John Deere 670 with weak hydraulics

[RustyShackleford]

My old (at least 20 years) John Deere 670 Compact Utility Tractor has gotten to where the hydraulics are quite weak. In particular, the Model 60 loader (bucket with tilt and lift) has gotten much weaker than it used to be.

I'm wondering how to fix the problem. Is it likely I need a new hydraulic pump ? There's a new after-market one available here:

https://www.fridayparts.com/hydraulic-pump-am876753-for-john-deere-tractor-3005-4005-670-770-790-870-970-1070

... but I wonder how good its quality is, and how difficult to replace ?

Other factors such as pump adjustment or clogged filter ?

I'm clueless here, and would appreciate anyhelp.

 

[oldnslo]

The first thing to check is the Hydraulic pressure to see what it is vs what it is supposed to be. Then if lower than specified start diagnosis to determine if simple as the relief requires adjustment or something more serious.

Does it lift slower than it used to when empty?

 

[gstrom99]

My old (at least 20 years) John Deere 670 Compact Utility Tractor has gotten to where the hydraulics are quite weak. In particular, the Model 60 loader (bucket with tilt and lift) has gotten much weaker than it used to be.

I'm wondering how to fix the problem. Is it likely I need a new hydraulic pump ? There's a new after-market one available here:

https://www.fridayparts.com/hydraulic-pump-am876753-for-john-deere-tractor-3005-4005-670-770-790-870-970-1070

... but I wonder how good its quality is, and how difficult to replace ?

Other factors such as pump adjustment or clogged filter ?

I'm clueless here, and would appreciate anyhelp.

Fluid, filter (and screen - if equipped) change/flush first. Then check pressure.

 

[rScotty]

Fluid, filter (and screen - if equipped) change/flush first. Then check pressure.

First things first. For hydraulics, the first thing to do on many small Japanese tractors from that era is to clean the wire screen in the transmission sump. Yamar/JDs especially.

 

[5030]

Begs to ask... In 20 years have you ever changed the fluid or filters??

 

[RustyShackleford]

The first thing to check is the Hydraulic pressure to see what it is vs what it is supposed to be.

Does it lift slower than it used to when empty?

Ok, need to get some kind of pressure gauge. Where's a good point to attach the gauge ?

I think it does not lift slower; just can't pick up nearly as much weight.

Fluid, filter (and screen - if equipped) change/flush first. Then check pressure.

First things first. For hydraulics, the first thing to do on many small Japanese tractors from that era is to clean the wire screen in the transmission sump. Yamar/JDs especially.

So it doesn't have a replaceable filter like an oil filter ? Dunno if it's Japanese, but sounds like it probably is. This looks like a spin-on hydraulic filter: Fits John Deere 650 670 750 770 790 850 870 950 970 990 RE27284. But looking at the service intervals (see attached file) it looks like it doesn't.

Begs to ask... In 20 years have you ever changed the fluid or filters??

Uh, I think not, but let me check.

Thanks, guys !

 

[RustyShackleford]

I actually located a 1000-page service manual ! Too big to attach here, even the section on hydraulics.

One question though: they keep talking about the SCV (selective control valve). My tractor has a lever that you can move in four different directions, to raise and lower the bucket, and to tilt the bucket back and forth. That means I *do* have an SCV, right ?

 

[JimRB]

1989-1997 were the production years. Produced in Japan by Yanmar. On my 870 that metal screen is before the metal can filter. You might be amazed at how much junk is in that screen. The small owners manual should have to how to remove info and also mention if you have a can filter. When I say can filter I mean a filter that looks like an oil filter. On my tractor the oil filter and screen are under the left foot panel.

I replace lift arm seals. They fell apart. Not much power when seals are leaking internally.

 

[gengine]

@RustyShackleford Your SCV('s) are the hydraulic ports for 3pt attachments on the rear of the tractor, if equipped. If one of those control levers on the side console are not in neutral, you are losing pressure for your loader. It will be separate lever than your 4 position lever for your loader. It is possible it was used to run your loader, but not likely on that new of a unit.

 

[RustyShackleford]

There's a another sliding lever to the right of the seat that raises and lowers the rear 3-point hitch.

 

[gstrom99]

So it doesn't have a replaceable filter like an oil filter ? Dunno if it's Japanese, but sounds like it probably is. This looks like a spin-on hydraulic filter: Fits John Deere 650 670 750 770 790 850 870 950 970 990 RE27284. But looking at the service intervals (see attached file) it looks like it doesn't.

The filter to change, is #5 in your parts list. There should also be a metal screen to take out and clean. The "trans" oil is used for all hydraulic functions. The service manual will show this process.

 

[RustyShackleford]

The filter to change, is #5 in your parts list. There should also be a metal screen to take out and clean. The "trans" oil is used for all hydraulic functions. The service manual will show this process.

That's super-helpful to know the tranny oil and hydraulic is all one system, thanks.

So, how do you get the metal screen out ?!? Looks like lots of crap has to be removed. Except, looks like there's a cover at the far end of the suction line connection (so on the right-hand side of the tractor) and you just remove that (and maybe one little suspension piece) ?

Guess I'll buy a new filter, replace that and the oil (I assume the oil all dumps out when I remove the screen). Can't find a part# for the screen so just clean that I guess. And go from there.

P.S. Mis-spoke earlier, the bucket DOES move slower than it did, even when un-loaded.

 

[gstrom99]

So, how do you get the metal screen out ?!?

The manual will show that. On my 855, I believe it's at the back, behind the "suction" hose connection.

 

[RustyShackleford]

The manual will show that. On my 855, I believe it's at the back, behind the "suction" hose connection.

I downloaded a couple of good documents. I guess we don't have a file repository here though.

 

[RustyShackleford]

Anybody have a clue what a clutch R&R would cost on this tractor ?

 

[qualsite]

My inlet screen had more debris on it that I want to admit and was collapsed. I flushed the system and replaced it with a larger inlet screen [same filter mesh, but larger length and diameter], using a bushing to step up to the large pipe thread size. There was plenty of room in the reservoir to accommodate the larger suction screen. I also added a Hycon/Hydac spin-on return-line filter with a gauge on it.

 

[RustyShackleford]

... using a bushing to step up to the large pipe thread size.

What's this about pipe threads ? This all my manual has about the screen ...

 

[rScotty]

What's this about pipe threads ? This all my manual has about the screen ...

All the Japanese tractor manufacturers came up with different setups to access that cleanable screen type suction filter. Some didn't even include that feature - although most did.
My guess is the cleanable screen crud flter itself on modern compacts is a holdover on some from the earlier tractor designs from the 1970s&80s when that feature was common to all small 4wd imported tractors.

The filter covers can be located low down or underneath and on either side of the common transmission/hydraulic fluid sump. It varies. A few didn't have it at all. A triangular cover having three bolts is a pretty common way to identify the removeable filter cover - as your photos show. That weird triangular 3 bolt cover seems to be a common feature on Yanmars and also on the tractors Yanmar made for JD.

There is a non-critical cover gasket under the cover. Most folks either make one or use RTV...or both.

BTW, is the manual you are using specific to the 670? Or something more general? The photos you posted seem to be two different sites for that same cover. Some of the imports did had the cover back by the PTO or near the draw bar.

Like "qualsite" says, the screen is commonly found to be covered with crud and/or smashed. Straighten it out and reuse. The screen usually fits loosely over a couple of projections. It is not a fluid-tight fit at all. You can make your own with 200 mesh stainless steel hardware cloth from Ace hardware, or even sew on patches with stainless steel thread.

I've never seen or heard of the cover or insides screen fitting pipe threads, nor one where the cleanable screen had enough entry clearance so the filter could be changed in size. My guess is that qualsite's tractor is different from typical Yanmar/JD. Or maybe his had been modified before.
Luck,
rScotty

 

[RustyShackleford]

That weird triangular 3 bolt cover seems to be a common feature on Yanmars and also on the tractors Yanmar made for JD.

BTW, is the manual you are using specific to the 670? Or something more general? The photos you posted seem to be two different sites for that same cover.

It's specific to the 670 AND the 770. Mine looks exactly like the lower photo (in the image I attached) - the 3-bolt cover with the drain plug in the middle of it.

I hope I'm not wasting my money changing the hydraulic fluid - guess I'll see how the screen looks. The tractor is actually owned by my landscaper neighbor, and he lets me use it for working on it and chipping in for repairs. He's not very good about keeping track of things; he thinks a 500-hour service was done at some indeterminate time in the past, and he's not sure what they actually did (specifically the screen).

 

[rScotty]

It's specific to the 670 AND the 770. Mine looks exactly like the lower photo (in the image I attached) - the 3-bolt cover with the drain plug in the middle of it.

I hope I'm not wasting my money changing the hydraulic fluid - guess I'll see how the screen looks. The tractor is actually owned by my landscaper neighbor, and he lets me use it for working on it and chipping in for repairs. He's not very good about keeping track of things; he thinks a 500-hour service was done at some indeterminate time in the past, and he's not sure what they actually did (specifically the screen).

Sounds like you are good to go. No reason in the world why you cannot carefully decant the hydraulc oil into a clean container, strain it, and reuse it - just as long as it is still clear oil and has not gotten all milky with water.

BTW, I just realized I still have a JD ops manual for the 870/970/1070. Right there on the 500 hr service pg 93 is yet another picture of the screen cover. Hard to tell just where the cover is from the picture, but it is clearly in yet a different place from yours.

The manual says to "pull the screen and clean in a safe solvent".
The JD 870/970/1070 models also have a spin-on throwaway cannister style transmission/hydraulic filter in series on the suction side. But it is the screen that always causes fluid starvation problems because of not having a bypass valve.
rScotty