How to bleed your system

Convertible Top Pump, Cylinder, and Hose Installation Instructions

How It Works

Most modern cars use an electric motor to turn a hydraulic pump which supplies pressure to the lift cylinders located on each side of the car. The pump is usually located in the trunk area of the car and will most likely be held in place by 3 or 4 pointed grommets which push into holes in a bracket, the rubber grommets provide a cushion to reduce noise when raising and lowering the top. The pump assembly is a 1 piece unit that consists of an electric motor on one end, a small hydraulic pump in the middle and a fluid reservoir on the other end, the reservoir is held in place by a bolt that goes through the center of the reservoir into the pump, do not remove this bolt! 

To check the fluid level there will be a 'push in' rubber plug or a slotted screw in plug located on the end of the reservoir above the center line, the fluid level should be to the bottom of the hole when the top is in the down position. When you operate your top switch to make the top move, this turns on the electric motor and the pump will take fluid from the reservoir and pressurize it, it will push the fluid through the lines to the cylinders.

The fluid goes to the cylinders (it enters the bottom of both cylinders to make the top go up or to the top of the cylinders to make the top go down) as the fluid enters one end of the cylinder the top will begin to move and fluid is pushed out of the opposite end of the cylinder and returns to the reservoir through the hose. The pump is capable of producing between 300-450 PSI depending on the type of pump and year of car so use caution.


Most cars 1967 and newer use automatic transmission fluid, from 1962-67 they may have used either automatic transmission fluid or brake fluid.  Brake fluid can be detected by its pungent odor and transmission fluid smells more like oil.  Pre 1962 cars almost always came with brake fluid but should be checked because the type of fluid in the system may have been changed, mixing the types of fluid may result in parts failure.  If you are replacing the complete system, the use of automatic transmission fluid is recommended, never use silicone brake fluid as this will void any guarantee.


Pumps and cylinders purchased from Convertible Top Specialists may be filled with fluid, this fluid will either be Dextron III automatic transmission fluid or mineral hydraulic oil.  The fluids are compatible with each other but not with brake fluid. The complete system holds approximately 1 1/2 to 2 quarts of fluid, use extreme caution if your system contains brake fluid as it can damage the paint on your car.


Never totally fill your pump reservoir with fluid, fill until fluid runs out the filler hole or until the reservoir is approximately 3/4 full.  A meat baster works good to fill your pump, just don't tell your wife you used her turkey baster as it can he hazardous to your health. 

If you are installing a new pump only, filling the pump reservoir 3/4 full and connecting the hoses and electrical connector should be all that is necessary.  However after running the top up and down 2 times it is recommended that you check the fluid level with the top in the 'down' position, you can leave the plug out of the reservoir when testing the top operation as there is no pressure in the reservoir and this will help allow any air bubbles to escape. 

You should never run the top motor for more than 15-20 seconds at a time to prevent damage. Remember that  the cylinders can exert over 1000 pounds of force and can cause considerable damage if you are not careful.

Our Cylinders

Some 1963 and newer cars top mounted cylinders are designed to be installed without the use of nylon bushings, it is one less item to worry about and it results in a much smoother operation.  If your cylinders come with plastic bushing installed you should use them, if they do not come with plastic bushings then none should be used, do not try to use your old bushings as they will not fit.

Replacing Cylinders

Remove the old cylinder and install the new cylinder in its place.  The new cylinder will have its piston in the 'retracted' or 'down' position therefore attaching it to the top frame will not be possible at this time.  Operating the top pump will fill the cylinder with fluid and extend the piston rod until it can be attached to the top frame.  While filling the cylinder the pump should only be operating about 15 seconds at a time to prevent overheating, check the fluid level at this time and refill if necessary.  Leave the filler plug out and place a rag under the pump to catch any spillage until the unit is bled out and filled.

The piston rod must be watched closely during this process to prevent damage.  When the piston rod is extended to the proper position attach it to the top frame, you will now be raising the top frame as you are bleeding the system.  The fluid level should be checked and refilled (if necessary) each time the top is returned to the down position. 

Running the top up and down 3-4 times will bleed the system and the filler plug may now be installed, assuming there are no additional problems your top will be in good working order.