Yanmar Hydraulic Problem.

I have a Yanmar tractor, model YM165D, that each time I start it, I have to prime the engine driven hydraulic pump. Can anyone give me some information as to what the problem may be?

Thanks and have a great holiday season.

Does it use the transmission as a hydraulic sump like my Yanmar/John Deere?

If so, is the fluid up to the proper level?

I don't know your YM165, I have a Yanmar 240d
when I left it out in the rain, water got in through the rubber boot on top of the trans, through the shifter and would freeze, the hydraulic fluid will be milky.

Also water will get into the stering and cost large. Through the tube under the stering wheel.

Here are some good YM sites.

http://www.external_link/wwwboard/Yanmar_tractors.html

http://www.external_link/forumdisplay.php?f=69

http://www.tractorbynet.com/forums/yanmar/

I forgot, if you are new to yanmar tractors . . . there is a screen in the bottom of the trans V shaped w/3 or 4 bolts, if it's plugged with Trans grindings the pump can't suck properly.

Tom, Thanks for all the information. Oil is not milky, but over filled looking at the stick. You mentioned a filter in the gear case. Some time back, possibly 3 years, the oil was drained from the gear case and the filter removed and cleaned. Can"t tell you whether the filter was put back in properly. Should I drain the oil again and check the filter? Can it be put in backwards? I forget how much oil I had to buy for the guy, but it seemed to be about 4 gallons. I can tell you that when I start the machine now, I remove 3 screws that hold a small bracket on top of the pump, this shows me the pump gears, I start the engine in a very slow idle, pour oil into pump, engine RPM's change and suddenly the noisy sound of empty gears disappears and the hydraulics start to work. After they are working, I can go all day and have no problems. It seems to me, from working on water pumps, the pump is losing it's prime and the oil I put in primes it. Do you know of a check valve that may be leaking allowing all pressure and oil to go back to reservoir?
Again, thanks for your information and the web sites to follow up on.

Fawteen, I believe the same oil is for the hydraulics and rear axle. I checked the oil level and it is above the dip stick so no shortage of oil. Do you know of a check valve in the system that will allow oil to drain from the pump, thereby requiring priming each time it is started? I can start the machine and set throttle at low idle, pour oil into pump, (prime it in effect), (gears are noisy trying to suck oil), then suddenly the RPM's change and the pump loses the noisy sound, the hydraulics start to work and will work for as long as I use the machine, sometimes upwards of 10 hours. Leave it until next day, have to start the scenario over again.

Thanks for your input.