L455 loss of lift boom power after service

[foton]

i have read a similar thread which had these symptons and said either relief valve or gear pump - how do you confirm which one ? do i need to pressure test gear pump first

I would think so

 

[deaop06]

i have read a similar thread which had these symptons and said either relief valve or gear pump - how do you confirm which one ? do i need to pressure test gear pump first

Check your bucket cylinder and see if there is a pugged fitting on it. Should be close to bucket. If there is that is where you hook the pressure gage. Look up the pressure (mine was 2050 to 2200) Hook up gage, start the machine let it warm up then curl the bucket to the stop. On mine it was 1650 and I replaced the gear pump. The pressure went to 2165. The relief valve I don't know if it would cause your problem. Gear pumps are not cheap.

 

[NHL455]

Check your bucket cylinder and see if there is a pugged fitting on it. Should be close to bucket. If there is that is where you hook the pressure gage. Look up the pressure (mine was 2050 to 2200) Hook up gage, start the machine let it warm up then curl the bucket to the stop. On mine it was 1650 and I replaced the gear pump. The pressure went to 2165. The relief valve I don't know if it would cause your problem. Gear pumps are not cheap.

the only thing that made me think it was the relief valve was that it seemed to get worse when the oil warmed up making me think that it could hold a bit of pressure when the oil was thicker? i took the releif valve off and it seems to be clean and i can push the spring to open which blocks the holes it and it springs closed which opens the holes again. If i test at the boom cylinder how will i know if it is the pump or the relief valve as this is after both of them?

 

[NHL455]

the only thing that made me think it was the relief valve was that it seemed to get worse when the oil warmed up making me think that it could hold a bit of pressure when the oil was thicker? i took the releif valve off and it seems to be clean and i can push the spring to open which blocks the holes it and it springs closed which opens the holes again. If i test at the boom cylinder how will i know if it is the pump or the relief valve as this is after both of them?

also did your gear pump fail suddenly as this issue only occurred after i cleaned out the oil and replaced hydraulic filters ?

 

[deaop06]

also did your gear pump fail suddenly as this issue only occurred after i cleaned out the oil and replaced hydraulic filters ?

I don't know if it was suddenly but first indicator was lifting loaded bucket and turning at same time. Lift almost stopped and a noise on right side. I could lift and turn but not together. Plugged screen was my thought. I checked that and it was clean. With oil on full it was loss of pressure. That's when I put gage on. Check cold and got 1840. Warmed up it went to 1650. I opted to buy new not try to rebuild because dealer said most rebuilds didn't work. The gears were worn so couldn't build pressure. Was I sure about the pump? No I wasn't. You could say I made a good guess. I don't know if anyone can check the pump as I never asked.

 

[NHL455]

I don't know if it was suddenly but first indicator was lifting loaded bucket and turning at same time. Lift almost stopped and a noise on right side. I could lift and turn but not together. Plugged screen was my thought. I checked that and it was clean. With oil on full it was loss of pressure. That's when I put gage on. Check cold and got 1840. Warmed up it went to 1650. I opted to buy new not try to rebuild because dealer said most rebuilds didn't work. The gears were worn so couldn't build pressure. Was I sure about the pump? No I wasn't. You could say I made a good guess. I don't know if anyone can check the pump as I never asked.

thanks my drive left and right is fine but i think they are not related to the pump on my machine, i cannot find a replacement pressure relief valve anywhere on the internet part no. 277872 and no alternative part either as far as i can find. i have ordered a better test kit so will report back with the results