REPLACING PTO PUMP

SnowRidge · Feb 12, 2006

As I understand it, the tram pump operates on a closed circuit and pumps oil only when the machine is moving, but the circuit isn't 'oil tight,' and some oil is 'lost' through the pump's case drain. The charge pump is working constantly, as long as the engine is running. The oil lost by the tram circuit internally is replenished by the charge pump. Any oil not used to replenish the tram pump circuit and that lost from the tram pump's case drain goes back to the tank by way of the oil cooler. While the engine is running, oil is being circulated through the filter, the charge pump, and the oil cooler at all times. The charge pump and the tram pump are both inside the same housing, for those reading this that don't own PTs themselves.

Spiffy, I suspect a fine filter anywhere between the tram pump housing and the return port of the tank would be likely to blow seals, probably somewhere inside the tram pump housing. I recently read an article that said plugged filters on case drains can cause serious damage in hydraulic systems. I think a fine filter would look just like a plugged filter in this case.

Bob999 · Feb 12, 2006

<font color="red"> However consider this, all fluid flows back to the tank eventually, and then is recirculated through out the system. All pumps use the same fluid and get hot and are therefore cooled by the hydraulic cooler. </font>

I share your understanding that the tank is common to all systems--It is the source and return point for each of the three separate systems on most PT units--tram or variable displacement pump circuit, PTO circuit, and steering/lift circuit.

However, my understanding is that the flow through the hydraulic cooler originates from the charge/variable displacement pump. Thus fluid pumped by the PTO pump goes back to the tank without passing through the cooling coil. Similarly fluid pumped by the steering/lift pump goes back to the tank without passing through the cooling coil.

BobRip · Feb 12, 2006

Having a fine filter in parallel with the coarse filter would give some flow through the fine filter. Fluids do not just flow through the path of least resistance, they flow through the other paths as well, just more flows through the low resistance path. It is just like two resistors in parallel. The lower resistor value carries more current (fluid), but the higher resistance resistor carries some. I don't know what the ratio would be.

Bob Rip

Bob999 · Feb 12, 2006

<font color="red"> Perhap this is what you guys are getting at, but what about a fine filter right before the cooler? I'd still want to monitor the pressure -before and after to determine feasability, and during to determine filter life. I picked up a 5000psi glycerin filled gauge for under $20 the other day.
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I think that the pressure in the cooler is quite low--first because the charge pump pressure output is relatively low pressure and second because there is an unrestricted line from the cooler to the tank. However if you were to put a 1 micron filter in the circuit pressure could build up as the filter loaded up.

There are special cleanup filter units made to refine the fluid in hydraulic systems. My understanding is that they typically use a 3 micron filter element and have a separate motor/pump and use hoses to take fluid from and return it to the reservoir. These systems are used when the tractor is not operating. Ones I have seen cost several hundred dollars.

J_J · Feb 12, 2006

I have already plumbed quick disconnects to several circuits on my 1445. I just plug in the gauge when I need to read the pressure. I don't think the pressure will be any higher than 3000 psi. I think that the relief valves are set at 2750.

J_J · Feb 19, 2006

I received my PTO pump the other day, and installed it Only took about 20 min to take the old pump off, two bolts and two hyd connectors. Two bolts to install the pump, and new o-rings on the connecting plugs and hooked everything back up. I still have to lower the engine assembly back down and bolt it down. I haven't made up my mind about using 10W40 motor oil or synthetic motor, or synthetic hyd oil.