Hydraulic system troubleshooting help, I'm stuck

[STx]

OK, so here's the full story. I have a New Holland TC40-DA. About 9 months ago, I had a fitting get damaged on the suction line and my pump was starved of fluid a few times. I replaced the fitting, changed the fluid and started having problems with aeration in the fluid. The pump was getting really hot so, with a 2nd opinion, I figured the pump was probably damaged and needed to be replaced. This weekend, my hydraulics died completely (except for the HST and power steering which have their own pumps and have been working normally the entire time) so I bit the bullet and ordered a pump. It got here today and I've installed it. I'm pretty sure the old pump was definitely a part of the problem as I'm able to turn it easily by hand and I had some metal shavings in the screen on the high pressure line into the manifold but, it hasn't completely solved my problem.

It does appear that the aeration issue has been solved though, I ran the tractor for about 20 minutes after replacing the pump at 2700 RPM and while it started very aerated (to be expected since the suction side line had to be removed and was dry when I started it up), by the time I shut it off, the fluid was clean with no air bubbles in it.

The problem that I'm still having though, and it's now worse than before it just stopped, is that the hydraulics for the 3 point lift and the FEL are VERY slow and jerky. They'll move jerkily for about a second and then pause for 3 - 5 seconds and then move jerkily again. Once things are up, I can shut the tractor off and they stay there (they've been in the same lifted position for about an hour), so I don't think I have cylinder problems.

I'm thinking at this point that my issue is probably in the manifold or the relief valve but I want to be sure before chasing that down because the factory service manual, and the parts catalog, say that those are not serviceable parts and need to be replaced. If I was going to do it, I'd probably replace them both since the manifold comes with the relief valve. It's an $800 part (the relief valve alone is $350) so, like I said, I want to be sure before I spend the money. The parts are too expensive to just swap out and see what happens. I guess I could pull them off, clean them and check for any scoring, wear or debris plugging them up/

I have the factory service manual and it gives the procedures for testing this stuff but, they involve a flow meter and pressure gauge, neither of which I have. So I'm kind of stuck, not really sure what to do next.

Anybody have any suggestions?

 

[STx]

I pulled the relief valve this morning. There were no shims in it, which seemed odd since the manual calls for them but, I don't otherwise see any obvious issues with it. Since the shims only add 150PSI each, I can't imagine that the lack of them is the root cause of this.

I'm working on removing the whole divertor valve but am having some trouble getting the PTO line off of it. Decided to take a break before I started throwing things.

 

[STx]

Got the divertor valve out, it looks OK to me also. I guess I'm just going to replace all the O-Rings, the filters and the fluid (again, this fluid was changed 15 hours ago) and see if that helps. I don't know what else to try/check. I guess if that doesn't do it, it's going to have to go to a shop.

 

[oldnslo]

What does the diverter valve do on your machine? To me "diverter" indicates it directs fluid to multiple points. If this valve is attempting to divert or dirct oil to various functions and is sticking or binding it could cause the symptoms you are describing. If the spool and or bore have nicks or scratches on them be very careful when polishing them to prevent rounding of the metering edges / "lands". This can adversely effect the valve operation.

 

[STx]

It decides whether the valve block sends fluid only to the 3 Pt or to additional hydraulics, like and FEL. Here's the manual page which describes it better than me.

 

[oldnslo]

If this is not a sliding valve I doubt it is your problem. I was refering to a spool that slides in a bore against a spring load.

 

[STx]

The only thing I can think might be an issue with it is that it could be leaking fluid past the o-rings to the bypass and causing me to lose my pressure. Maybe the same problem with the relief valve, I'm going to replace them all and see what happens.