I’ve got an exercise stepper machine that looks like this… I’m not positive but I think the manual variable resistant hydraulics works via air compression and not oil. It sounds like air when in use. One of them gave out recently as I was using it. The resistance no longer strengthens or weakens (it turns but the turn does not alter the resistance). I would very much like to fix or replace this if possible. I believe this model is no longer manufactured. I was reading about hydraulics and it sounds like it could be a washer seal type of thing that has been compromised and therefore no longer maintains or alters the seal/resistance. That’s a big assumption. Anyway, I haven’t been able to find a way to open this thing up to investigate and am wondering if I’ve overlooked something or if this thing was welded/crimped/designed so that it must be replaced and could not be tampered with. Any ideas please? There are a couple of areas on the top that are designed to turn (not unscrew, just turn). The big hole at the top is just the area that is hooked up to the frame of the machine. The small little hole area below it is where a protruding piece enters so that it will secure the head in order to turn the system to change the tension.

Do a google search for something like a hydraulic lift spring. Here is a site that sells replacement parts for a Precor. If you can inspect your part for a manufacturer’s name and number, you might contact the manufacturer for a replacement part that matches.
http://www.fitnessrepairparts.com/cart/ViewItem/5000126

I tried calling the number listed on the exercise equipment but received an instant recording redirecting me to a date/sex line. There is no part number on the hydraulic that I can see. Awhile back I searched for the equipment manual online (I was hoping to find either a troubleshooting guide or a parts number diagram/listing) but could not find it (I believe this hasn’t been manufactured for quite some time). If these parts go for around $100 as shown in that link I think I’ll have to just buy something new. I imagine the other hydraulic will fail soon enough and that would put me $200 under which could be invested towards a new machine. I was hoping to find a way to open this up and perhaps replace a simple, inexpensive part within the hydraulic but I really don’t see anything that can be or was designed to be opened up.

I think you are correct about not being able to repair these things. They are built sort of like the hydraulic lift pistons on hatchbacks and hoods. When they fail, you can’t fix them, you just replace them. The problem is to fix where you can buy the replacement cheap enough to make it worthwhile. I believe you would have to replace both at this point to have a balanced pair. I looked around a bit for variable shock absorbers, variable dashpots, etc. but could not find anything specific for an exercise machine. Maybe if you went to check out a new machine, you might discover a similar variable resistance device along with a part number to purchase a replacement at a reasonable price. Sorry I can’t help more with this but these things are designed as throw away items most of the time.

I appreciate your time and help. At least now I know to go ahead and move forward and look towards purchasing something “new” instead of trying to fix/replace it. Lesson learned…don’t buy used exercised equipment…well unless it’s weight plates or something without working parts! :)