B1750 loud vibration noise linked to HST?

[Grubs]

My first post - Hello all - and my first compact tractor. A second hand B1750 HST (4WD w/power steering and bi-speed turn + MMM. no FEL.). The tractor has done 1000 hours and was just serviced by dealer before delivery but I dont know what level of service that might have been. I have no prior experience with HST tractors so I'm not sure what is normal noise and what is excessive but today (day 3 of ownership) the tractor seems to be making a lot more noise than it did on day 1.

I searched the forum and read posts about HST whine and throwout bearing noise but I dont think thats it for me.

I'm getting a very loud vibration noise, almost like the screaching of a dry bearing as soon as the HST go pedal is even slightly depressed. The noise is louder than what I would call the whine of the HST. At first I thought it was vibration being amplified by something loose on the deck of the MMM as it seem to be coming from between my legs. The noise is not there at idle - and seems loudest when the forward pedal is just ever so slightly depressed and the HST loads up to get the tractor moving forwards. Once moving along at speed the nose seems less but it might be that it just seems this way because the engine noise and HST whine is louder by comparison.

The noise is only under load (e.g. accelerating forwards) When going down a hill using the gearing to slow the descent the noise goes away completely but returns if I accelerate forwards. No noise at all at idle clutch in or out. Accelerating backwards from standing start is the same noise as I get accelerating forwards.

I had a service agent come out to fix another issue (electrical) and I asked about the noise but he didnt seem to think it was anything special given its a second hand tractor and just started mumbling about the high pressure pump of the HST. I think he was in a hurry to get to another job and was blowing me off.

I do hear the whine of the HST (esp when climbing hills) and I expect this. To my unexperienced ear the noise thats bothering me really sounds like the HST pump cavitating (is that possible?) or a dry bearing. The noise was not present when I first took delivery of the tractor and I spend a couple of hours mowing on our hilly orchard so I know what the HST whine sounds like. It started the next time I went to take the tractor out.

I have no way of transporting the tractor back to the dealer - so I'll have to pay for an on-site service call but would like some ideas from you nice people first if possible. Ideas?

Edit: I have not checked the HST filter screen and I'm not sure if the dealer did before delivery but I will be asking. Can I check the screen without dumping the fluid?

 

[B2400]

Do the filter/s look new underneath? This would indicate a proper service. Also check and make sure parking brake is not partially set as this would increase hydro whine. To check suction screen you will probably lose a significant amount of hydraulic fluid unless you tip tractor on it's side for service!

 

[Grubs]

Thanks for that.

The dealer confirmed the pre-purchase service included changing all fluids/filters. Yet I found the HST level is about 3-4" *below* the bottom of the HST dipstick. Maybe the hydro pump is sucking air.

I called the dealer and they didnt want to believe me... however... unfortunately I also found the engine oil level was 8" *above* the full mark on the dipstick and when running the tractor this morning oil came spitting out the breather. Diesel is leaking into the oil - probably a blown seal in the injector pump

Though I'm dissapointed, within 2 hours the dealer has sent out a mechanic and he's here now changing the diesel pump (and I got him to check the HST fluid level). Great level of service so props to the dealer. I'm glad I paid the extra $ to buy second hand from a dealer now. I'll reassess the noise sittuation when its running again.

 

[B2400]

Sounds like you've purchased from a quality dealer. If they fix everything to your satisfaction I'd say you have a keeper on the tractor and dealer!!

 

[john_bud]

Put that sound into the "low hydro-fluid" category for future reference.

A hydro whine 2x to 3x louder than normal is the only indication that you left the brake on.

Dealer should have it fixed up quick.

jb

 

[alchemysa]

I'm getting a very loud vibration noise, almost like the screaching of a dry bearing as soon as the HST go pedal is even slightly depressed.

There could be other sources for the noise, but you are describing HST whine perfectly. Some HST noise is normal but if you think the tractor also has poor power then a HST problem becomes even more likely. In dirt, you should usually be able to spin a rear wheel even if the tractor is halted by an obstacle.
If the tractor is moving OK then theres no need to panic but personally I'd never believe that the HST metal mesh screen had been cleaned properly unless I'd seen it myself. (I've been caught before).

If you haven't already got one, get the free a parts manual from here. Lots of informative pics... Kubotabooks.com

 

[Grubs]

Thanks for that alchemysa - I downloaded the parts manual - very handy!

I found the HST level is about 3-4" *below* the bottom of the HST dipstick.

I also found the engine oil level was 8" *above* the full mark

Turns out my dipstick readings were the key. It looks as if the hydraulic pump was pushing HST oil into the engine oil sump past a bad end seal in the pump. The mechanic spent a few hours on-site checking the fuel system but the oil wasn't thin enough for it to be diesel. He's taken the pump away to fit a new seal.

I was looking to buy a 2nd hand tractor privately to save pennies but now I'm very glad I found a supportive dealer! I drive for 20 mins past 3 other dealers to get there but they have more than earned my business.

 

[john_bud]

Sounds like they are treating you right.

Feel free to slip the mech a bit of long green. You will get paid back with better service over the years.
jb

 

[Grubs]

Closing the loop...

The tractor is back in one piece with a new seal in the hydraulic pump and all fluids back to the appropriate levels.

The noise is now a lot quieter and I now believe that despite what I said in my OP it was just the HST whine but it was a lot louder before due to (1) low HST fluid and (2) I was accellerating with the engine revs too low (near idle). I'm now increasing engine revs to 1200-1500rpm before taking off.

Thanks all for your comments.