NH 757C Slow Hydraulic Movement

Powerhorse · Jul 4, 2013

Hey everybody,

A few weeks ago I was using my backhoe to move my shed and had a hydraulic hose blow on the boom. I decided to replace all the hoses on the boom, dipper and bucket cylinders. I took all 6 hoses off and capped the cylinders and valves to keep oil from leaking out. I took the hoses to a hydraulic hose shop and left them with the shop so they could duplicate them. I got them back the other day and installed them today. Now for my problem. I seem to be having an issue with the bucket curl and dump moving very slow and have a fluid rushing sound and the cylinder. I had the same issue with the dipper but that seems to have worked itself out. The bucket is faster to curl then dump but both directions are slower than before. I have cycled all the cylinders from end to end. I loosened and checked the fitting on the bucket cylinder with the rushing sound and didn't see any issue. I reconnected the fitting and the problem continues.

The hose shop used 1/4" or 6.4mm 3000 psi hose with Eaton fittings that matched my hoses. All other hydraulics seem to work fine. Any ideas on this would be appreciated.

Thank You

RickB · Jul 5, 2013

1/4" hose is not difficult to overcrimp if assembled with a crimper lacking a positive stop.

wdchyd · Jul 5, 2013

^^^^^What he said.....I've seen it too

Powerhorse · Jul 5, 2013

Thanks for the responses guys. I was thinking that but was kinda hoping it was an air in the sysyem issue. I know they are self bleeding systems though. I contacted the hose shop and they said they would remake the hoses for that cylinder. Not looking forward to taking all that apart again. Hopefully I can fish the hoses through the boom without removing the boom cylinder again.

J_J · Jul 5, 2013

Why not so a flow test in a 5 gal bucket.

jinman · Jul 6, 2013

J.J., I'm going to disagree with you here. I think the OP's "real-world" flow test is his backhoe. If all he did is replace hoses and that slowed operation, what would a flow test into a 5-gal bucket tell him except a set of numbers? My point is that his backhoe is slower than before and there is a sound of rushing fluid. Since he only changed hoses, I think his problem is isolated already. I'm not trying to pick a fight or be argumentative, just stating a differing opinion and my reasoning.

Powerhorse · Jul 6, 2013

I think what I'm going to try at this point is disconnecting the new hoses on the bucket cylinder and connecting the old hoses outside of the back hoe just to try it. This will tell me for sure if its the hoses or crap in the system possibly from the new hoses. I should have a replacement set of new hoses on Monday for the bucket cylinder. I think I'll wait till I have everything and do it all at once. Thanks for the help so far guys I'll keep you posted on the outcome.

J_J · Jul 6, 2013

Whatever the pump flow is, that flow should pass through the BH hyd circuit , and if you know the tractors pump flow, then whatever fluid comes out of the BH hoses would represent the tractor flow.

The 1/4 in hose might provide some restriction, but should not be much.

So if the tractor flow is 10 GPM, and you are only getting 8 GPM out of the BH hoses, that is not bad considering the smaller hose.

If the BH hoses is only flowing about 5 GPM, then I would suspect a restriction somewhere else.

More flow checks should be performed through the hyd system to find the restriction.

Another check, is there equal flow from both work ports?

Unless you have a flow meter, the bucket flow test will work.

If you push the joystick at about a 45 degree angle, you are now splitting the flow and using two spools. The speed of operation on both component will slow.

J_J · Jul 8, 2013

What was the outcome of the hose remake?

Do you still think the BH is slow?

Is the BH fluid coming directly from the PB on the FEL valve,or hyd block or using a rear hyd outlet and bungeed lever to make it work.

The hyd nomograph I have says use 1/2 in hose used unless you want to restrict the flow to slow the cyl speed.