Replacing Convertible Top Hydraulic Cylinders
Convertible cars come with convertible car problems. One is the occasional failure of the hydraulic systems in those cars. In an earlier article, we have already discussed replacing your convertible top motor. Here we are going to cover replacing the convertibles’ hydraulic cylinders. The procedure is a bit more complicated, but you don’t have to take it to an auto shop or even be an ace auto mechanic to perform this type of hydraulic cylinder repair. And it doesn’t much matter if your droptop is a vintage Cadillac, a newer Ford Mustang, Chrysler Sebring convertible, or even a custom convertible, the procedure is roughly the same for most American ragtops.
Begin by putting the top in the down position and removing the rear seat. Next you will need to expose the hydraulic cylinders. This is accomplished by removing the interior quarter trim panel which is the panel the rear window crank is protruding through. These panels are held in with a series of screws, bolts, or clips depending on the make and model of the car. Use care when removing these panels as some clips may be hidden and damaged if you force their removal.
Once the cylinder is exposed, you will be able to unbolt the cylinder from the convertible top frame and body of the car (there should be access holes provided to make this job easier). With the cylinder disconnected from the body of your ragtop, all that remains is disconnecting the hydraulic lines.
Be forewarned!! The cylinders will drain their fluid once the lines are disconnected. So, unless you quickly screw in a same size bolt into the existing line hole to stop the flow, have a catch basin and shop towels ready for such an event.
CAUTION: Pre 1953 convertibles use DOT-3 brake fluid in their convertible hydraulic systems. !962-67 used either DOT-3 or automatic transmission fluid. After 1967, convertibles had transmission fluid in them. The reason for the caution is, DOT-3 brake fluid quickly destroys paint (go on, ask me how I know). Use extreme caution when working with brake fluid. Also be aware that some convertibles have been converted over to tranny fluid. You could cause hydraulic damage if you use a mixture of the two in your system. (Click here for DOT-3 Brake fluid or transmission fluid)
After the cylinder is removed, you are ready to replace it with the new cylinder. Your new cylinder will arrive in the retracted or ‘down’ position, making it impossible to install as is. Therefore, you will have to partially extend the cylinder rod. To do so, add a little thread sealant to the hydraulic line and connect the line. Tighten as tight as you can by hand then, using a line wrench, tighten another quarter to half turn. Don’t over tighten!
Now place the new cylinder in its proper location and bolt to the body of the car leaving the cylinder rod end unattached. At this point the rod and convertible frame will be separated by some space. To close the gap, you will probably have to manually lift the top. It is best to have a helper for this step. Your assistant will hold the top in the upright position as you align and connect the cylinder rod. Your assistant will probably find it easier to hold the top by standing in the car where the back seat resides.
Sometimes you will find it necessary to partially extend the rod out of the cylinder to make the two meet. To accomplish this, remove the fill cap on the reservoir. Place a towel under the reservoir. Then add the proper type fluid until it just begins to cover the fill hole threads (begins to drip out). Hit the switch to extend the rod to the needed length. Remember not to hit the switch for longer than 15-20 seconds at a time so as to avoid heating up and damaging the pump.
Once the final cylinder connection is made, check the reservoir level. Now run the top cylinders through 1 up and down cycle. Again top off the reservoir (Check the reservoir after each up and down cycle). Repeat this process until both cylinders are performing correctly. By leaving the reservoir cap off as you run the cylinders up and down a few times, you should simultaneously be bleeding the convertible top hydraulic system. However, if for some reason there is still air in the lines, you will have to purge the system of all air pockets.
Once everything is connected and all air pockets have been eliminated, give the whole hydraulic system a visual inspection for leaks. Double check each hydraulic fitting and make sure the reservoir is tightly capped. Run the top through the paces a couple more times, and if everything is A-ok, reassemble the car.
Now that you spent the afternoon working on your ragtop, go spend your evening driving it.