JD 690B-how to check and set relief valves

[jacks]

I need to check my relief valve settings. It has gradually lost some lifting power over the years. The procedure is not covered in the factory service manual. What sequence should be followed? Thanks, jack
 

[J. Schwiebert]

Have you put a gauge in the circuit and checked to see what pressure you have now?Can you "deadhead" a cylinder and blow the relief valve?
 

[Roy Suomi]

On the boom cylinder plumbing , right at the cylinder tubes, you will find "Tees".. If you plumb in a guage at the tees and dead head the oil circuit , the reading you will get is the lowest relief valve setting of the combined flow oil circuits - OR - the fact that the pump is worn to the extent that it won't produce enough pressure to pop off the relief valves..
 

[jacks]

Thanks Roy and John. With the boom lift cylinder deadheaded, is it only the relief valve for that circuit that determines the relief pressure? Could any one relief valve that is relieving at too low of a pressure effect all of the circuits?
 

[Roy Suomi]

Sure...You bet it can.. My test will only show the lowest relief valve setting.. There are a gammit of relief valve tests..There are circuit relief valves and main reliefs that need to be set. If you know someone that can read your flow/pressure readings with a flowmeter, that would eliminate a worn pump..Usually relief valves don't change unless a spring looses it's tension. Then even after resetting the relief it can return to a lower setting due to a spring weakening..
 

[Roy Suomi]

My 690-B manual has the procedure for testing pressures, I don't know why yours doesn't.It is a long drawn out affair..If you follow the procedure by the book, it should work out right..