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I’m looking for the procedure to prime the hydrostatic on a…

Hi I’m looking for the...
Hi I’m looking for the procedure to prime the hydrostatic on a 773 Bobcat skid steer, serial number###-##-#### Customer blew a drive motor hose and lost most of the oil. Thank you
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Answered in 5 hours by:
6/2/2021
Mechanic: Fieldtech59, Shop manager replied 1 year ago
Fieldtech59
Fieldtech59, Shop manager
Category: Construction and Road Equipment
Satisfied Customers: 202
Experience: Construction equipment repair technician since 1986, JLG certified, Shop manager since 2006.
Verified

Greetings, the 773 was a G series machine. On those machines the hydraulic system isn't a "return to tank" system, rather, it's a loop system, oil leaves the charge pump and goes to the main control valve, if no loader functions are being used oil leaves the main control valve and goes to the drive pumps to charge the pumps for drive, which the drive system is another loop system between drive pumps and drive motors. Excess oil being delivered to charge the drive pumps is dumped by the drive pump charge pressure regulating valve to the oil cooler, the hydraulic filter and right back to the charge pump to start the process all over again. The reservoir tees into the inlet of the charge pump to add oil or dump oil as required by the loader cylinders extending and retracting. With this system, there's no way to prime the hydrostat drive pumps or manually purge air from them. The only way to purge the air from the drive pumps is start the engine, let it run at idle and cycle the loader arms up/down while working the bucket tilt up and down. This will move a small amount of oil in and out of the reservoir pushing some of the air bubbles into the tank and drawing oil back into the system. While you're doing this the charge pressure regulating valve will be purging air from the drive pumps. After running and cycling the cylinders for a few minutes begin driving the machine forward at idle putting minimum load on the motors while continuing to cycle cylinder in and out. It will take some time but the air will eventually purge back to the reservoir doing this.

Fieldtech59
Fieldtech59, Shop manager
Category: Construction and Road Equipment
Satisfied Customers: 202
Experience: Construction equipment repair technician since 1986, JLG certified, Shop manager since 2006.
Verified
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Customer reply replied 1 year ago
Nice! Much appreciated! That’s great!! Thank you again! Have a great day
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Fieldtech59
Fieldtech59
Fieldtech59, Shop manager
Category: Construction and Road Equipment
Satisfied Customers: 202
202 Satisfied Customers
Experience: Construction equipment repair technician since 1986, JLG certified, Shop manager since 2006.

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