D200 Hydro Pressure issue

[pfrederi 17,634]

OK I am feeling a bit stupid today and want to check my logic. Just put a Hydro pump and motor both that I overhauled in my D200. She moves great!! However the 3 point and mid mount barely work. Put the pressure gage on the pump and I broke it. (was only a 300 psi gage as I was just going to check the charge pump pressure which should be 75-150 lbs) Gage pegged. Put the 1000 psi gauge on and it showed 800psi. Moving the 3 point and midmount control did nothing to change gage nor did they move much.

I am thinking that something is wrong with the charge pump relief valve...but if the charge pump is generating 800 psi why do the 3 pt and mid mount not move well? My understanding is the charge pump relief valve should open at 75-150 lbs and then vent the fluid through the implement lift valve. Which if no implement is in use sends it back to the pump reservoir.

Is my problem in the charge valve relief or in the implement lift valve body it self???

Paul f

[wheeledhorseman 574]

A couple of quick thoughts Paul.

You seem to be right with your thinking and either could be possible reasons.

My understanding matches yours...

The charge relief valve should open and alow fluid to bleed past it so that the charge pressure is kept in the range 75 -150.

If the valve were to get stuck shut or perhaps barely able to open then yes the charge pressure will soar as the bleed off isn't happening / hardly happening. In this case there's next to nothing available to flow through the implement circuit so it will barely work.

The 800 psi you read is on the pump side of the valve but with the valve pretty much stuck shut there's next to no bleed past it to operate the implement circuit. So my first suspect would be as you say the relief valve.

Yes it would also be possible for a 'blockage' in the implement cicuit to cause the same result i.e. the charge relief valve tries to open but there's nowhere for the bleed past to go. As a result the pressure soars but there's no flow through the implement circuit so it won't work. I would think this is the less likely though.

Andy

[JamesBe1 82]

Hmmmmm. According to the manual, the implement pressure should be 550 to 700 PSI. I guess 800 is ballpark high.

The charge pressure is 70-150PSI. Are you sure you measured the correct location? It sounds like you measured the implement pressure. But, the manual says to use the "same gage hookup as the charge pressure test" to do the implement pressure test. WTF does that mean?

Reviewing the diagram, I see that some have an optional implement relief valve. What would be the effect if that were stuck open of closed?

Very curious. I hope some of the other dysfunctionals chime in. I'm scratching my head over this one.

[pfrederi 17,634]

Andy and James: Thanks for the feed back.

James, this is the pump that you and I looked at last year. It has both charge and implement relief valves. Interesting that the charge valve is on the the push valve side of the pump when there is an implement valve but on the other side of the pump if there isn't an implement valve

Andy, since the implement control valve worked (except that I couldn't use the mid mount as the valve control handle has been broken for the last several months) up until last week when i started the tear down, I am assuming I did something wrong during the hydro pump overhaul in the charge pump relief valve...Too many shims or a wrong spring. This afternoon I will pull the valve out and see what is what. I have 2 other pumps I can pull their relief valves for comparison.

Thank you both for your thoughts.

[pfrederi 17,634]

Well now I feel even dumber. Took the charge relief valve out and found it had the heavy spring as used on the implement relief valve. Now I am telling myself that the pump I worked on must have come that way...I could never do anything that stupid.

Anyway put in a lighter spring and retested... Charge pump was about 110 lbs went to 400 while the lifts operated then went to almost 700 when the lifts hit full travel.

Was going to take her out for test drive but it started snowing.

Anyway thank you Andy and James!!

[JamesBe1 82]

Awesome!

Did you have to remove the pump from the tractor? I almost cringe at the thought of it.

[tommyg 152]

You brought back some memories of my high pressure problem. Except mine was a stuck implement valve. Glad you had a happy ending!

[wheeledhorseman 574]

We often forget to factor into our thoughts on these things what a PO may have done. In this case my guess would be that it was done in an attempt to raise the charge pressure in a hydro that was basically very warn.

Good to know that the readings are now good.

Andy

[coldone 35]

Glad you got it figured out.

[pfrederi 17,634]

Awesome!

Did you have to remove the pump from the tractor? I almost cringe at the thought of it.

No all you have to do is remove the body side panel and you get a clear shot at at charge pump valve... about the only easy part of the project.

The more options on your D series the harder it is to work on.

To replace pump and hydro motor it is best to strip off the FEL and frame, the rear PTO shaft and bearings, the left side turning brakes, both rear wheels and the steering column. Then remove what the manual tells you to. :)

Edited February 1, 2013 by pfrederi