hydraulic help please at witts end!

LOOMER · Jan 31, 2009

Well i finally got frustrated enough to drop her off at the doctors. It will probably be expensive but i will end up saving the barn. The more i worked on the more frustrated i got and things where getting thrown. Ill end up spending more money on barn repairs do to flying tools.

I will keep you all posted thanks for your input.

rbento · Feb 1, 2009

This problem reminds me of a fuel problem i had. my kubota kept quiting anytime after running fine for a while. Long story short I found the bar code label from the fuel cap floating around in the fuel. sometimes it would stop up the fuel line inside the tank then float away again. Finally i looked inside the tank with a flashlight and caught a glimps of it stuck to the side of the tank.

Another time I had an air leak in my oil furnace. replaced everything pump and all, except one fitting. finally bought a fuel/air filter called a Tiger. That filter burps the fuel before it goes to the pump.
i know these comments are not hydraulic issues but what the heck, you never know what you might learn from someone and besides it already went to the Doctor.

J_J · Feb 1, 2009

LOOMER said:
Well i finally got frustrated enough to drop her off at the doctors. It will probably be expensive but i will end up saving the barn. The more i worked on the more frustrated i got and things where getting thrown. Ill end up spending more money on barn repairs do to flying tools.

I will keep you all posted thanks for your input.

You said it empties out the reservoir and cooler, but where did the fluid go, Is it on the ground, or what. A reservoir is usually 2 times the capacity of the pump. If the pump can pump 8 gpms, then the reservoir would be about 16 gal. If you emptied out the reservoir, you would definitely see it somewhere. If you have air bubbles as you have stated, then you are sucking air. If you were to ever empty out the reservoir, then you would really suck air, and when you replenished the fluid, there would be air in the system.If that pump cavitates enough, it will destroy it self.

I would definitly check the input line, and filter. Maybe something got in your hydrauic tank and stopped up the line going out of the tank.

It is just amazing to me that those bubbles bursting could cause that much damage. Even ship propellers will cavitate sometimes, and the result will be that the trailing edge will were down and change the efficiency of the propeller.

john_bud · Feb 1, 2009

It's obvious from here (yeah right!) that your return line to the reservoir is clogged up and no fluid is getting back there.

Now we have to wait to see what the "pro's" have to say.

JJ - My TLB has a 18 gpm pump and a 5 gal reservoir and it's all factory. So you may want to modify your statement slightly.

jb

J_J · Feb 2, 2009

john_bud said:
It's obvious from here (yeah right!) that your return line to the reservoir is clogged up and no fluid is getting back there.

Now we have to wait to see what the "pro's" have to say.

JJ - My TLB has a 18 gpm pump and a 5 gal reservoir and it's all factory. So you may want to modify your statement slightly.

jb

jb,

I think one should use whatever it takes to keep the hydraulic fluid below 200 degrees, preferably around 180 on the hottest days and working the tractor or unit hard.

Tank functions
The main reason the reservoir exists is to store fluid. The accepted rule for sizing a tank is: the tank volume should be two to four times the pump flow in gpm. This is only a general rule. Some circuits may require more volume, while less fluid may be adequate for other circuits. A 25-gpm pump would work well with a 50- to 75-gallon reservoir for most circuits. With this general rule, the returned fluid theoretically will have two to three minutes in the tank before it circulates again. As Figure 6-5 shows, a baffle separates the return line from the pump inlet line, forcing the fluid to take the longest possible path through the reservoir before returning to the pump inlet. This arrangement also mixes the fluid well and provides more time to drop contaminates and de-aerate. In addition, the fluid spends more time in contact with the outer walls of the reservoir to dissipate heat.

The other option is to have a super large cooler.

Those are not my figures, but all the data I have read, suggest 2 to 3 times in gal, the capacity of the pump. Here is an example of some data.

Hydraulic Reservoir / Tank Size Calculation- Jythra Engineering Services - CAD CAM Services

kenstrac · Feb 2, 2009

I believe this is a closed hyd system it has 2 pumps a charge pump and a variable displacement pump the reservoir he is speaking of is an accumulator that only hold approx 2 gal it also has a priority valve that from previous experiences is the problem .

J_J · Feb 2, 2009

kenstrac said:
I believe this is a closed hyd system it has 2 pumps a charge pump and a variable displacement pump the reservoir he is speaking of is an accumulator that only hold approx 2 gal it also has a priority valve that from previous experiences is the problem .

You still have to have a large enough reservoir for all hydraulics functions, not only hydrostatic transmission, but power steering, loader cylinders, etc.

kenstrac · Feb 2, 2009

What I said was the 2 gal was the accumulator not the reservoir the reservoir is in the transmission housing.the accumulator is there to give the VDP a charge when it kicks into pump mode.

BTW the charge pump is located in transmission it has a large suction tube leading from the filter housing that pump is a very rugged pump and has a very thin tube on pick up side the only seal it has is an O-ring the only way to properly check this system is with flow and pressure gauges inserted throughout the system if you do not have charge pressure and volume it will not fill accumulator starving front pump

LOOMER · Feb 2, 2009

Sorry you are correct there is a trany resivor which is the main tank. There is also a resivor that sits on top of the pump wich seems to be supplied by the cooler. Should get doctor results today.