Repairing convertible top cylinders
Thought that those of you with a leaking convertible top hydraulic cylinder might be interested in this.
It appears that if your hydraulic cylinder is leaking out of the top seal where the rod goes in and out, you may be able to repair it just for the cost of a 10 cent o-ring, instead of having to pay approx $200 U.S. to get a complete new cylinder from the States, or double that if you replace both at the same time which is recommended.
I just did one of mine, which took me about half an hour after I got the cylinder out of the car. My car is a '68 Torino convertible, but I believe that the Mustangs of the same era would have used similar cylinders.
First, this only applies if your cylinder is leaking out of the top seal around where the rod goes in and out. Original cylinders normally leak here, whilst the internals are probably okay.
Check to see if your cylinder has a circlip holding the top seal in place, if so continue reading. Also, make sure that the actuating rod is not completely rusty or bent, etc, otherwise you will need a complete new unit.
Remove the cylinder completely from the car as per manufacturers instructions.
After you get it out, I recommend expelling all the fluid from the cylinder to start with as otherwise you're going to get it everywhere and/or all over you. Find somewhere to pump the rod in and out til it all comes out.
Try to conduct the following with the rod pushed as far into the cylinder as it will go. That way if you happen to scratch the rod's surface it will only be on the portion which doesn't have to pass through the o-ring seal.
Remove the circlip. Then using some very, very fine strong metal tool ( I used a miniature screwdriver set) try prising out the metal washer which would have been under the circlip. The tool needs to be very fine, as it needs to fit between the rod and the washer. You can also turn the cylinder upside down and tap it on the bench and the washer may work it's way down the shaft and loosen, but don't tap too hard and bend the rod.
Once the top cupped metal washer comes out, it will be followed by two plastic washers with another metal washer in between. Once all this is out, you can then see the rubber o-ring down inside the body of the cylinder. The 2 metal and 2 plastic washers have to stay on the rod shaft, but tape them up at the top end out of the way whilst you work on the o-ring.
Then remove the o-ring with your small metal tool. Don't worry if you break it, although if you do, try to break it only in one part so that you can still make an 'O' shape with it. Find yourself another o-ring exactly the same outer and inner diameter, and with an inner diameter the same as the thickness of the rod shaft. (I found mine in a multi-o-ring kit from a hardware shop. Worked out to about 10 cents per o-ring).
Lube your new o-ring, stretch and pass it right over the top end of the rod, over the 2 metal and 2 plastic washers, and down, seating it fully in the recess where you got the old one from.
Then just slide the 2 metal and 2 plastic washers back down the rod into position, and re-install the circlip. On mine, the ends of the circlip were a real tight fit.
Note: if the little o-rings inside the cylinder where your pipes connect need replacing, also dig these out and replace them.They are easy to see as soon as you disconnect the hoses.
Then re-install the cylinder. Note that you will definitely need to top up your pump with fluid, maybe twice or so, as you lose a fair bit when you expel all that fluid at the start. Mine didn't want to raise the roof at all and you could hear the pump groaning, until I realised I needed to top it up. Then after you have topped it up once, raised, lowered and re-raised the roof, you will probably need to top it up again. The manual recommends raising and lowering the roof 3 times to expel air from the system.
Did mine yesterday. It was leaking enough on one raise/lower of the roof to dribble a small puddle down through the body onto the garage floor. Now - not one drop comes out. Excellent!
There you go. Hope that helps someone. When I started looking on the web, all I found was companies wanting to sell new cylinders for more than I wanted to pay, or old ones on ebay, and you don't know how good they are.
Hopefully you can save some cash for little effort. Unfortunately, if you fix the seal on one side, I understand that the one on the other side is likely to go, but at least you know what to do then.
If anyone has a try, let me know how you go.