Leak Test -714670818

TM 5-2420-224-34

BACKHOE CONTROL VALVE, DIPPER AND BUCKET SECTION VALVES

R E P A I R (CONT)

Leak Test

NOTE

Perform steps 1 thru 3 to check high-pressure safety relief valves.

Stroke pump until pressure is built up to less than opening pressure of safety relief valve.

NOTE

It normally takes minimum of 15-30 seconds to bleed down to approximately 1000 psi

(68 bar).

Allow pump to sit and monitor pressure for 30-45 seconds. Pressure should have dropped to

approxirnately 500 psi (34 bar) and should not drop off to 0 for a few minutes.

If pressure drops off quicker, there is excessive leakage in circuit being tested. Check following:

Tube connections

Safety relief packings

Poppet seat in safety relief valve

Oil passing by valve spool

Valve spool not returning to neutral position

Possible cracks in backhoe control valve

NOTE

Perform steps 4 thru 6 to check low-pressure safety relief valves.

Stroke pump until pressure is built up to less than opening pressure of safety relief valve.

NOTE

It normally takes minimum of 15 seconds to bleed down to approximately 300 psi (20.4

bar).

Allow pump to sit and monitor pressure for 30-45 seconds. Pressure should not have dropped to, and

should not drop off to, 0 for a few minutes.

If pressure drops off quicker, there is excessive leakage in circuit being tested. Check following:

Tube connections

Safety relief packings

Poppet seat in safety relief valve

Oil passing by valve spool

Valve spool not returning to neutral position

Possible cracks in backhoe control valve

NOTE

Follow-on Maintenance:

Install dipper section valve or bucket section valve in backhoe control valve (page

20-79