JD 2850 Loss of Hydraulics

[britcivic]

After being really impressed with my 1140 4wd I finally managed to get my hands on a 2850, bit of a fixer uppa, but it really wasn't expensive (probably will be by the time I've sorted this problem)

When I got it I checked the hi lo dropping out at low revs when you pull the stopper out, and that was fine, and still is.

But today I've found some strange problem that I've not come across on the forums yet.
After a long run on the road (1hr) the brake pedal went solid, like it was mechanically locked, after I stamped on it to stop I lost all hydraulics, no steering brakes, or lift arms. I gave it a bit of rev and after a few minutes it came to, and worked for the rest of the day (with an Atlas crane on the 3 point running off the spool) and an hour trip back home with no issues.

The locked brake pedal did happen the day before, but no loss of hydraulics that time.

Anyone have any idea what could be going on?

Bit unnerving thinking the brakes and steering could go any minute...

 

[Tractortech]

Now Then..
Brake pedal went solid?? Which cab do you have,,, MC1, CC2 or SG2??
How is your crane piped, & is the valve set up for closed centre hydraulics??

 

[britcivic]

Yes brake pedal went rock solid right at the top of travel. It's SG2 cab with the sideways move of the lever for hi lo. The crane has a Parker HV07 spool block with closed centre plug fitted and 1/2" return pipe direct to the transmission plug hole. Hydraulics are still really strong on the crane, better than the 1140 was even after the 'blip' this morning.
The only thing I could see out of the ordinary was that the handbrake shaft had come out of the transmission casing by about an inch sideways towards the left rear wheel. This has worked it's way back in now - I couldn't push it back in by hand when it was sticking out. -could that be related to brakes jamming?

The transmission oil warning light now comes on at idle too, although the power steering and lift arms still work ok.

The lift arms do fall slowly immediately that you stop the engine- that was the only obvious thing wrong with it when I bought it.

 

[roscoe erf]

at a guess id say you've got debris in the system either from the brakes or the front orbital pump starting to brake up when mine went in my 2850 it effected the steering on odd occasions and it slowly got worse until I lost lift arms and brakes and steering expensive job all the bits get dragged through the whole system

 

[britcivic]

I was starting to think along those lines - could it be a disintegrated synchro?
It WAS the only tractor I've had that didn't crunch into any of the gears, until a friend took a test drive in it and now 3rd gear synchro has disappeared completely..... Shouldn't be brakes as they're (allegedly) new as is clutch and hi lo pack...

 

[britcivic]

I have replaced both hydraulic filters and cleaned the trnsmission screen filter, which had a few small flakes of steel in it, but nothing that looked catastrophic. Tractor seems to be working fine.

I'm now trying to work out how I could have had an intermittent total loss of hydraulic pressure?

would that happen if the transmission filter bypass valve stuck open with debris in it?

-thinking of pulling that next -should have done that before I refilled the oil!

 

[Tractortech]

I've seen one of the roll pins in the filter bypass valve break occasionally but that's not intermittent.
Has the hydraulic pump been out?? I've seen people put it back in, dislodge the key on the shaft so it's only driving on the shaft tightness.
The bypass valve is above the filter so you'll not loose any oil. Take care putting it back, it only goes one way. I assume you have the correct transmission oil filter AR75603 installed and the plate and spring are correctly located below it??
I've just read previous posts..
The handbrake shaft if correctly installed may possibly have some endfloat but will have no effect on the service brakes as they are completely independent of one another.
Is the tick over set correctly at 800 rpm??
Does the light come on with the Hi Lo in High, low or both?? What oil are you using in the transmission??
If your crane is closed centre with the relief valve is set to 190 bar or more and no single acting rams, I'd put the return into the transmission oil filter bowl..

 

[britcivic]

Thanks for that- I've just put genuine Hyguard and genuine transmission filter in, return filter is fleetguard. When I took out the old transmission filter the circlip had ridden up the shaft so the plate at the bottom was loose - I presumed this happenend when I unscrewed it - could that have been the cause if it was already loose? I've put it back properly now anyway. Tickover is correct, the transmission oil light doesn't come on now.

I think I'll phone Nick young after a bowl with the fitting in the side to plumb the return back to, or pinch the one off my 1140 as I also have a hydraulic winch to fit to the front weight block which worked fine on the 1140 with it plumbed that way.

 

[britcivic]

I dismantled the pump drive today and all was well, and pulled and cleaned the bypass valve, again all appeared ok. The one off loss of hydraulics still has me stumped, also the solid brake pedal, which usually feels like it needs bleeding, so not solid at all really...

 

[haybob]

I had a 2650 that used to lock up hydraulics on tick over after it had been working hard.I never looked into it though she's gone now. Wish I still had it some days.

 

[britcivic]

How do you mean lock up hydraulics? As in solid brake pedal like mine? Must have been a good machine otherwise if you still wish you had it! I'm definitely fixing this one- everything about it is perfect for what I want, although I have to say I think the MC1 cab is better for access and visibility, although I might just not have got used to the SG2 yet......and on the plus side, if it rusts any more I'll be able to see out through the holes....

 

[haybob]

If I let the revs drop down to 1000 rpm (just after a good run on road) then the arms and steering would freeze. Just had to rev it back up past 1800 for a few seconds and everything would come back to life. I'm not sure about brake as I was never in a position to need it when It was parked ticking over. it was just one of those daft things it seemed to do . It was fine again after and would happily potter around yard without a lot of revs . Drove a older 2140 which did similar thing. Your sg2 cab is the best cab . They where a comfortable cab to sit in all day.

 

[britcivic]

Sounds similar- I'm working half an hour away tomorrow, so will see if the symptoms come back at that range...

 

[Tractortech]

The brakes should never go solid, they are the simplest set up ever. The pedals never seize on the pivot like was possible with OPU, LP, MC1, CC2 etc..
Unless,,,,,,, the pedals are incorrectly adjusted and trapping the oil in the brake lines/pistons. Then with heat, the trapped oil expands,, but that would cause noticeable drag and power loss.. Earlier 40 series tractors couldn't get the steering return oil back to the transmission fast enough. If you steered too quickly, the brake lights would come on...

 

[britcivic]

That second bit sounds like what may be happening - I'll have to read the manual on brake set up.
I presume they may not be returning to the right place to release the oil? I have briefly tried to bleed them with no improvement, they still need one press to pump them up to the top after starting.
The tractor does pull like a train, so not sure I'd notice the drag with it running full tilt?

(BTW got 2 miles down the road today before one of the rubber unions in a return line split - lost most of my nice new oil, had to put the old stuff back in - it never rains but it pours!)

 

[britcivic]

Just thought: Could the trailer brake trap oil in a similar way?

 

[celtis man]

nobody has mentioned the dreded internal hydraulic pump which can cause loss of hydraulic power but never heard of locked up brakes before

 

[Tractortech]

That second bit sounds like what may be happening - I'll have to read the manual on brake set up.
I presume they may not be returning to the right place to release the oil? I have briefly tried to bleed them with no improvement, they still need one press to pump them up to the top after starting.
The tractor does pull like a train, so not sure I'd notice the drag with it running full tilt?

(BTW got 2 miles down the road today before one of the rubber unions in a return line split - lost most of my nice new oil, had to put the old stuff back in - it never rains but it pours!)

You'll have more travel on the 2850 brake pedals than the 1140 due to the retractors fitted to the 50 series tractors. The trailer brake valve will add a bit too, your 1140 may not have trailer brakes?? Later tractors had a revised master cylinder but only to try to improve the feel of the brakes..
I can't see the trailer brake valve causing the solid pedal thing. It has a separate little piston to move the valve spool and is sealed with an O ring.

 

[J428TGS]

if I remember right the hi-low is on the low pressure pump in the rear end, that has a pick up pipe that splits due to age that causes the lever to fall out.

 

[Rust]

Does the cab have to be removed to access transmission pump ?