NH 757C Slow Hydraulic Movement

[Powerhorse]

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]

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

 

[wdchyd]

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

 

[Powerhorse]

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]

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

 

[jinman]

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]

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]

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]

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.

 

[wdchyd]

............... and there is a sound of rushing fluid...............

Northern Industrial Mechanics Stethoscope | Automotive Diagnostics| Northern Tool + Equipment

 

[J_J]

What he heard, the rushing sound, was probably the valve relief going off.

I would be interested in the pressure while using the bucket to just open and close with no load..

It takes very little pressure to just move the bucket, but if digging causing a load, then the pressure will increase with more load until the relief goes off.

You can easily see that on the hyd gage in conjunction with a sound.

 

[Powerhorse]

J_J,

I got the replacement hoses today but most likely will not get to work on it till the weekend. Work keeps me running. The supply and return hoses are connected to a block which is also tied to the loader control valves. This is a factory setup from New Holland. The rushing sound was at the bucket cylinder not at the control valves like when under load. I'll post a pic of the block tomorrow sometime.

Thanks for your help

 

[Powerhorse]

Forgot to add the hoses on the BH are original. NH went with 1/4 for some reason.

 

[RickB]

Forgot to add the hoses on the BH are original. NH went with 1/4 for some reason.

Just about any BH fitted to a CUT has 1/4" hoses. A very few might use 3/8". None that i am aware of use 1/2".

 

[Powerhorse]

The supply and returns are 1/2". I figure NH did this for volume when operating more than one function at a time. I took these pics this morning. I'm wondering if the fitting with the 3 on it isint the issue as it looks double crimped....

 

[wdchyd]

It's pretty obvious someone doesn't know how to crimp hoses.....I'd be leary of all of those, you may need to check them all for overcrimp

Don't forget on a 1/4" hose fitting the inside dia of the hose fitting is 1/8" or less due to the stem wall thickness....not much room for error

 

[J_J]

Try putting a 1/4 rod through the fitting and hose. Probably can't, closer to 3/16 in.

Everyone should know why you try and match hose size with the GPM's, and we know why loaders, BH, and anything you want to reduce the speed of operation, you use smaller hose or restrictors.

The 1/4 in hose and fittings also cost less.

If you switch hoses around, you can tell if a hose is restricted more than it should be.

Make them fix what you don't like.

 

[RickB]

I should have been more concise, I meant 1/4" hoses between the valve and cylinders.
Those hoses appear to me to be overcrimped; #3 especially, but also #4. Just an observation from a guy that makes Weatherhead Hoses using 425 series hose.