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Any lawn mower mechanics here?

Freebird

By Freebird
in Watering Hole

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Freebird

Freebird

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OK....we have people here that know something about a lot of things so decided to see if there are any lawn mower experts.

 

The mower is a Snapper zero turn. It uses Hydro-Gear pumps and motors for the drive. It is not an integrated transmission. There are two Hydro-Gear pumps, one for each side. The Hydro motors and not integrated into the pumps. There are hoses that go from the pumps to the motors.

 

I was mowing a couple of weeks ago when suddenly the left lever seemed to lose pressure. It still works and I can use it but while you feel decent pressure on the right lever when you move it forward and backwards, the left lever has almost no feedback/pressure. It is also slow to respond. The left wheel does work in forward and reverse but doesn't seem to have much torque. On a long straight run, the steering seems to work OK but if I am turning on a hill or something, the left doesn't seem to have near enough torque.

 

So far all I've done is change the Hydro filter and tried bleeding the system. Nothing has made any difference. Does it sound like a bad Hydro pump or the Hydro motor? Running or not running, the right side seems to have pressure when you move it back and forth but the left side has almost no resistance to moving. Also, whether it be the pump or the motor, can they be repaired? I tried looking up parts and/or exploded diagrams on line but all I've found is the complete units at about $450.00 each.

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Monty

Monty

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I used to be a Snapper Technician, a few years back. I think you have air in it. pull the cap off the tank, start it, and work the lever back and forth slowly several times. Does it whine excessively? Are there an excess amount of air bubbles in the reservoir for that side? Compare the two.

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barend

barend

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Don,

Not familiar with the snapper, but mine have what looks like a shock attached to the steering mechanism (like on a SUV rear window) Had one one time that broke (many years ago) that caused a steering steering problem, also check all your linkages and make sure none are bent. As monty says, air in the line is possible but you should (have) be(en) able to hear that with excess whine especially under load. i.e. check your fittings. Mine have a single reservoir hydro oil, so make sure all couplings are set up so any air can flow out of the lines into the reservoir.

Rebuilding these puppies is about as costly as new ones so don't bother. also if you replace one you will not have a matching set so you may have to deal with that.

 

Warranty? Most homeowner units carry 2 years! If you have a good dealer you may be able to get a loaner while they fix yours, if you take it to a big box store they'll sent it to a wholesale fixer in whom I have no faith whatsoever.

 

Good luck!

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Monty

Monty

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A few more things to check. I haven't looked at one of these in a few years, so bear with me.

 

Is the belt tight on that side? It could be slipping.

 

Is the pulley turning the same speed as the shaft? Could be a sheared pin.

 

Each side has a release lever, to allow it to freewheel. Make sure the lever is where it's supposed to be.

 

Could be trash in that sides' tank or line, not allowing enough fluid to the pump.

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Freebird

Freebird

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Thanks for the replies. I've tried bleeding it to no avail. The two pumps share a reservoir and filter and it tees off the filter for each side. There are bleed screws on each pump that you loosen then move the levers forward and backward slowly to bleed the air. I've done that an excessive number of times and it doesn't help. Both pumps share a common belt. There are pulleys under the more, one for each pump. One belt goes around the pulley, to the pulley on the motor. It appears to be tight and not slipping.

 

I have not drained all the oil from the system. I guess I can do that and try to flush it out and re-fill. Not sure how to go about flushing it out though.

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flb_78

flb_78

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I wonder if there's a way to do a case drain test on the motor and pump. I know in the most of the hydraulics we use, you can pull and plug and check the leakage of a motor and/or pump doing this test.

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flb_78

flb_78

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Just for shiggles, is it possible to swap the pumps or the motors side to side to see if the other side becomes weak? If you can swap the motors and the left side stays weak, its the pump. If you swap the pumps and the left side stays weak, it's the motor.

 

or if they're close enough, you could just swap the lines side to side.

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Freebird

Freebird

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Only one tank and one belt? Which model is it?

 

http://store.wisesales.com/snapper-hzt21480bv-zero21480.html

 

Just for shiggles, is it possible to swap the pumps or the motors side to side to see if the other side becomes weak? If you can swap the motors and the left side stays weak, its the pump. If you swap the pumps and the left side stays weak, it's the motor.

 

Possible but a lot of work. They are reversed. Looks like you would have to pull both, disassemble them and then reassemble them reversed out how they are.

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wes0778

wes0778

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Just a shot in the dark:scratchchin:, but are the control levers connected directly to the spool in the control valve? :think:Or, does the lever push on a spring that then moves the spool? If the latter is the case, maybe the spring has broken. :confused24:

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wes0778

wes0778

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Is there a break down on the control valve(s)?

Edited by wes0778
correct spelling
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Freebird

Freebird

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Just a shot in the dark:scratchchin:, but are the control levers connected directly to the spool in the control valve? :think:Or, does the lever push on a spring that then moves the spool? If the latter is the case, maybe the spring has broken. :confused24:

 

No, square end on the shaft with a metal plate with a square hole. I checked to make sure it wasn't slipping.

 

Is there a break down on the control valve(s)?

 

I've looked everywhere and not found one. Haven't found any kind of parts list or anything else for the pumps, only complete units.

 

Do you still have the old filter? If so, you could take it into any shop that does hydraulic work and have them cut the filter open to check for metal particles.

 

Yes, I still have it. Poured out and strained the oil when I changed the filter and saw nothing. I now that is not definitive but I think I would have seen SOMETHING.

 

It's a shot in the dark, but...

 

On the wheel motor (#18 in the first drawing), there is a woodruff key. If it was sheared, the axle could be slipping.

 

Hey, it's worth checking out.

 

I thought about that but even not running, the left side just almost flops back and forth but the right side has pressure to moving it back and forth.

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wes0778

wes0778

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No, square end on the shaft with a metal plate with a square hole. I checked to make sure it wasn't slipping.

 

 

 

I thought about that but even not running, the left side just almost flops back and forth but the right side has pressure to moving it back and forth.

 

But is there a spring inside the valve body behind that square shaft? may even be a leaf type spring that in conjunction with hydraulic pressure furnishes "feedback" to the handle.

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Thom

Thom

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i may be wrong but i think each side has a high pressure relief valve. could be a broken spring.

i kinda agree , i use a pipe 't' with a pressure gauge to tell if anything is wrong , just put between the pump and motor and take a pressure reading , can also be used on the return line to check for blockage , i bought the pressure gauge and 't' from tractor supply

thom

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Freebird

Freebird

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But is there a spring inside the valve body behind that square shaft? may even be a leaf type spring that in conjunction with hydraulic pressure furnishes "feedback" to the handle.

 

No spring behind the square shaft. There is a spring though that connects between two tabs that does what you are suggesting though. It is find. In fact, I like to never got it back on.

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saddlebum

saddlebum

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Posted (edited)

You could have a faulty relief valve either broken spring or debris in the valve causing it to stick open.I doupt the filter is an issue since both pumps are tee'd off the same filter. I would get a preasure gauge 3000 PSI and tee it into the line coming off the Pump and see what kind of preasure you are getting when you activate it. most hydraulic pumnps produce about 1000 to 1400 psi for most applications though for something as small as an amphibious lawn mower it may be a bit less. take a reading from one side and compare it with the other side. unless you can find actuall specs for it. P/S most hydraulic pumps have a label indicating there max working preasure.

I don't see any hydraulic valves in the pic's but if they are used also check the preasure going in and coming out of the valve when you activate it. some hydraulic valves also use a relief valve so as to controll max delivery preasure.

Edited by saddlebum
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