Backhoe LW-7 backhoe foaming out the dipstick

[johneic]

John,
Did we ever check the direction of flow on the filter head? In & out?

.

Yes, flow is right

 

[J_J]

Perhaps if I explain how the closed loop hyd system works on out Power-Tracs, you might understand why we use a suction filter.

Hydrostatic transmission don't like any particles of anything in the fluid, so the engineers at Power-Trac, and I supposed Eaton, who made my pump, determined that a suction filter at the input to the charge pump would provide fresh filtered fluid to the VSP pump. [ Variable Speed Pump ]

This VSP pump being in a closed loop circuit, pumps the fluid to all the wheel motors, and back to the input of the VSP pump. The charge pump volume is about 20 % of pump volume. Charge pump pressure is about 300 to 450 psi, and is used to keep the VSP pump charged and full and flush the heat out to the cooler.

The fluid from the charge pump not used is sent through to pumps case, and to a cooler and then to tank. My wheel motors also have a case drain, and all fluid from the wheel motor drains go to the VSP pump case and then to a cooler and then tank.

I change out the 10 micron filter about once a year .

 

[RonMar]

Hydrostatic systems have a Charge pump, designed to deal with pulling fluid thru a suction filter before feeding the variable displacement pressure side of the hydro unit... Kind of like the lift pump that feeds a diesel injector pump... Like an injector pump, the variable displacement pumps are fairly precise and do not feed on particles well...

 

[Rich Waugh]

Yep, and our tractors don't have charge pumps, and if they get restricted on the intake (for whatever reason) the pump will cavitate and foam the fluid and ultimately trash itself. That's why I think a 10 micron intake filter would be very risky on our tractors.

 

[Bob Rooks]

As on my Mustang, the charge filters are very large and have a high capacity and flow rate. It should be noted that suction side filters with large capacities (I don't mean flow rate, but the capacity to hold contaminants before service is due) aren't going to hinder pump performance.

 

[johneic]

Just so this is clear I am using a:
25 GPM SUCTION LINE FILTER
New ZINGA. Spin-on type element. Ports 1 1/4" NPT.
SPECIFICATIONS
Suction Line Applications 25 Micron
25 GPM
5 PSI bypass
950 sq in filter area
5 1/3" dia x 9 1/3" long

25gpm for a 7 gpm pump sounds fine to me

I finally got time to work on this today, I am putting two constant torque hose clamps on all hoses, the second one pinches on top on the ridge at the end of the nipples. Every place a leak may occur is getting a coat of rtv, its sloppy, I'll clean it up with a razor blade later. I have finally had five days of sun and its dry enough to drive the tractor on the dirt tomorrow so I am doing this on new years eve, Happy New Year!

I reused the O-ring on the tank outlet fitting(originally), I didnt like how it looked, I have removed it and cleaned it good with carb cleaner and am sealing it with rtv.

I am going to remove the filter and re-oil it and retighten it.

I think I am catching every place I might get air intrusion.

I used Loctite 545 on all the pipe fittings, I am not breaking them loose at this point.

If I still have a problem tomorrow I will get a fitting and remove and bypass the filter

Note- the flow is right on the filter

If I am missing something, let me know, any ideas are welcome.

 

[RonMar]

Sounds lika a good plan...

 

[johneic]

Ok, first problem, without the o-ring the outlet fitting tightened up to an unusable position, so I removed the fitting, reinstalled the o-ring-I figured it should seal this time with all the rtv and tightened it up its a tad higher than the first time I assembled this (I hope thats OK).

Second problem, I could not remove the filter by hand and its too big for any filter wrench I have ,I didnt want to ruin it by putting a screwdriver in it (I do have a spare though). So I am leaving that for now, will seal it with rtv around the edges in the morning.

In the first picture I am cleaning the tank outlet with carb cleaner sprayed onto a brush (I didn't want to get the carb cleaner in the tank)

 

[Bob Rooks]

That all looks good John, but I question two things.
1) The eyebolt on the pumps reaction bar: Was that a grade 2 eyebolt or was it a hook. If it was an eyebolt it's ready to let go. (I use a forged eyebolt on mine.)
2) The hose clamps. The constant torque type that you used have little advantage over the previous worm drive clamps. The T-bolt type clamps have a tremendous advantage. But we'll see what happens tomorrow.

Happy New Year :thumbsup:

 

[johneic]

1) The eyebolt on the pumps reaction bar: Was that a grade 2 eyebolt or was it a hook. If it was an eyebolt it's ready to let go. (I use a forged eyebolt on mine.) :

Two "D" rings actually, one started bending so I added an extra, I like the idea of an eyebolt, I never would have thought of it

Eyebolt came with the pump.