300 U hydrualic falure

300 dave

Member
My 300 U is now showing complete failure of hydraulic system; i.e. no movement of cylinder what so ever. Fluid level is FULL, operating handle is engaging the shaft on the spoiler box. Nothing is happening. I had trouble last winter. After posting here, I drained fluid, heated over night, and all worked fine. Is it possible that the screen in tank is sucked so flat that no fluid at all can get through? What else could be wrong? I have noticed that every once in awhile there is a kind of funny sound coming from the hydraulic pump. It is very brief and may slow the engine just enough to notice. Could my pump be shot? If pump shot, can it be rebuilt for less than a new one? Where to do this? thanks all
 
Examine the piping or hoses between the pump and the hydraulic unit for leaks. The steel lines in particular like to crack quite often where they connect to the block that bolts on the pump. When they crack if it is on the suction line the pump will suck air and not prime. If it is does end up being a worn out pump they were designed as throw away units not to be rebuilt.
 
The screen inlet is a sore spot, but usually doesn't cause instant failure, A stuck regulator or stuck open safety regulator valve can do that. Parts 6 through 10 are possible problems in light of the periodic buzzing noise it made. Parts 12 through 15 are pressure regulator. Jim
Diagram
 
thanks guys I meant to add that with filler cap removed I see no movement of fluid in the tank what so ever.
 
yes I been down this road several times. The steel tubes seem to me to be a bad idea. The vibration is too much for the press in mounting system. I repaired several and keep spare sets on hand. some day I will change that over to a flex tube mount all the way. someday...
 
Went through the exact problem with mine about 4 years ago. Sure enough the filter was completely collapsed. It's a bit of a wrestling match getting the cover of the hydraulic tank. I replaced the filter and it worked fine.
Fast forward, my pump, which started with a small drip began to leak heavily. It was also leaking from the front side into the engine oil. I purchased a pump kit and with help here rebuilt the pump. So far so good, no leaks.
 

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