Hydro Gear EZT 2200 Rebuild

nccole

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I am in the middle of rebuilding a Hydro Gear EZT 2200. Left side, out of a Husqvarna RZ5424. It started going out around 90 hours, but was out of the 3 year warranty by a couple of months. I mow 2 flat acres and knowing what I know now would have bought something with a 2800. The Husqvarna tractor itself is a very nice well built unit, and I opted for the Kawasaki engine. I bought a new one (so it was claimed) and it isn't perfect, but I can get the job done. It overheats after about 10 minutes and I suspect the fluid is contaminated. I read that these are sealed maintenance free, but found a rebuild manual from Hydro Gear. I printed it out, and bought a seals kit and internal filter for it ~$40. I figured if it is shot and if I do nothing with it and at worst I threw away $40, but could save a lot of money, plus it might be fun. I am hoping to find some people who have had these apart at least and who have re-built them possibly.

So far, I think I made a good decision, the gears, shafts, and all critical components look great. The oil doesn't look too bad. The one problem, and a good one I think, is the filter. It seemed to be full of aluminum dust. What I think and hope is that the "center section" that the filter bolts to was just poorly cast and/or poorly machined. It looks rough, and I suspect that in my first 90 hours, the oil moving through the pump has collected and transplanted enough aluminum dust into the filter that now the transmission of power is not possible. I don't have it exactly in my head how this thing works yet, so who knows. Once I started noticing issues with it, it was only about 10 hours later and it now has no power. This is not the issue with good power when its cold either.

So, does this sound reasonable to anyone in the know? What else should I really look at while I have it apart? I don't see any scoring or broken/chipped gears in there, but I haven't cleaned it all up yet either. I haven't read these forum rules yet, but do have pictures I could post if that is possible and would help any.
 

ILENGINE

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I am a hydrogear authorized service center so I have been inside of that unit. If the center section or the pump or motor surfaces where the unit run against each other have scratches deep enough to catch a fingernail, that part will need to be replaced.
 

nccole

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I am a hydrogear authorized service center so I have been inside of that unit. If the center section or the pump or motor surfaces where the unit run against each other have scratches deep enough to catch a fingernail, that part will need to be replaced.

Thank you for the quick reply. I will check out that center section more closely, and I thought replacing it might be a good idea anyway. I haven't found a real p/n for it yet as the manual has a generic parts list 1-159.

Is this common to have what I figure is just a Chinese poor surface finish part that is causing this "failure?" Is this unit worth while to rebuild? Everyone says NO, run away and buy a new one! But for $40 and some labor (free in my case) I can save myself around $800. How does that not make sense especially on a good tractor with 110 hours? This job really isn't that bad, working on my cars is almost always a bigger pain and more frustrating. Also, you know why the left unit is usually the bad one? Sorry for so many questions, just seems these are a mystery but I don't know why, and you are the first person who actually knows more than me about them.
 

ILENGINE

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The surfaces on the pump, motor, and center section that mate together are glass smooth polished on new units, So if you can catch a fingernail in grooves between the holes, it is damaged and needs to be replaced. I actually live 60 miles from the factory in Illinois, and just went through a factory tour and tear down school back in January.

The outer surface of the center section is rough because it still has the dimples from the lost foam casting. Then all the parts are CNC machined to specification.
 

nccole

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I am going to work on getting a picture uploaded. I have a picture of the mating surface to the pump as I see it. The picture was looking down through the center section because I could see aluminum dust in the filter and I had not yet removed the filter. It does however show one of the mating surfaces. Do they not lap this surface back to smooth?


 

ILENGINE

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They don't buff or mill them back to smooth because removing any material changes the down tension therefore the output pressure of the pump or motor. Hydrogear doesn't give flatness specs either so there is no way of knowing the tolerances. The reason the left seems to go out before the right is most people turn to the left more often.

the problem with the lower end consumer units is some are not set up with shock valves to relieve the pressure when you attempt to change direction, so if you create too much back pressure within the unit the pressure at the pump will overcome the down force and lift the pump off of the mating surface, which as the pressure is relieved slams down on the center section causing metal to metal contact and damage.
 

Mike_Goad

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To Illengine, (I hope I spelled that right)...you sir are absolutely correct. I do not see that very often on these forums.
I was a factory trainer who taught dealers how to repair Hydro Gear units.
The center section if molded using what is called lost foam molds. if you look at the outside, it looks like Styrofoam. It is then machined flat. Like Ill said, if you run your finger nail across the surface and can catch it on a grove, it is shot.
The aluminum dust is normal. as these unit run, extremely small amounts of aluminum do get worn off. it is not a concern. If you see chunks, however, then be concerned.
If I remember correctly, there is a small wedge looking piece of metal (about a 1/2" sq) that goes in the center section. this is your bypass plate.
there are parts manuals on line. make sure to use OEM parts. just google your entire model number found on a white sticker on the unit.
 

nccole

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To Illengine, (I hope I spelled that right)...you sir are absolutely correct. I do not see that very often on these forums.
I was a factory trainer who taught dealers how to repair Hydro Gear units.
The center section if molded using what is called lost foam molds. if you look at the outside, it looks like Styrofoam. It is then machined flat. Like Ill said, if you run your finger nail across the surface and can catch it on a grove, it is shot.
The aluminum dust is normal. as these unit run, extremely small amounts of aluminum do get worn off. it is not a concern. If you see chunks, however, then be concerned.
If I remember correctly, there is a small wedge looking piece of metal (about a 1/2" sq) that goes in the center section. this is your bypass plate.
there are parts manuals on line. make sure to use OEM parts. just google your entire model number found on a white sticker on the unit.

I did not see any chunks (actually, after looking at the picture on the computer, it may not look as good) and the post #5 picture shown is of the pump side of the center section. The bypass plate is on the motor side and I do still have that. After doing a little cleaning, the motor side is worse looking than the pump side shown. I am in contact with Hydro Gear and will be sharing pictures with them. Starting to sound like a new center section is in store. I have a supposedly new second unit currently on the tractor that overheats and quits working after about 10 mins. I may just pull the center section out of it and try that. I have cleaned a lot of the original seal and the original unit is close to being ready to be put back together. I need to mow this weekend though!

I am assuming that in the seal created, the pump/motor is always the "hammer" and the center section is always the "nail" due to material differences. Meaning, the pump/motor will never wear out, but the center section can have the crap beat out of it. Does your history/knowledge backup that assumption? I may still with some input from Hyrdo Gear lap that surface and try it out. If it doesn't cause damage, I am only out some time and tinkering in the garage with a second unit.

Thanks for your informed input as well.




 
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ILENGINE

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Center section is toast. If there are not grooves in the pump or motor that you can catch a fingernail in then you can reuse them. If it looks like the center section then they need to be replaced also.
 

nccole

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Center section is toast. If there are not grooves in the pump or motor that you can catch a fingernail in then you can reuse them. If it looks like the center section then they need to be replaced also.

They look pretty good, don't recall feeling any catches. The motor does look a little more rough though.



 
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