328 Hyd pump sucking air

skidsteer.ca · Apr 13, 2012

I have a customers 328 here for some work, has @ 2800 hours, needs some pin work and tlc, but I'm more concerned about something he never really wanted fixed, but after discussing with him its clear it needs it. The hydraulic jerk on all joystick function, and the oil in the res gets foam in a heart beat after start up.
I can't see any leaks in the suction side of the system and it should leak as the pump is below the fluid lever. How common is it for the sear around the pump shaft to fail, is it usually a seal only or time for a new pump?
I have yet to dig into the manual, just wondering if anyone has any thoughts on this.
Ken

7LBSSMALLIE · Apr 13, 2012

not to many folks rember how to find a suction leak i bet old m knows i posted this on tip and tricks good old fashioned shaving cream place on suction lines , find dimple there is youre leak. seems stupid but eaisley discernable,

Tazza · Apr 15, 2012

7LBSSMALLIE said:
not to many folks rember how to find a suction leak i bet old m knows i posted this on tip and tricks good old fashioned shaving cream place on suction lines , find dimple there is youre leak. seems stupid but eaisley discernable,

Keep in mind that a restriction in the suction line can cause bubbles. My 731 with a blocked suction line filter had this problem when i first bought it.
Just another thing to look out for.
I like the idea of shaving cream for finding a leak, simple, yet effective.

skidsteer.ca · Apr 16, 2012

Tazza said:
Keep in mind that a restriction in the suction line can cause bubbles. My 731 with a blocked suction line filter had this problem when i first bought it.
Just another thing to look out for.
I like the idea of shaving cream for finding a leak, simple, yet effective.

A couple thought to try, guess I'll just have to dig into it. Routing of the suction line is a major pita, getting the pump off does not look any better.
Oh well have to get this bleeding 743 out of the shop then the X is next

Fishfiles · Apr 16, 2012

skidsteer.ca said:
A couple thought to try, guess I'll just have to dig into it. Routing of the suction line is a major pita, getting the pump off does not look any better.
Oh well have to get this bleeding 743 out of the shop then the X is next

Maybe it is not sucking air , maybe it is creating air , cavatation produced from wear on the plate of the pump a flow and working pressure test might show you something

skidsteer.ca · Apr 24, 2012

Fishfiles said:
Maybe it is not sucking air , maybe it is creating air , cavatation produced from wear on the plate of the pump a flow and working pressure test might show you something

Well picked up a flow meter from a friend, so see ho that goes, but cant see it passing the test when the supply gets all airated. Going to try running it low rpm and with no pressure (just sitting still) to see if it foam or not like this.
They have been running it like this for awhile, even had to low the res level as it was boiling out. Thinking the pump is likely dead.
Ken

Fishfiles · Apr 24, 2012

skidsteer.ca said:
Well picked up a flow meter from a friend, so see ho that goes, but cant see it passing the test when the supply gets all airated. Going to try running it low rpm and with no pressure (just sitting still) to see if it foam or not like this.
They have been running it like this for awhile, even had to low the res level as it was boiling out. Thinking the pump is likely dead.
Ken

you saying it was bubbling out the tank made me think back on something I seen really freaky happen once , it was on a 7 seried Bobcat and the screen in the hydraulic tank fill neck was gone and they had dropped a piece of hose from the bottom of a funnel into the tank and just forgot about it , it was in the supply hose and sticking up in the tank I'd guess above the fluid level and sucked in air I found while taking out the gear pump when I pulled the hose off the bottom of the tank to get it out the way -----------I doubt you'll see that , I think the pump is really trashed to boil it over with air bubbles

7LBSSMALLIE · Apr 24, 2012

Fishfiles said:
you saying it was bubbling out the tank made me think back on something I seen really freaky happen once , it was on a 7 seried Bobcat and the screen in the hydraulic tank fill neck was gone and they had dropped a piece of hose from the bottom of a funnel into the tank and just forgot about it , it was in the supply hose and sticking up in the tank I'd guess above the fluid level and sucked in air I found while taking out the gear pump when I pulled the hose off the bottom of the tank to get it out the way -----------I doubt you'll see that , I think the pump is really trashed to boil it over with air bubbles

i concur have seen this once ,on a 7 serrieries but still applicable drain and clean tank. look for obsttructions. exv dont normally suck air ,Note they are apressurizied tank for a reason . there is an air bleeding procdure if you need ill get it to you but normally youre basic work the functions will get itt out in extremes take load sense line loose at control valvve hose to tank, and run at idle till clears up tech licanily you are supposed to filter , as in part number who gives a shit. dude run a hose from load sense back to tank .run for 15 cycling all ffunctions air should bleed,

skidsteer.ca · Apr 25, 2012

7LBSSMALLIE said:
i concur have seen this once ,on a 7 serrieries but still applicable drain and clean tank. look for obsttructions. exv dont normally suck air ,Note they are apressurizied tank for a reason . there is an air bleeding procdure if you need ill get it to you but normally youre basic work the functions will get itt out in extremes take load sense line loose at control valvve hose to tank, and run at idle till clears up tech licanily you are supposed to filter , as in part number who gives a shit. dude run a hose from load sense back to tank .run for 15 cycling all ffunctions air should bleed,

#2 and # 3 section would both push 2250 psi when I bottomed the function.
#1 1500psi at idle, 2050 reved up. This is with oil @ 90f
The E seal was gone inside the pump at the back side of the first section. All sections have a ridge where the gears run in the inside outer body, but #1 is the worst.
Further this is a throw away pump, nothing but seals available as parts. $1275 will get me a fresh one at the dealer. LPS can't get them.
Doubt there is any other source?

7LBSSMALLIE · Apr 26, 2012

skidsteer.ca said:
#2 and # 3 section would both push 2250 psi when I bottomed the function.
#1 1500psi at idle, 2050 reved up. This is with oil @ 90f
The E seal was gone inside the pump at the back side of the first section. All sections have a ridge where the gears run in the inside outer body, but #1 is the worst.
Further this is a throw away pump, nothing but seals available as parts. $1275 will get me a fresh one at the dealer. LPS can't get them.
Doubt there is any other source?

good job fininding issue, after install of new pump dial in pressures to hi side of spec. you will be happy with change in performance 1 or 2 hundred psi world of differance at sticks.

Tazza · Apr 26, 2012

7LBSSMALLIE said:
good job fininding issue, after install of new pump dial in pressures to hi side of spec. you will be happy with change in performance 1 or 2 hundred psi world of differance at sticks.

That's the worst thing about gear pumps. As the bearings wear they start to chew the pump housing. The more they wear the more they eat it. You replace the bearings, your pressure drops of as the clearance between the gears and housing are wrong. Vane pumps compensate for this with the vanes just extending slightly further.
I guess its the nature of the beast. Just a shame its such an expensive repair....

skidsteer.ca · May 2, 2012

Tazza said:
That's the worst thing about gear pumps. As the bearings wear they start to chew the pump housing. The more they wear the more they eat it. You replace the bearings, your pressure drops of as the clearance between the gears and housing are wrong. Vane pumps compensate for this with the vanes just extending slightly further.
I guess its the nature of the beast. Just a shame its such an expensive repair....

After a few phone call I found a dealer that threw me a bone on some Bocat promotion coming up that offers 15% off, so got a new one for $1083
Still spendy but better.
If you need genuine parts now might be the time to hit your dealer up. Its still coming as they can't bill me tll the 11th I believe.
Still waiting for it, wlled up a slack pin hole in the main swing pivot today.
Going into the crowd pivot point next.
Ken

skidsteer.ca · May 17, 2012

skidsteer.ca said:
After a few phone call I found a dealer that threw me a bone on some Bocat promotion coming up that offers 15% off, so got a new one for $1083
Still spendy but better.
If you need genuine parts now might be the time to hit your dealer up. Its still coming as they can't bill me tll the 11th I believe.
Still waiting for it, wlled up a slack pin hole in the main swing pivot today.
Going into the crowd pivot point next.
Ken

Update
Finally got the new pump a week ago and they changed the outlet ports from orb to flange. So finally got the flanges and installed it yesterday. Had to let the trapped air out at the suction of the pump, then the pump circullated oil in the tank. Naturally full of air at first, but getting better with each run/sit cycle.
Problem is some functions have no pressure, so where is the bleeding to be done from 7lbsmallie?
Right now the tracks won't turn, even in the air, the bucket and thumb are lazy and the boom seems to lift ok (at least makes the motor labour a bit when hitting the end) but won't begin to lift the machine on the down side. Blade and crowd boom have good pressure.
I'll start looking through the manual for bleeding procedures....
Thanks
Ken

Bobcatdan · May 17, 2012

skidsteer.ca said:
Update
Finally got the new pump a week ago and they changed the outlet ports from orb to flange. So finally got the flanges and installed it yesterday. Had to let the trapped air out at the suction of the pump, then the pump circullated oil in the tank. Naturally full of air at first, but getting better with each run/sit cycle.
Problem is some functions have no pressure, so where is the bleeding to be done from 7lbsmallie?
Right now the tracks won't turn, even in the air, the bucket and thumb are lazy and the boom seems to lift ok (at least makes the motor labour a bit when hitting the end) but won't begin to lift the machine on the down side. Blade and crowd boom have good pressure.
I'll start looking through the manual for bleeding procedures....
Thanks
Ken

What is the serial number?

skidsteer.ca · May 17, 2012

Bobcatdan said:
What is the serial number?

516612xxx
Wondering if i swapped a #8 hose, but there are just the 3 pump outputs and the one to the block between #2 and #3 pump. I should have labeled them, but they where all sitting in order, the outputs with elbows pointing up and the 4th line sideways.
Ken

skidsteer.ca · May 17, 2012

skidsteer.ca said:
516612xxx
Wondering if i swapped a #8 hose, but there are just the 3 pump outputs and the one to the block between #2 and #3 pump. I should have labeled them, but they where all sitting in order, the outputs with elbows pointing up and the 4th line sideways.
Ken

Well I hooked in a pressure guage to #3 section and I got nothing, not even 50 psi. It will pump oil out the open line but appears to have minimal pressure.
Never dawned on me at the time, but while connecting the guage to the fitting oil was flowing through the pump. A gear pump should not free flow?????????
Something must be assembled wrong between section 2 and 3. This is the pump that has the check valve port block between section 2 and 3. Also 2 and 3 share a common suction hose through a port iside the pump. Where as #1 has its own inlet.

7LBSSMALLIE · May 17, 2012

skidsteer.ca said:
Well I hooked in a pressure guage to #3 section and I got nothing, not even 50 psi. It will pump oil out the open line but appears to have minimal pressure.
Never dawned on me at the time, but while connecting the guage to the fitting oil was flowing through the pump. A gear pump should not free flow?????????
Something must be assembled wrong between section 2 and 3. This is the pump that has the check valve port block between section 2 and 3. Also 2 and 3 share a common suction hose through a port iside the pump. Where as #1 has its own inlet.

back up and pump referance the s/m for checks .(punt) start from scratch. identify what pump does what? trace youre hoses as per hyd schmetaict referance the parts man for con firmation. you sound completley lost as a pro nothing is worse than a unit that is not factory. NIGHTMARE., IN THE MAKING , with history first i would have to confirm that plumbing is correct,(hopefully you went with oem hoses that have part #s stamped in fittings,. if not well . back to scratch it can be done. . jimmy joe blow hack jobs, are not in youre favour, at 9745 an hr fixing hacks gets expensive.. oem parts hoses etc have # stamped on fitting. can be traced this way. if one hose outa 45 is wrongly plumbed (easliy done) world of hurt.

skidsteer.ca · May 18, 2012

7LBSSMALLIE said:
back up and pump referance the s/m for checks .(punt) start from scratch. identify what pump does what? trace youre hoses as per hyd schmetaict referance the parts man for con firmation. you sound completley lost as a pro nothing is worse than a unit that is not factory. NIGHTMARE., IN THE MAKING , with history first i would have to confirm that plumbing is correct,(hopefully you went with oem hoses that have part #s stamped in fittings,. if not well . back to scratch it can be done. . jimmy joe blow hack jobs, are not in youre favour, at 9745 an hr fixing hacks gets expensive.. oem parts hoses etc have # stamped on fitting. can be traced this way. if one hose outa 45 is wrongly plumbed (easliy done) world of hurt.

The brand new pump I have makes no pressure on sections 2 and 3. I removed the guage from the from the line conected to the test port on #3. On the starter it won't even lift the oil up to run out the open hose back into the top of the hyd fill. With the engine runniing I can hold back the flow coming out of this hose with my thumb, maybe 5 psi. (not flying out the line like its going to empty the tank in 60 seconds) No wonder my guage with the 1st graduation at 100 psi won't even wiggle the neeedle.
Guess its time for another new pump. Haldex must not test these??
Smallie, I hear you, but I drove this thing in the shop and it basically worked other then foaming the oil. The only hoses that have been off are the 6 on the pump. 2 suctions you can't screw up, 3 outputs, #8 jic F with 90's up from below, and the check valve line that comes in from the top, also #8 90. But if the pump makes no flow it does not matter what line you hook to it.
Ken

Bobcatdan · May 18, 2012

skidsteer.ca said:
The brand new pump I have makes no pressure on sections 2 and 3. I removed the guage from the from the line conected to the test port on #3. On the starter it won't even lift the oil up to run out the open hose back into the top of the hyd fill. With the engine runniing I can hold back the flow coming out of this hose with my thumb, maybe 5 psi. (not flying out the line like its going to empty the tank in 60 seconds) No wonder my guage with the 1st graduation at 100 psi won't even wiggle the neeedle.
Guess its time for another new pump. Haldex must not test these??
Smallie, I hear you, but I drove this thing in the shop and it basically worked other then foaming the oil. The only hoses that have been off are the 6 on the pump. 2 suctions you can't screw up, 3 outputs, #8 jic F with 90's up from below, and the check valve line that comes in from the top, also #8 90. But if the pump makes no flow it does not matter what line you hook to it.
Ken

My two cents: even if I did not work for a dealer, something as major as a pump I would only get a factory replacement. A lot of this stuff is built to OEM spec and even thought the basic same pump is used on brand A and B, there are likly differenc one can't see. Bobcat is veray good at using say size 5, 4 and 6 are common as dirt and 5 just don't exist outside of Bobcat.

328 Hyd pump sucking air

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