HydroGear ZT-3100 Cavitation problems!

Lawn wife

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We have a Snapper Pro s50X. The left side Hydro Gear pump developed what acts and sounds like cavitation problems and we can't seem to get the air out. We've done the purge procedure over and over but it is only a temporary fix. Husband is an experienced mechanic, but lawn mowers are not his thing(he builds and drives race cars). He's had the pump completely apart twice now and we both have inspected everything with a fine tooth comb. It all looks perfect! I tried to call Hydro Gear for some help, but the tech support guy is out of town, so no help there. The problems started when the motor blew up. We bought and replaced the motor ($1600) which now runs great except that can't turn left anymore. Please help, we are at our wits end. I will supply any additional information that anyone requests. We have checked all the external stuff, belts, pulley, brake release, etc...

Our grass is tall(2 acres) and only getting taller!
 

bertsmobile1

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Are you purging at the lowest speed that the engine will run ?
If the tranny is pulling big revs the oil foams so you can not get all the air out.
Nothing to stop you purging on the bench if you have a source of rotation around 1000rpm.
On some occasions I have needed to resort to applying a vacuum with my sump pump to get trannys to purge completely.
On the ones without an overflow I used a rubber cork in the breather or filling plugs.
Had a Husky Rider Pro took all day to purge once I was getting really close to writing the tranny off.

And the $ 60,000 question is what exactly did you do to it ?
Some units can be assembled backwards.
Vanity prevents me telling you how I found that out.
Some times it is good to have an apprentice that you can blame when things go wrong & the customer is at the door waiting for their mower :mur:
 

ILENGINE

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I am wondering myself why the left side drive quit because the engine blew up. Something not assembled right on the drive belt causing belt slippage under load. And now since the drive has been disassembled has the charge pump cover been rotated 180 degrees causing the pump to now operate in reverse. Or is the pump and drive actually damaged and you are missing it. Like any grooves in the mating surfaces between the charge pump and housing, pump and center section or center section and drive motor that you can catch a fingernail in will signify that the parts are failed/damaged.
 

Lawn wife

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Husband says that the transmission was getting bad before the motor blew up, so I explained it wrong. It was low on oil(bad we know!) so air got in there for sure. He is sure that the belts are correct and in good condition. We inspected all the surfaces for scratches and couldn’t find anything. Surfaces are clean, smooth and shiny. We had tried swapping the charge plates to the right side to see if the charge plate was bad but it didn’t fix it. Right side worked fine, left side has same issue. So, it seems he’s putting the charge cover on correctly. I know that’s a common mistake.

We will continue to try purging the system using the idle speed. How can a vacuum be hooked up to it exactly? We have the overflow type set up. Also, if it needs purged all day long, is there a easier way to do that besides sitting there doing it manually?

I can’t believe how much I now know about this system. I feel smart and stupid at the same time. Thank you for your advice, it’s appreciated.
 

Lawn wife

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We are continuing to purge today in hopes that the unit will improve. I have one more question. Is the growling/whining noise symptomatic of air trapped in the system, as my husband believes? Or would it sound this way in other conditions(such as unseen damage inside that is un-repairable)?
 

ILENGINE

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A more high pitched whine is normal for most hydraulic system pumps. the deeper growling type noise is more common with internal damage. The drive shouldn't be that hard to purge. Jack the wheel up, pull the bypass and start the mower at idle. Move the lever forward two or three times each direction for 10-15 seconds both directions. and then close the bypass and repeat the back and forth motion and see what happens. If no movement then I would suspect that there is internal damage that would require either replacing the internal components or replacing the entire drive.
 

Lawn wife

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Thank you to everyone who responded. The mower is fixed now! Husband purged it on the bench and finally realized the charge plate was indeed backwards. I know, I know, he had insisted it was put back on correctly. The bench purge thing helped him figure this out so again...Thank you!

It is running like a champ.
 

bertsmobile1

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Thank you for coming back .
He is not alone there would not be a single person who has not put one in backwards particularly when you only do it once in every blue moon.
 
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