Deere 670 Hydraulics

[Edhead]

Hello good TBN people.

Firstly, I apologize if there's already a thread on this. I seem to be having a difficult time using the search function in a meaningful way, but I did poke around a bit before posting.

I've got a Deere 670 4WD with P/S and front end loader. After about 15 years of abuse, the hydraulics began whining pretty bad and barely working (steering and loader). I assumed it was the pump, so I just swapped it out with a brand new JD unit. Unfortunately, after replacing the pump it seems the same, though not whining. Of course, I'm also not running the engine for long as I'm afraid of doing more damage. Fluid level actually seems to be a little high, did not have to add any. I am wondering if it now needs to be bled of any air that had been trapped in the lines (or pump). Perhaps I was supposed to fill the pump with fluid before I buttoned up the lines?

Anyway, and advice would be greatly appreciated.

Ed

 

[JimRB]

You changed the fluid and filter with Hy-gard and a John Deere filter? I thought I read that on my 870 that the power steering was on one pump and the loader was on another pump. Looking at the repair manual suggests this but it is late. To dark to look under the hood tonight. Pump should purge air quickly.

 

[Industrial Toys]

A gear pump is positive displacment so it "should" prime itself to some degree. Any suction leak could cause it not to.

Is the suction screen clean?

 

[Edhead]

Thank you JimB, unfortunately, I skimped on changing the fluid/filter, but certainly can. That filter is amazingly expensive. I do have 5 gallons of fluid. Yes, the P/S pump is opposite on the housing, but my understanding is that it is fed from the regular hydraulic pump. Since I lost both, I assumed that meant the hydraulic pump was the problem, and not the P/S pump.

 

[Edhead]

A gear pump is positive displacment so it "should" prime itself to some degree. Any suction leak could cause it not to.

Is the suction screen clean?

Ohhhhh, suction screen? Where is there a suction screen?

 

[Edhead]

So I am not sure what I was looking at when I priced out the hydraulic filter before, but it wasnt bad. I think it may have been the filter and the housing? Anyway, picked up 5 gallons of the Hygard fluid and the filter. Drained the fluid from filter and two lower plugs on the tranny. THen I undid the screen housing and drained from there. It turns out that my screen is in really bad shape - I'm not sure if the previous owner stuck it back in that way or if I've got a bigger problem, but I had to practically perform surgery to get it out of the housing. Its crushed on one side.

I also think that my hydraulic fluid may have bee contaminated with water from what I am seeing. A new screen has been ordered.

Any further advice? Otherwise, I will just install the screen when I receive it, tighten all of the plugs, and filler the unit to the proper level.

Any additional plugs/drain points that I should be aware of?

Thanks again.

 

[rScotty]

Usually when a hydraulic pump starts to make noise it is starved for fluid. That happens when the fluid gets contaminated with water and forms a sort of milky goo with long stringers. That goo plugs up the suction screen and just downstream of that is the suction filter which gets clogged too. So replace both of those, put in new fluid, and you should be good.

Good, that is unless you suspect or see on the dipstick that you didn't get all the contaminated fluid out of the system run some cheapy trans/hydraulic oil for a few hours - no more than 3 or 4 - and then replace the filters again and put in your good trans/hydraulic oil.

Put a cover over the tractor at night. Most trans/hydraulic fluid gets contaminated with water leaking past the shifter levers & dipstick on the floor.
Nice tractor,
rScotty

 

[Industrial Toys]

I don't know where the screen is. Usually close to the sump. I have seen them mostly able to be cleaned with solvent and replaced. Make absolutely sure, everything is assembled air tight. It can give you grey hairs is there is a slight air leak!

 

[Edhead]

Usually when a hydraulic pump starts to make noise it is starved for fluid. That happens when the fluid gets contaminated with water and forms a sort of milky goo with long stringers. That goo plugs up the suction screen and just downstream of that is the suction filter which gets clogged too. So replace both of those, put in new fluid, and you should be good.

Good, that is unless you suspect or see on the dipstick that you didn't get all the contaminated fluid out of the system run some cheapy trans/hydraulic oil for a few hours - no more than 3 or 4 - and then replace the filters again and put in your good trans/hydraulic oil.

Put a cover over the tractor at night. Most trans/hydraulic fluid gets contaminated with water leaking past the shifter levers & dipstick on the floor.
Nice tractor,
rScotty

Thank you rScotty.

Yeah, thats pretty much what happened. In my case, I believe that the water may have entered the system through a broken rubber hose for the vent on the top of the rear diff/tranny. I have a tendency to store the tractor with the seat up, to keep from getting a wet rear end. LOL. But when I saw that hose, I replaced it right away, but I have no idea how long it was that way.

A cheaper hydraulic fluid for a few hours of work seems like sound advice...as does the cover/tarp.

Thanks again!

 

[Edhead]

I don't know where the screen is. Usually close to the sump. I have seen them mostly able to be cleaned with solvent and replaced. Make absolutely sure, everything is assembled air tight. It can give you grey hairs is there is a slight air leak!

I did locate it, unfortunately its damaged. A new one has been ordered, hoping that someone just stuck it back in that way and I don't have a bigger problem than I thought. I'll be sure that everything is nice and tight - great advice.