Hydraulic Lift Cover Leak

Can you tell me what is causing a leak around my hydraulic lift cover on my TO-30? This happens whether I use a light or heavy implement.

The cover must fit well and have a clean gasket seal with the center housing to be leak free, particularly where the tube from the pump exits to deliver oil under pressure to a hole/passage in the top cover that transfers the oil to the lift cylinder. The tube runs along the right side of the housing forward of the right inspection plate. That tube runs through holes in the top and bottom of the center housing casting to transfer oil under pressure from the hydraulic pump to the internal lift cylinder. The ends of the tube are flared at either end when the tube is installed. Once installed, the tube rarely requires service unless it is damaged. If the side seam of the tube splits, it can spray oil on the seam between the top cover and the center housing, possibly causing a leak.
Other possibilities include a crack in the lift cover, or a problem with the gasket between the bottom of the top cover and the lift cylinder. The lift cylinder is held in place by four bolts with nuts on the top of the lift cover. If they are loose there is the possibility of a leak. There is either a gasket or O-ring to seal the joint between the bottom of the top cover and the top of the lift cylinder casting at the front. TO-30’s originally used an O-ring but replacement parts sometimes use a gasket like the earlier models.

There should also be two small gaskets between the rear of the lift cylinder casting and the top cover at the mounting bolts. These gaskets act as shims, if they are left out it will compromise the seal at the front. There are also two socket-head pipe plugs on either side of the top of the lift cover housing near the front for connecting auxiliary hydraulic cylinders or valves. Make sure the plugs are still sealing properly. On rare occasions the bottom of the hex opening can develop leak.

Look for oily residue; that is your best indication of the source of the leaking oil. Clean the area thoroughly and then inspect the area following each use. There are leak indicator products you can add to the oil to aid in locating illusive leaks. These are dyes to change the color of the oil to aid in leak detection. These indicators are available at most automotive supply stores.