D6T that blade lower has been becoming slower and slower?

[Per Eriksson]

Need some ideas as to what is going on with this machine, its a D6T prefix #LKJ
Blade lower has become slower and slower the last year and now it wont even go into quick drop mode.

Checked pilotpressure from the joystick on the raiseport and that is a solid 3000kpa but on lower it only manages to come to about 1400kpa.

So we switched the pilotlines around between raise and lower on the main valve but it still shows us 3000kpa on raise and about 1400kpa on lower, What the heck?

Pull the liftspool and expect to see some scoring that cause the pilotpressure to bleed away to the return channel inside valvebody but cant see a damn on the spool, hard to see inside the valve but can't feel anything odd.

Is someone pulling my leg or could the valvebody be so worn that the pilotpressure bleeds off into the body?

Anyone encounter this before?

 

[JDOFMEMI]

I have a similar issue on a D-6T LGP, sn KJL00542. I have not done anything about it yet, but will be curious.as to how what you find.

Mine is not too slow yet, but it will not quick drop, and will not lower fast enough to compensate when grading rough ground. It also does not float.

 

[d9gdon]

Same thing here D6T XL, sn LAY11XX. Took the quick drop valves apart and tried to recalibrate hydraulics twice to no avail. It was a lease dozer, never did figure it out and got a replacement tractor. It was impossible to grade with. I want to say that float wouldn't work on it either, can't remember for sure.

I'll be anxious to see what you can find.

 

[Construct'O]

You might want to check the accumulator next to the high pressure manifold.They get low on nitrogen and slows the blade and quick drop will not work.You could try to recharge it or just replace the accumlator something like in the $250 range.Then recharge it with nitrogen.That has been fixing them here.Good luck

 

[Per Eriksson]

I think you are spot on, checked it and it didn't have any charge left whatsoever, new one is coming in tomorrow.

 

[JDOFMEMI]

What does the accumulator do? The older machines functioned fine without having them, so what is the need for one on the newer dozers?

 

[Nige]

The implement pump can't supply enough flow at full cylinder speed. It's the same function as accumulators on the steering on an off-highway truck. Basically you can build a machine with a pump half the size as the old ones were.

 

[JDOFMEMI]

Nige

Thanks. That makes sense.

Now, does it only work on the lower circuit? The lift seems fast enough, only the lowering is slow.

 

[Nige]

Without going into the SysOp I would hazard a guess that the blade goes down faster than it goes up because of the weight of the blade (all considerations of the quick drop valve aside that is)..............

 

[DPete]

The quick drop doesn't work correctly on my R either, like it's not getting enough pilot pressure to open the valves. It will drop at high idle but not slower. The normal down is ok as is up. Had the quick drop valves apart, all looked good, put new resolvers in the control valve, helped some but it's still not right.

 

[Per Eriksson]

Changed it and it works as a charm now.

Basically it ensures there's always enough pilotpressure avaliable even in situations where the pump is at standby like when dropping the blade.

A quick test for the folks that is having lowering issues could be to run another function a little in a stall so the pump builds a little presure and then try blade drop if it works as it should.
There's also an updated sleeve for the quick drop valve that might help.