I overhauled my hydro pumps after a slow leak for a couple seasons now. After replacing the seals and reinstallation, I followed the procedure to purge the system while the transaxle is released, then reengaged, but still have frothy oil. I can’t find any leaks from the pumps anywhere and the connections are all tight for the hoses. I replaced all of the low pressure hoses and the two drive hoses for the right hand side. I have followed the purge procedures 4-5 times and still seem to have air. Is this normal? Any suggestions from the group? I’ve never worked on hydro systems before, so any advice is appreciated
Scag Tiger Cub Hydro Pump Air Pocket?
- Thread starter ngrobb01
- Start date
I have had a couple that I have ran at idle for a few minutes doing the purge with the frothy oil, and I will shut it off and let the air settle from the oil and then purge again. Sometimes it takes a few times. Especially with separate pumps and wheel motors with new hosed. That is a lot of air that has to purge from multiple places.
Hose to wheel motors and wheel motors are the worse because the oil outside of the pump and in the return tank is just make up oil. Think of the drive system as a closed loop and only calls for outside oil when part of it leaks due to internal pump lose.
Hose to wheel motors and wheel motors are the worse because the oil outside of the pump and in the return tank is just make up oil. Think of the drive system as a closed loop and only calls for outside oil when part of it leaks due to internal pump lose.
After looking further into the purge process I only cracked the bypass valves maybe 1 full turn out instead of 3-4 full turns. I’ll give that a shot and see if it makes any difference given the amount of air introduced as you mentioned.
Still having trouble purging air. Backed bypass valves out 4 turns on each side and purged multiple times with letting it sit and idle for a few minutes then turning off and letting it settle between rounds of purging. Left pump still running anywhere from 150-170 degrees, right pump consistently between 115-125 degrees. When using a mechanics stethoscope the sounds from the right pump are more pronounced when placed on top of the charging port vs the left. I don’t know a lot about hydro systems, but I would assume the sound is more prominent because of the fluid in the pump? Could it be there is an air pocket in the charging port? Any help would be appreciated as I’m ready for this to all be in the rear view and bring it to a shop from here on out.
Still having trouble purging air. Backed bypass valves out 4 turns on each side and purged multiple times with letting it sit and idle for a few minutes then turning off and letting it settle between rounds of purging. Left pump still running anywhere from 150-170 degrees, right pump consistently between 115-125 degrees. When using a mechanics stethoscope the sounds from the right pump are more pronounced when placed on top of the charging port vs the left. I don’t know a lot about hydro systems, but I would assume the sound is more prominent because of the fluid in the pump? Could it be there is an air pocket in the charging port? Any help would be appreciated as I’m ready for this to all be in the rear view and bring it to a shop from here on out
Just had a thought when I went back and reread your OP. You said that you overhauled your pumps. Did you remove the football shaped cover with the oil pump in it. If so it could be possible that they have been reinstalled 180 degrees from original which will prevent proper purging because they would be trying to pump the oil out of the system instead of pumping into the system.
bertsmobile1
Lawn Royalty
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I have had some mowers that just will not purge no matter what to the point I had to rig a vacuum pump up to suck the air out.
The other big thing is the wheels must be off the ground so they offer no resistance or rather than the oil displacing the air it will just compress it so the wheel moves when off the ground but not under load . The engine needs to be running as slow as possible or the pump will foam to oil before it gets to the wheel motor .
On the Z 345 I did a few weeks ago ( thanks to the help I got here ) I found I needed to spin the wheel by hand to fully purge the motor and it still took about 100 cycles F-N and 100 cycles R - N .
Over the years I have found that doing the F > R > F > R does not work as well as F > N > F > N and then R > N > R > N TO test if it is working I try to stop the wheel spinning with my heel .
And as Illingine has already said don't carry on for hours , If after 30 minutes you are not having any luck, leave it for a day & try again as frothy oil can take forever to settle back down
The other big thing is the wheels must be off the ground so they offer no resistance or rather than the oil displacing the air it will just compress it so the wheel moves when off the ground but not under load . The engine needs to be running as slow as possible or the pump will foam to oil before it gets to the wheel motor .
On the Z 345 I did a few weeks ago ( thanks to the help I got here ) I found I needed to spin the wheel by hand to fully purge the motor and it still took about 100 cycles F-N and 100 cycles R - N .
Over the years I have found that doing the F > R > F > R does not work as well as F > N > F > N and then R > N > R > N TO test if it is working I try to stop the wheel spinning with my heel .
And as Illingine has already said don't carry on for hours , If after 30 minutes you are not having any luck, leave it for a day & try again as frothy oil can take forever to settle back down
I’m assuming you’re talking about this charge port?Yes I removed it. How would I tell if it needs to be rotated 180? I didn’t see any type of marking that would indicate a direction that it needed to face
After looking at pictures taken before/during the disassembly and reinstallation I think that might be part of my problem. It’s bittersweet to see now as I’ve already given up and loaded the mower on a trailer to bring it to the shop on Monday and now my curiosity is peaked enough to pull it back off and see if that fixes it lol