JD TLS Problem

[Lofty]

The TLS on our 6420 creeps up while the tractor is parked. Over night it raises nearly right to the top of its travel. As soon as you start the engine, it drops to its working height and works fine. No warning light but it does buzz on and off for a few seconds on start up.
Dealer suggested swapping the solinoid valves in the spool block above the axle around to see if it went down which would suggest a faulty valve which I've done but it still goes up.
Any ideas?

 

[NZ Tech]

How hard does it ride.. And how many hours has it done?.

 

[nick...]

My6620 has a mind of its own with the tls.sometimes when tractor is turned of it will raise the front extending the tls ram.stopped it earlier today and it settled nearly to the stops then raised up a bit.allways sets itself on start up and been no trouble for years.
Nick...

 

[NZ Tech]

From the top of my head.. The accumulators are pushing oil to the extend side of the rams when keys off. So bypassing thru the tls valve somewhere. I have a look at schematic tomorrow. Ive also seen this happen but not one seems fussed to fix it .

 

[Lofty]

How hard does it ride.. And how many hours has it done?.

The ride is quite hard compared to others we have. I changed all three accumulators a month or so before it started raising itself but it didn't seem to improve the ride much. 5000hrs on the clock.
I'd like it right as in all other respects the tractor is pretty A1.

 

[NZ Tech]

You say you've changed the accumulators... What were they gassed to pressure wise. This sounds silly but i've seen them replaced and no gas added to them. With what you are saying it sounds like they might not be gassed up. Funnier things have happened!!!.

Edit: I would say one of the accumulator sets has gas in them. There is one big(on raise side) and two small(lower side) they will all have to be retested. Makes sense that the one without gas is allowing the suspension to raise up as the ones with gas overcome the weight and fill the rams slowly. This is where I'd start.

 

[Lofty]

Ummm. I was recommended new accumulators under the assumption that if the old ones have leaked, they will leak again and the new ones would be gassed and ready to go. All three new accumulators came over my JD dealers parts counter, out of JD boxes and matched exactly what I took off. Two are rated at 40 bar and one at 48 bar. All three are the same size.
Are you suggesting I've paid good money for something no better than what I took off?

 

[NZ Tech]

They dont usually come with gas in them you see as air freight they would explode. So you buy, get them gassed to spec and fit them.

There should be two the same size with 580psi nitrogen in them and one larger one with 696psi.

The accumulators should not all be the same size. Repeat one large one and two smaller.

 

[Tractortech]

Now Then..
We in the UK have nitrogen accumulators delivered (with gas) by road from EPDC. Things must be different in your part of the world NZT...

 

[NZ Tech]

Then the best thing to do is start with checking the pressure in the 3 accumulators and then from there.

Things are definitely different here. They ship them.

I doubt if the TLS valve would have the much to do with this raising issue over night. Maybe a better way would be to remove the big accumulator and plug the line up and calibrate the suspension, then leave the machine over night and check the heights again in the morning. Oh and recheck the bleed valve is closed on the TLS valve- the bleed screws are marked "N". Tighten them down gently .

 

[Lofty]

Now Then..
We in the UK have nitrogen accumulators delivered (with gas) by road from EPDC. Things must be different in your part of the world NZT...

Thanks for giving me a little bit of confidence in what the dealer told me.

 

[Lofty]

Then the best thing to do is start with checking the pressure in the 3 accumulators and then from there.

Things are definitely different here. They ship them.

I doubt if the TLS valve would have the much to do with this raising issue over night. Maybe a better way would be to remove the big accumulator and plug the line up and calibrate the suspension, then leave the machine over night and check the heights again in the morning. Oh and recheck the bleed valve is closed on the TLS valve- the bleed screws are marked "N". Tighten them down gently .

Just organising getting the pressures checked. The tractor needs a calibration of the clutch pack and hitch so they can add the TLS to the list.
Thanks for your help.

 

[SteveO]

I have noticed that my old 6920P went up over night if the front weight was not on it and went down when weight was on it. But it worked great. I was thinking that the pressure in the accumulator was too low and the membrane would stretch and it went down. 6930P with 900kg weight stands where you leave it.

Can those accumulators be repaired/overhauled ? I have heard that they cost like 500 GBP a piece ?

 

[Lofty]

Can those accumulators be repaired/overhauled ? I have heard that they cost like 500 GBP a piece ?

They can be re-gased but the theory is that if they have lost the gas, the diaphragm is damaged and will loose the new gas.

If you talk to your dealer nicely and get him to lean on the discount button when he books them out, their about £250 each. My problem is that I've not seen an improvement by spending the money.

 

[Timbo]

@Lofty Have you recalibrated the TLS after the new accumulators?

 

[Lofty]

No, not yet, it's on 'to do' list.

 

[NZ Tech]

You just regas them annually- set a hour schedule to check them as no point buying a tractor with suspension if it doesnt work 100%. If the gas is low they can be topped up. If the accumulators are empty I probably wouldn't bother gassing them as the bladder will be damaged. Within reason with all of this as if the accum's are 10yrs old there probably is no reason to try regassing just replace.

I have noticed that my old 6920P went up over night if the front weight was not on it and went down when weight was on it. But it worked great. I was thinking that the pressure in the accumulator was too low and the membrane would stretch and it went down. 6930P with 900kg weight stands where you leave it.

Can those accumulators be repaired/overhauled ? I have heard that they cost like 500 GBP a piece ?

 

[SteveO]

These on 30 are good but those on 6920 that I have sold to a friend still goes ok and when it was mine it went up or down till tommorow. I was wondering if those bladders can be repaired/exchanged since I got that info about 500 pounds a piece, I hope I wont need that.

 

[NZ Tech]

The sfa position sensor would be failing with that description.

Accumulators dont set the height they are for cushion only.

 

[SteveO]

Well it goes up without weight after power down, so in 2 days while standing in the garage it goes up or down, dont think thath sensor works then. When working it works ok. I got one time some error for that sensor in the field and then TLS goes limp, it goes then like it is on springs, freely.