. I appreciate your response and I'm getting a hands on lesson in MB seals for sure.

In the construction industry, the long shiny shaft is generally considered to be the rod and the aluminum piece is the piston. I guess the MB world looks at them differently.

bobterry99

I have edited one of your photos to identify the piston (red circle) and the rod (yellow rectangle).

The rod is attached to the piston, and both move, of course. The rod seal is stationary and housed inside the end cap.

Tophydraulicsinc.com may be able to bail you out of your predicament.

Granite State

Much obliged. I'm in good shape at this point. The seals I removed from the piston aren't perished yet so I'm going to reuse them. They are only used as a guide for the piston/rod assembly and don't really "seal" anything. Live and learn, I say. I appreciate you helping out.

bobterry99

I believe that seal is analogous to the compression rings belonging to an engine piston. If the piston seal is compromised, then hydraulic pressure will be lost within the cylinder, and the roof may not function properly.