1995 Lull 644TT

[Douglashd16b]

Good Afternoon everyone, I bought a1995 Lull 644 last year to use on the farm and it has a hydraulic issue I cannot seem to figure it out, I know alot good mechanics are on here. My problem is one of my stages on the dual pump is constantly loading the pump up and if I use it for any period of time the oil will heat up so bad that you can't touch the tank.when it does this I have no pilot pressure so the machine is dead until It cools off. This is a control manifold hydraulic machine. Any help is greatly appreciated

 

[Vetech63]

Some pics of your pump and control valve system would help.

 

[tractormech]

Whats the model and serial number. You have a somethong bypassing causin the oil to heat up

 

[Douglashd16b]

 

[Douglashd16b]

1995 644TT-34

 

[Douglashd16b]

 

[Douglashd16b]

This is where the hissing is coming from and I can feel it getting hot there

 

[Vetech63]

View attachment 350195

That looks similar to a thermal bypass valve but I can't see where the lines are running.

 

[tractormech]

Is that the foot brake valve?

 

[Douglashd16b]

That is the pump unloader valve, I just took it all apart and all seems fine

 

[Douglashd16b]

I'm sorry,I was wrong, this is the Accumulator charge valve. I need one,anyone know where I can get one. PN. P28728. Thanks in Advance

 

[B&B]

I'm sorry,I was wrong, this is the Accumulator charge valve. I need one,anyone know where I can get one. PN. P28728. Thanks in Advance

Web equipment out of virginia should be able to help. I was recharging an accumulator on a lull and had questions on the pressures and they were more than happy to walk me through how they do it and gave me any info I could need.

 

[Douglashd16b]

Already tried Web, they don't have one

 

[Douglashd16b]

Guys, I found a used valve by chance, put it on and have the same problem. Boy I thought I had it. I have a question for those that are familiar with these machines, Am I suppose to have pressure with the engine running and no functions activated. I ask because one section of the the dual pump only has pressure when I turn the steering wheel, the other section which is the one that I am having problems with will build to 1900 psi and kick out then immediately load up and start again and yes I have 450 accumulator charge. Any help would be much appreciated

 

[Douglashd16b]

 

[Douglashd16b]

Update, I changed this valve [ called brake port block] and it fixed my problem