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784 Hydraulic Whistle


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November of last year I picked up a 784 Utility that didn't run for the last couple of years but claimed it was running when parked.  When I saw it, I knew it had to run and was a good deal ($1500) with straight sheet metal, 6 front weights, and a set of rear weights plus ballasted rear tires.  So I took a gamble and got a friend to haul it home.  A new battery, front tire, unclogging the fuel cutoff, and bleeding the injectors got her running.  Hours show 3413 on the none working meter.   I changed all the fluids and filters, got the PTO lever unstuck and the PTO works, plus got the diff lock lever unstuck but when you use it, can't get it back up unless you pull it with your hand (still need to work on the lever).  The T/A works, brakes work, and 3 point works as well.  From the info on this site I was able to adjust the kill lever on the fuel pump to stop it from running rich and being fumy.  Took the home made trampoline hoop canopy off and found a set of factory ROPS plus canopy and put new seat cushions on.  For the last few months I only used it to take the kids for a ride and run it just to tinker getting things working.  The engine runs like a top with no blow by or oil usage and the clutch is strong.  I need to fix the lights, sticky throttle lever, fuel, and temp gauge.  I'm not sure how many dummy lights work other than the alternator.  Oh, and of course the parking brake doesn't work.

This spring I sprayed my pasture and after an hour or so, I noticed a high pitch whistle that you could only hear while idling.  It is not a whine but a whistle.  I couldn't figure out  what it was and finished spraying.  Noticed the ever so slight wetness of a seeping seal on the left 3 point arm on the rocker shaft.  I chalked it up to not being used in a while.

Took it for an hour road trip to my dad's to pick up a Hay King 6 shank renovator (don't have a trailer wide enough to put it on)  and noticed the 3 point seepage was back plus some leakage out of the 1k PTO shaft and the dipstick was popped out of the tube.  Unscrewed the breather and it shot into the air a few inches and was clogged.  I took it apart, cleaned the screen, put it back on and headed home.  Unscrewed the breather again and I couldn't blow through it.  So I got a new one and added about 4 more gallons of hydraulic oil because I read here that overfilling is recommended.  Got my JD709 shredder working (another cheap ($500) but high potential project) and after 30 minutes to an hour, the whistle is back but no seepage from the seals.  The new breather is clogged up again and again I cleaned it out.  Checked from the fill up plug with a flashlight and I can see oil being sprayed back into the rear end housing.  All hydraulics work except at idle when the whistling is going on, the 3pt won't lift.  Give it 50-100 rpm off of idle and it lifts just fine.  When cold, it lifts fine at idle.  Now the left brake needs bleeding.  I was spraying at 1600 rpm and shredding at 1800 rpm.  On the road trip I only ran 2500.

Do I need to pull the springs and valves out of the MCV and possibly unloader valve to see if they are dirty?  Any idea why the breather keeps clogging up to the point I can't blow thru it?  I think the whistle is coming from the MCV but I'm not 100% sure.  I planned on going ahead and putting another new hydraulic filter and new fluid just because I figure it may have got some dirt or slight rust broke loose from running.  Also, when I changed the fluid originally, it looked fine and I was surprised it wasn't milky.

Pictures are how she looked when I got her, a good view of the homemade canopy w/shredder, and now.

Thanks,

Jason

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Hi Jason, I can't help specifically with your whistling problem, but have a question that if you can answer them may help in troubleshooting...

What does the breather keep getting clogged with? If you're cleaning it out certainly you're getting "stuff" out of it. What kind of "stuff" is coming out?

The rear end getting pressurized to the point you describe does not sound right to me. That sounds like it is sucking air from an external connection somewhere.

Also, the "overfilling" thing is a nasty rumor that just keeps getting perpetuated as a cure-all for hydraulic problems. It does not even apply to this series of tractors, at least I've never heard of overfilling what I call the "Doncaster Utility" tractors. It applies to the large frame row crop 06, 56, 66, 86, and 3x88 series tractors, and only for one specific problem. I don't think there's any harm in it, but it's generally not a fix for anything.

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Has the Hydraulic oil and filter been changed yet ? you may have a high pressure leak on the rockshaft lift cylinder area  making the noise and losing pressure 

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Good to know about overfilling the hydraulic system.

The breather show no discernible particles but the fine screen has a general brownish color.  I will say that when you remove the breather while the whistling noise is occurring, it does not go away.

The hydraulic oil and filter has been changed when I first got her running.  I was going to change them again along with the fuel filters and oil filter just because it set for a while and I have used about 2 tanks of fuel.

Also, the 3pt does not leak down and the draft control works.

Is there a possibility I put the filter cover on wrong and I'm not getting a good seal allowing it to suck air?  I'm just shooting in the dark.  It's a solid tractor other than this noise and I want it to get it fixed before it causes something else to fail and turns into a major repair.

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Congratulations on your steal!  You got a good deal, and I think the tractor looks to be in good shape.  The non matching tires would drive me nuts!  OCD I guess.

 

On your noise, I suppose it is possible it is sucking air and that is causing your noise.  Does the steering work when it is whistling? Also the fact you say the brake needs bled is also another indication that air is entering the system, unless the brakes are leaking.  I think that is where I would start.  You did install a new o-ring in the groove for the filter cover right?  If not, change that whengine you change the filter.

As far as the vent plugging, it sure sounds like it has excessive moisture in the oil that is venting out.  You say this needs the parking brake fixed.... well, you are going to be taking the rockshaft cover off to fix that.  Why not down the tractor, take the top off and have a look inside, and maybe flush it out while you are in there.  Might find the source of the goo, and get your brake fixed.  That is what I would do. 

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Hi Jason, nice 784, I have spent many hours in the seat of a 684 and the smaller 454. 
Do you have manuals?
Add a little 2 cycle engine oil to the Diesel tank everytime you add fuel to lube the Bosch injection pump.
Re overfilling hydraulics it does not hurt anything and helps on an older tractor when the transfer pump gets weak and can't keep the hydraulic fluid level maintained between the 3 chambers in the trans/diff of these tractors especially on hilly terrain. 
Proper method to check trans/diff/hydraulic fluid level is to park tractor on the level, run it for about 5 minutes at about 1200 RPM and then check the dipstick level. This allows the transfer pump to even out the fluid between the chambers. This is the reason for 3 drain plugs to empty all the different chambers.

Re Whistling noise, when you hear it, reach down by the hydraulic filter and feel the filter housing for vibration and feel the two steel lines on front and rear of MCV for vibration as well.
Be sure to chock your wheels or have a 3pt implement sitting on the ground as your parking brake does not work.
What happens if you dead head the remote hydraulic outlet? 

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I agree, that is an real nice find and well worth putting some time in to fix any small problems.  Heck, you got over a $1000 worth of weights!

 Wish I could help with the problem, but no experience.

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When the whistling is occurring, everything works, including the steering.  When I dead head a remote, you can hear the pump whine.  Both remotes up and down make the pump whine.  I do not have anything at the moment to connect to the remotes.  My father in-law has a disc plow that's the perfect size for this tractor but I'm not going to hook up to it until I change the hoses and cylinder.  It's been 2 decades since it was used.

Also, yes while the whistling is going on, I can feel a vibration in the steel hoses on the MCV.  I DID NOT change the o-ring when I changed the filter😣 but will order a new one.  I'll order new seals and bleeder screws for the fuel filter housing as they are beat up as well and I have a slight leak up there some where.

When I picked it up, I put the white Diesel Clean tank cleaner in the tank and let it slosh around on the trip home.  I have been adding the grey Diesel Clean every time I put diesel in.  3oz per 5 gallon.  The guy at the bone yard where I picked up the ROPS told me to make sure I do that or I'll spend more on the pump than the tractor.

I have a repair manual but not the owners manual and I leave the 3pt down to make sure it doesn't go anywhere even though it's parked on flat ground plus I have 2 small kids I don't want them to get under it or run into a raised implement.

54 minutes ago, J-Mech said:

Congratulations on your steal!  You got a good deal, and I think the tractor looks to be in good shape.  The non matching tires would drive me nuts!  OCD I guess.

Thanks, it bothered me a little at first but I have a friend who farms for a living and he told me as long as they hold air don't worry about changing them as I'm not needing it to pay bills.

13 minutes ago, Jeff-C-IL said:

I agree, that is an real nice find and well worth putting some time in to fix any small problems.   Wish I could help with the problem, but no experience.

Thanks, I wish I could find a few more in the same condition and price.  I'm pretty proud of how good she runs for the money I spent.  

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Jason, below is link to 74 series downloadable manuals for the European models.
The European models are slightly different in electrical and some options and the 84 series is just an improved 74 series so the 674 and engine manuals are good for you.

Yes the Diesel fuel additive is good.
Vibration on the steel lines usually indicates air in the hydraulic oil. In the Service Manual in section 10 there is a hydraulic test/trouble shooting section.
Re Dead heading the remotes, you should hear it load the engine and the relief valve in the MCV do a squeal or buzzing noise, don't do it high RPM as it could burst one of the rear remote hoses. 

link: https://www.redpowermagazine.com/forums/topic/121219-d239-674-engine-manual-pdf/

 

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Thanks for the links to the manuals.  I will try to download them this weekend.

I did check the remotes yesterday.  The engine loads and you can hear the valve in the MCV make the normal noise you would expect from a hydraulic valve.

I'm going to order a filter and o-ring and start there.

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Welcome to the forum Jason, it looks like you really got yourself a deal!  The tractor is very much worth fixing up , I guarantee If I saw it on a dealers lot here in Pa. just as pictured I would expect a price of $4500 to $6500. I have a 684 and it is a really great tractor. Hopefully Changing the Hydraulic fluid and filter will take care of the whistling noise. When you remove the filter about a quart or two of fluid will come out of the housing. Check that fluid and the filter for foreign debris which can be pieces of brake lining from the parking brake. The parking brake problem is probably the most common issue on these tractors and the bits of brake lining get into the transmission case and thus mix in with the hydraulic fluid.

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This weekend I pulled the filter just to see what was inside while I'm waiting on new o-ring and filter.  There were no particles that I could see in the filter or on the by-pass screen.  I also pulled the flow divider spool and pressure relief valve on the bottom of the MCV.  Both moved freely, were clean, and there was nothing on the screen on the relief valve.  I didn't take the valve apart.  When I drain the fluid I plan on pulling the PTO clutch cover and taking a peak inside.  The whistling noise is definitely coming from the MCV.  You can really tell when you pull the parking brake cover and put your head next to the parking brake handle.

Also, I should mention the left brake is spongy only at idle.  When the rpms are up (1500-2500) the pedal is firm.

I'm going to borrow a gauge to check pump pressure at the remotes just to rule that out.

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  • 2 weeks later...

Changed filter o-rings, lines still vibrating.   I went ahead and drained the fluid and pulled the PTO cover.  Other than all the cases look like they have been painted with a tan paint, there is no sludge or major items I can see in the case.   I got 5 gallons out of the middle drain plug, about 3-4 out of the rear and not even a gallon out of the front.  Just from a couple minutes of idling,  there was a bunch of air bubbles in the fluid.  Any ideas what else to look for before I put fluid back in?  Dip stick has been showing above max.

Also, the banding material looks like it is on the parking brake.  I might just need to adjust it to make it work.

What is the black plug at the bottom right side of the case under the PTO cover?

Edit to add: the remotes were getting 2600 psi at idle.  Either cold or while the whistling was happening.   When whistling, it built a little slower but I guess that's due to the air in the fluid.

Thanks, 

Jason

I replaced the fuel pump front cover and the fuel line from the filter to the pump.  Should take care of a couple of leaks.

 

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After thinking about this last night, I'm guessing there was a fair amount of water in the hydraulic fluid when I picked it up.  Dirt and water is what has covered the casted casings with the brown color that will show up on a rag but not come out of the pores of the castings.  As it gets warm, the water starts to evaporate and carries the dirt particles with it to the breather causing it to clog and turn brown.   Also, this is adding air to the fluid and possibly steam.  So the whistling is like a tea kettle letting off steam.  

That is my theory.  Other than keeping the fluid clean and possibly a few frequent changes, what else can I look at?  I'm guessing more has to be removed to find the transfer pump or screen.

A clarification of my first post.  When warm and sounding like a tea kettle, the 3pt won't or is slow to lift the shredder (JD709) at idle.  Not that the 3pt won't lift at all.

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The transfer pump is hidden by the PTO clutch, if you have a dental mirror or bore scope or a fibre optic camera for your smart phone to look on far side of PTO clutch on the bottom is the inlet for transfer pump. There is a test for transfer pump, leave tractor sit over night, check trans/diff oil level with dipstick, remember the mark, start engine and let run at 1500 RPM for 5 minutes and check dipstick again, the level should have gone up or down, I can't recall which. You are always supposed to check trans/diff oil level after tractor has been running for 5 minutes as the transfer pump is supposed to equalize the oil levels between the different compartments in the trans/diff.
There is also an access panel under the seat but I can't remember how much you can see other than 3 pt stuff.

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