D7G blade goes down slow when oil is warm

[Bullcat]

My D7G is having an issue where the blade goes down slow when the oil is warmed up, the blade works fine when the oil is cold. Also float will not work at that time and the pump is noisy when it is having this problem. Linkages are all fine and I replaced the oil filter. Its very frustrating to run this way and I have not been able to find the cause of this issue any help would be much appreciated.

 

[hetkind]

How old is the hydrolaulic fluid? Sounds like captivating on the pump...

 

[Heavey Metal]

If the blade tries to tilt when going down vs up than you prolly have a bent rod or barrel

If it stays even than I would suspect the quick drop valve.

 

[Bullcat]

The tilt works fine or normal when the problem occurs and has no effect on blade control or vise versa. The pump noise does sound like cavitation. I've never been into a quick drop, what does it consist of and what could be wrong or damaged. If I had a damage or bent cylinder I would imagine the problem would be constant not just when the oil was warmed up after several hours of working normal.

 

[Delmer]

Does the pump only make the noise when you try to blade down? or all the time when the oil is hot? And the blade lifts fine when the oil's hot and it's slow to lower?

 

[Heavey Metal]

Debris from the cylinder etc.

Tear it apart and learn

It is dead simple (quick drop valve)

Once again check the rods and the barrels for damage.

 

[Bullcat]

When the problem occurs the blade lifts OK but that's when the pump is noisy, then is slow to lower and is slow in float and no noise from pump when lowering. It was run for 8hrs today and no issues today, it worked as it should. I have not changed anything since it ran last Friday when the issue last occurred so I'm scratching my head where to look for the problem but I'm wondering about the quick drop.

 

[Delmer]

I was just curious. Heavy Metal seems pretty sure of the quick drop valve, sounds like good advice to me.

 

[grandpa]

When you changed the filter, did you cut it open for inspection?

 

[jeffrob]

The noisy pump indicates cavitation, which in turn is caused by a lack of oil flow to the pump, and/or sucking air. Could it be that their is a rag or something similar floating around in the hydraulic tank or some other blockage in the hose or filter on the supply side of the pump?

 

[Bullcat]

I have not had a chance to cut open filter yet. It was working fine for 2 days and then today the the problem showed up again. Not sure if its coincidence but the days that it worked fine it was working on fairly level ground and the days the problem has showed up was when working up and down steeper grades. When its warmed up there is a lot of air pressure in the tank when I open the fill cap, also there is some foam on the surface of the oil. Its alot of pressure for heat expansion and I'm not sure what is causing the foam on the surface of the oil. Maybe that's normal but I haven't seen that on any of my other equipment.

 

[Nige]

Foam would indicate to me that air is getting into the system on the suction side possibly causing cavitation. The pressure in the tank is normal, when the oil gets hot the pressure in the air above it helps to push the oil into the suction side of the pump. Ideally you should never open the tank cap unless the oil is cold.

 

[Bullcat]

Thanks for everyones input, I will check for any possible air leaks on suction side first as that sounds like a real possibility cause of the cavitating pump noise and foam in reservoir. If no luck there then I'll check the quick drop.

 

[Bullcat]

I removed floor plate to inspect suction line to the pump and decided I didn't have enough time today to dig into that spaghetti nest of hoses with the large suction line at bottom of it all. So I did take apart the quick drops, yep dead simple and in my opinion nearly bullet proof. Nothing wrong there that I could find. While inspecting the suction line and pump I noticed that they were what I call dry oily dust covered, not wet, indicating that there must be a really light seepage of oil. Im on board with the possibility that the pump is sucking air, If it was sucking air into the system would the the cylinders be spongy like when you have air in an empty system that was just filled? This problem shows no sign of sponginess. Blade goes up normal with noisy pump and goes down real slow with float being slower and no noise from pump, down pressure is good and I can fine grade OK with it.