IH674 hydraulic issues

[BearGap]

I am cutting hay with a borrowed IH 674 diesel tractor pulling a New Holland 489 haybine which uses a single hose for raising and lowering. I was having increasing trouble getting it to come down, although it would raise up easily, and at the very end started getting hydraulic fluid spraying from under my left foot around the hydraulic dipstick. This was following by a partial loss of power steering, but I made it back to the barn with the haybine raised and fluid all over the left side. Now the haybine won't come down, even with the tractor parked and shut down, and the dipstick shows no fluid, but there is a lot on the ground.

There are no flexible hoses under the footpad in that area, and all the fittings seem tight. Would this unit start throwing fluid if it got real low? Any ideas as to what the problem is?

 

[Janicholson]

A bad hydraulic coupler will do it. If the lift hose coupler fails it can act as a one way valve. A Control valve not centered can do it, as can a draft control system with a misplaced control lever under the cover. (best guesses from this far away) block up the machine to prevent it from crashing, then assess pressure in the hoses. Jim

 

[Highwayman]

The hydraulic filter is in the dipstick area. My advise is to refill with hydraulic oil and determine where the oil is leaking. As far as the mower not lowering try changing the tip on your hose. The springs get weak in them

 

[JimB2]

Hi Beargap when you connect a single acting cylinder with only 1 hydraulic hose to a 674 with a dual acting outlets(2 outlets) then you have to set the machine cutting height on the NH 489 haybine.

The 674 remote hydraulic lever has 4 positions Back/Up Neutral Forward/Down and Float all the way down, so when using a single acting cylinder with one hose connected in the upper rear connector then
to lift move the Remote lever to the UP position and it should return to Neutral, to Lower quickly go thru the Down position to the Float position and leave it locked in the Float position or return it to Neutral quickly going thru the Down position.
By trying to lower the single acting cylinder by only pushing the remote lever to the Down position then the hydraulic system is putting full 2500 PSI on the lower remote hydraulic hose with no were for the fluid to go and it ends up tripping the hydraulic relief valve in the MCV. Was there a buzzing sound everytime you tried to lower the haybine?
Hopefully you didn't blow an O-ring in the MCV behind the filter under the left foot rest.

 

[BearGap]

Thanks for the replies. The only place I actually saw the fluid coming out was around the dipstick and it actually was pushing the dipstick up, but everything under the foot rest is wet. This happened with the haybine down and cutting as it had been for about an hour. I had quit raising and lowering it because it would not always get all the way down unless I raised it and lowered it several times. Thanks for the description of the hydraulic control, I was not aware there were 4 positions, although it felt that way and seemed to stick at the extremes. But I am pretty sure it was in neutral when things went bad. When I went back to tedd the field (different tractor) I could see the last 4 paths in the center of the field where the hydraulic fluid was spraying out. I picked up about a bale's worth of soaked hay, but I think I'll just not rake that center part to keep any residual out of the harvested hay.

I have enough hydraulic fluid available to get it refilled, I think, but before just wasting that on the ground with more leakage is there something I can check to see if it is the MCV? How hard is it to get at that and replace the o-ring? Can I disconnect the hydraulic hose to the haybine with it stuck in the up position?

 

[BearGap]

Update: Found the problem. One of the lines was broken at the flare inside a fitting under the left floorboard, and that was spraying oil up and everywhere. A fix is underway, going to probably try to cut off the end and insert a section of flexible hose rather than trying to pull that formed metal pipe out. It took almost 5 gallons of hydraulic oil to get up on to the dipstick and I am hopeful that once repaired and up to pressure we can get the valve to work to lower the haybine.

 

[JimB2]

If an O-Ring blows some where in the MCV some function will not work, like 3pt and remotes or Brakes and Power Steering or IPTO.
To check the hydraulic/transmission oil level on a 674, park it on the level and run the engine at about 1500 RPM for 5 to 10 minutes and then check the dipstick for being above the has marks.
You can overfill by 5 gal without problems.
Be sure to clean the hydraulic oil cooler at the front of the rad and the rad.

There should be an O-Ring either at the top of the dipstick tube or on the dipstick itself that locks the dipstick in place and prevent blow by.
I am not sure what would cause the hydraulic oil to blow out the dipstick other than the pump is sucking air some where or some O-Ring has blown allowing high pressure hydraulic oil directly into Trans/Diff case.

I have included a picture of the MCV hydraulic oil flow for a 674 but your 674 will not have the Forward/Reverser option.
By using a single action cylinder on the double acting hydraulic valves by using the Down position the high pressure hydraulic oil was tripping the System Relief Valve in the bottom right of the MCV.

 

[JimB2]

OOPS, I never answered your questions:
1) To unhook the hydraulic hose from haybine in the up position I believe there is a transport lock position that you can put a pin in or a bar in place that will hold the haybine in the up position and then with tractor OFF move the hydraulic lever to float and that should release the hydraulic oil pressure.
2) Re checking for O-Ring failure, No only option is refill and see what happens but be ready to shut tractor off and BE CAREFULL of HIGH PRESSURE HYDRAULIC OIL if there is a leak, wear eye protection, gloves and protective clothing.

 

[JimB2]

Was it the bottom right HIGH PRESSURE smaller line on the MCV or the Return larger line on bottom right of MCV?

 

[BearGap]

It was the line directly under the filter. If the picture posts you can see the splice made with a short length of flexible hose and compression fittings.

 

[JimB2]

That is the older style MCV and believe the line you repaired is the power steering return line.

Usually the lines leak leak under the seat, junk gets under the deck that the seat sits on and then rubs thru a hydraulic line.