Need Help On ASV SR-80 - Hydraulic Gurus PLEASE HELP

[sepulchral]

Please help.. My friend and I are beyond lost. Heres the story:

Bought a Project ASV PT-80 from a dealership for a good price ($12k) fully loaded with high flow and AC. They said it had electrical problems and provided a new complete wiring harness with it.

Checking pressures with the harness installed, i realized the tandem pump was not putting out any pressure (0psi) when it should be 218psi on standby with engine at idle. The engine-driven charge pump which supplies the motive pressure for the pilot controls was at a solid 450psi as it should have been.

Turned out both bolts to from the engine mounting plate to the tandem pump snapped and the output shaft on the tandem pump ground down to nothing. This meant the motor was not turning the tandem pump at all. ASV things maybe that the machine jumped a rock or landed hard to cause that.

My friend and I ordered a new pump shaft and bearing and seal from Rexroth and replaced the shaft on the tandem pump, following the service manual. Upon internal inspection of the tandem pump pieces, everythign looked fine.

The night we connected everything, refilled with recommended hydraulic fluid, the machine started, and moved under its own power like a charm. Even operated loader arm. Tandem pump read 218psi as it should after the repair.

Next morning the machine would not move or work. Charge pressure was now at 100psi instead of 450psi and tandem standby pressure was still at a good 218psi. SO basically the machine will not operate with a charge pressure that low.

ASV told us to cap drive motors to see where pressure is being lost - did nothing for us. WE also checked to make sure the charge relief (475psi) was not hung open and it was fine. Really pissed off and confused and wondering what to do next. ANy advise would be helpful.

WE did pull apart the charge pump and noticed some irregular wear (pic attached) but ASV did not believe that coudl cause such a pressure drop... I have no clue.

From my belief, possible causes could be one of the following

• charge pump took a ****. Do not understand how it works or if that groove could have caused such a bad pressure loss. With it running, there is no noise or vibration
• tandem pump has internal bad seal or something or took a ****
  
• pilot gen block is leaking internally

This is CRAZY i do not know why it would work fine and 8 hours later not work at all and lose 350psi charge pressure overnight.

 

[lantraxco]

Your 218 psi pressure is actually coming from the loader pump on the rear of the tandem, that's the auxiliary circuit standby pressure, has nothing to do with the drive, and was previously zero because the pump wasn't being turned.

Where are you checking charge pressure, test port A at the rear left of the engine compartment just inside the loader arm tower?

Not sure exactly how it all works but that machine has a seat switch and a seat belt switch, all part of the safety system. Might be related to this problem or not. Probably need to reassemble the charge pump and get your local hydraulic shop to flow test it, should be 15.4 GPM @ 2600 rpm, and 475 psi.

 

[sepulchral]

Your 218 psi pressure is actually coming from the loader pump on the rear of the tandem, that's the auxiliary circuit standby pressure, has nothing to do with the drive, and was previously zero because the pump wasn't being turned.

Where are you checking charge pressure, test port A at the rear left of the engine compartment just inside the loader arm tower?

Not sure exactly how it all works but that machine has a seat switch and a seat belt switch, all part of the safety system. Might be related to this problem or not. Probably need to reassemble the charge pump and get your local hydraulic shop to flow test it, should be 15.4 GPM @ 2600 rpm, and 475 psi.

Yes using test port in engine bay

I have another Asv with same charge pump. We are going to swap out pumps to see what happens

 

[lantraxco]

Good idea, let us know what happens.....

 

[Shanedoesnt]

Posi power relief valve has popped the snap ring and is bypassing the charge pressure. These are the most ridiculously overpriced parts I've ever seen. The price is about the same as a rebuilt tandem pump. Therefore many times people get the rebuilt tandem pump and send them a perfectly good pump as a core. When it works again no one ever questions the posi power relief valve. Which is just a regular relief valve that is so overpriced that they have ruined the reputation of these machines.

 

[Arny L]

Yes using test port in engine bay

I have another Asv with same charge pump. We are going to swap out pumps to see what happens

Strictly speaking pumps, I was always told if you can feel wear with finger nail, its time to replace.

 

[Shanedoesnt]

Bet you have the same results. Posipower relief valve in the tandem pump is the fault. If it's a two speed most likely. What happens is you have it moving along in high speed which is about 6 miles per hour faster than any other ctl and the ground wire loses it's connection or you accidentally hit the down shift trigger and,.. pop!! There went your main relief valve or posi power valve as they call it. Technically the valve did it's job but the inner snap ring that holds the brass seal or bushing rather in place got knocked out of it's groove and the brass bushing is loose and it sometimes takes a bit to get it out of position and there goes the charge pressure. Believe me. I have been down every path to get this knowledge and I will be damned if I let anyone else go through the trouble that I did only to find that the aftermarket part retailers are ripping people off. Sending you down every avenue to sell you parts. If you are losing charge pressure you should start with the main relief valve in the center of the four other ones that give the Rex Roth tandem axial pump it's distinctive look. Thank me for saving you the money they would have let you waist if I am right. Then ask me what you have to do to fix it or where you can get one of them for $160 dollars instead of the $2800 Track Loader Parts sells them for. Remember that Rex Roth pump was sold under a different name. Cat!!

 

[Shanedoesnt]

Bet you have the same results. Posipower relief valve in the tandem pump is the fault. If it's a two speed most likely. What happens is you have it moving along in high speed which is about 6 miles per hour faster than any other ctl and the ground wire loses it's connection or you accidentally hit the down shift trigger and,.. pop!! There went your main relief valve or posi power valve as they call it. Technically the valve did it's job but the inner snap ring that holds the brass seal or bushing rather in place got knocked out of it's groove and the brass bushing is loose and it sometimes takes a bit to get it out of position and there goes the charge pressure. Believe me. I have been down every path to get this knowledge and I will be damned if I let anyone else go through the trouble that I did only to find that the aftermarket part retailers are ripping people off. Sending you down every avenue to sell you parts. If you are losing charge pressure you should start with the main relief valve in the center of the four other ones that give the Rex Roth tandem axial pump it's distinctive look. Thank me for saving you the money they would have let you waist if I am right. Then ask me what you have to do to fix it or where you can get one of them for $160 dollars instead of the $2800 Track Loader Parts sells them for. Remember that Rex Roth pump was sold under a different name. Cat!!

Bet you have the same results. Posipower relief valve in the tandem pump is the fault. If it's a two speed most likely. What happens is you have it moving along in high speed which is about 6 miles per hour faster than any other ctl and the ground wire loses it's connection or you accidentally hit the down shift trigger and,.. pop!! There went your main relief valve or posi power valve as they call it. Technically the valve did it's job but the inner snap ring that holds the brass seal or bushing rather in place got knocked out of it's groove and the brass bushing is loose and it sometimes takes a bit to get it out of position and there goes the charge pressure. Believe me. I have been down every path to get this knowledge and I will be damned if I let anyone else go through the trouble that I did only to find that the aftermarket part retailers are ripping people off. Sending you down every avenue to sell you parts. If you are losing charge pressure you should start with the main relief valve in the center of the four other ones that give the Rex Roth tandem axial pump it's distinctive look. Thank me for saving you the money they would have let you waist if I am right. Then ask me what you have to do to fix it or where you can get one of them for $160 dollars instead of the $2800 Track Loader Parts sells them for. Remember that Rex Roth pump was sold under a different name. Cat!!

Like money bag says I don't trust nobody.