Roof Hydraulic Cylinder and Hinge Leak, DIY Rebuild

S

Sh_1

New member
Hello everyone,

I’ve been searching and reading for days, but I haven’t found any discussion on this topic. If a thread exists, I apologize.

I noticed that the roof lowers and raises more slowly and that the sound of the whole system is slightly different.
I removed the roof and inspected the motor and hydraulic pump, tested the roof while detached, and the pump moves the oil - the roof works. However, a leak is noticeable from the left hinge.
I am aware that this is a bidirectional hydraulic piston and that it is necessary to replace the seal. That’s all.
But…
I managed to remove the lower part of the cylinder as shown in the pictures, but further disassembly stopped me with this rebuild.

I know these parts are successfully sent for rebuild to Tophydraulics, but I am interested in fixing it myself.

Has anyone disassembled a complete cylinder, and does anyone know the next steps to successfully complete the rebuild?

Thanks
 

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If you can apply some hydraulic or air pressure to one of the ports (don't know which one) it should push the piston out of the cylinder. If you get it apart pleas post pictures for future reference for everyone. Good luck!
 
Are you 100% certain the leak wasn’t just from a pinhole in the lower hydraulic pipe? That is a far more common occurrence.
 
First time I've seen one of these taken apart, can you take and post pictures of the bottom part you removed. Specifically, the top part where there should be a rubber gasket of some sort and the side hole where the hose plugs into. The large o' ring on this part looks from the picture to be solid. However, I'm only looking at a pic.

Have you uncovered any evidence from looking at these parts of rubber 0 ring failure? How about the seal where the bottom hose plugs in, any visible failure? Some people claim that there are small o rings which attach to tip of the metal fittings on the hoses. Did you find any evidence of these small o rings?

Hope this works out for you.
 
You have to remove the clip and press out the lever that attaches to the rod with gear.

I can simply knock it out but to assble it back you have to use G clip with socket like how you install a bushing.

I bought exchange rebuild cylinder from china for about 300USD and they did not come with the lever so have to transplant them and send the core back to get deposit refund.

If you still can't remove the rod, drill the upper part like what you did to the lower one, that seems like what the china rebuild company did to the cylinder

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There was a Taiwan company did the repair by cutting it open
does not seems necessary, however this is the only pic I can find online about how it looks inside
Screenshot_20250408-181051.png
 
For now I think the rebuild procedure should be: drill the upper and lower notch, take the upper seal out with shaft and lower seal out as well.

Turn the piston anti clockwise to remove it from shaft, take the shaft out, replace the rod seal inside upper seal block, replace the outer oring on piston, upper and lower block , assemble back and use bolt to secure upper and lower block to replace the function of notch that has been drilled off.

Anyone wanna try?
 
OK I will try - but has anyone done this since the last post? I see that you can get the rod seal quite cheaply. If so can you give me a little more information on the results.

Thanks
 
nexcorp said:
OK I will try - but has anyone done this since the last post? I see that you can get the rod seal quite cheaply. If so can you give me a little more information on the results.

Thanks
Click to expand...
Ok I'm sure how it's done from the Chinese repair site.

Just look at the picture an you know how it should be repaired.

To replace the dent that holds the end with gasket, they screw the small hex bolt in.

1000012172.jpg
And here's the new refurbished exchange pair of cylinder I got from China
1000008486.jpg
 
Thank you.
I have got the cylinder apart now without damaging it but so far I have not been unable to unscrew the piston from the rod/shaft.
I do not want to damage the piston or its seal. So far I have tried clamping the piston in a vice between two pieces of plastic but it does not want to unscrew. I do not want to squeeze it too much and distort the piston or destroy the piston seal.
Have you actually unscrewed the piston successfully?
 
Rod seems to have an even thickness flange on the end. It does not look like it is threaded?
 

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Rod itself is 12mm and flange at end of piston is 11.5mm.
Looking at the rod it is possible that it is threaded on to the gear rack at other end but not sure.
I have tried clamping piston as tight as I dare and then unscrewing. Either gear rack or piston should come off this way if threaded but neither moves - piston just slips in my clamp. I assume that if threaded then there will be locktite on the threads so will be tight but I am not sure how I can apply more clamping force without damaging the piston or rod.
 

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I asked the China guy who rebuilds the cylinder and sells repair kit, he says yes, twist it off, it's threaded. I think clamp the gear rack and clamp and twist the piston is the right way. Also he says the bottom end metal plug has to be replaced. He offers 2 bottom plug and all the seals needed for around 160 usd.

I think if you can secure the bottom and able to seal it, should be fine.
 

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Last edited:
nexcorp said:
Rod itself is 12mm and flange at end of piston is 11.5mm.
Looking at the rod it is possible that it is threaded on to the gear rack at other end but not sure.
I have tried clamping piston as tight as I dare and then unscrewing. Either gear rack or piston should come off this way if threaded but neither moves - piston just slips in my clamp. I assume that if threaded then there will be locktite on the threads so will be tight but I am not sure how I can apply more clamping force without damaging the piston or rod.
Click to expand...
Use a little heat from a torch. That will break loose the loctite.
 
Folks. I've been lurking. Wonder if this has gone farther. I just purchased a Z4 with the same top problem that everyone has. I'm on a budget and also trying to figure out the DIY process. Not trying to hijack thread, but: I too found a source for the rod seal. But not the piston seal(s) or o-ring. Anyone find a kit with all 3 or source the proper O-Ring and Piston seals? Or have exact dimensions of the O-Ring and Piston seal(s)? Or has the Chinese link hit ebay? I couldn't get past the signon either. And I don't see anything in aliexpress.
 
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