Tractor squeals under load after getting warm

IslandTractor · Jul 31, 2011

You might want to check an ongoing thread on the Kioti forum. A small number of DKse tractors show similar squeal noises. No one has a clear cause defined yet but perhaps you would find it useful to read. I forget the thread title but it should be obvious.

Good luck.

Ford tractor · Jul 31, 2011

hlukeh said:
Does anyone have any other ideas?

Thanks,

Luke

I hope that tractor NEVER has a FEL attached. That big hole in the bell housing will compromise the structural integrity. Don't know how much, but the hole there is making it weaker.

hlukeh · Jul 31, 2011

I actually don't think it'll make it any weaker at all because that section juts outside of the rear transmission housing and doesn't contact it at all. Also, because there is a bolt both above and below the new access hole, that section wouldn't have been adding much to the strength. I'll watch it though and see if any cracks begin anywhere in the bell housing. My bet is that if the bell housing was modeled in a program like Solidworks and analyzed for stresses through the material, there is probably little stress in that area, but of course, that's just my opinion. I'll bet that the reason an access hole was not created at the factory was to make it so dealers had to open the entire tractor to get to the valve so there was more money to be made in labor.

I'll let you know how it holds up after I put the FEL back on and do lots of work.

Thanks,

Luke

kattywumpus · Aug 10, 2011

IslandTractor said:
You might want to check an ongoing thread on the Kioti forum. A small number of DKse tractors show similar squeal noises. No one has a clear cause defined yet but perhaps you would find it useful to read. I forget the thread title but it should be obvious.

Good luck.

http://www.tractorbynet.com/forums/...176565-dk40se-squeal-when-moving-reverse.html

Currently it been confirmed by two owners, myself included, that the HST pre-charge pressure is too low. What's causing it is currently unknown. It's a long thread so you may want to read the last 5 or 6 pages which might provide more relevant information. Good luck.

hlukeh · Aug 12, 2011

I had started reading that thread after IslandTractor suggested it, but I should start at the end and work my way backwards as I didn't make it all the way through!

I've pretty much determined that it's the charge pressure too.

I've taken the charge pump apart and it's absolutely perfect. The charge pressure is good (80-90psi) when the tractor is idling at any rpm. It stays at that pressure until the fwd/reverse pedal is pressed and the tractor is blocked (or trying to drive up a steep hill or pull/push something heavy), and at that point, the squeal starts, and the charge pressure rapidly drops to almost no pressure.

It seems to me that the the issue is that either the hydrostatic begins rapidly bypassing fluid, and the charge pump can't keep up, or the charge pump is trying to suck more fluid on the suction side and either starts getting some air, or just can't get enough fluid for some reason (back pressure builds or something).

So far I have changed one o-ring that seemed somewhat worn on the suction side, but I don't like how the suction tube just presses into the charge pump and the filter housing. I'm planning on getting a length of clear tubing that I can put on the suction side to see the fluid going through it and see if there is air in it, or something else.

I better get to reading the rest of that thread first though!

Thanks again for the suggestion,

Luke

Coyote machine · Aug 12, 2011

FWIW, as far as the Kioti squeal noise, (mostly in reverse), it seems that some Kioti dealers, mine included, are saying that operating the tractor at less than 2000 RPMs influences how/when the squeal occurs. I mention this to assist in cutting to the chase in the thread about the Kioti issue(s). And, at least in the case of my tractor running at or above 2000 RPMs seems to have somewhat of an effect in reducing the squeal frequency, duration and symptoms in general. I can't say why this is so, not do I have the expertise to comment on what is a considered to be normal RPM range to run a tractor of any brand. But, tests consistency can be useful, so I throw out the idea in your direction to see if it is a factor in your testing of your HST/tractor.
Hope it helps.

hlukeh · Aug 14, 2011

Here are a few videos of the squeal. It's always right at the end of the pressure rise, and as soon as the squeal starts, the hydraulic pressure starts decreasing.

HST high pressure test port reverse 2500rpm - YouTube

HST high pressure test port reverse 1000rpm - YouTube

HST high pressure test port forwards after warming up - YouTube

I tried improving the suction tubing seals, but it didn't help. It sure seems like it's the high pressure relief valve, but I don't think it is since I increased the spring pressure and it made absolutely no difference. Too bad that relief valve is $300+ otherwise I'd just try changing it.

I think I'm about ready to put it all back together and just live with an underpowered tractor that slowly loses power as it warms up.

Luke

hlukeh · Sep 22, 2011

I think I have pretty much isolated the problem to the charge pressure dropping as soon as hydraulic fluid starts passing though the hydrostatic motor.

I took a video of the charge pressure. The first half of the video is of the charge pressure while the tractor is at a very low idle, and the second half of the video is of the charge pressure when I press on the hydrostatic pedal with the park brake on and the tractor in high gear so it can't go anywhere. The pressure drops the more I press on the pedal, and then when the hydrostatic motor starts squealing the pressure almost drops to 0.

Hydrostatic Charge Pump Pressure - while idling and then pressing pedal - YouTube

If anyone has any other suggestions as to what to look at next, please let me know!

Things I have done so far:

Changed both hydraulic filters, the suction filter and the filter after the charge pump.

I have changed the hydraulic fluid to the fluid recommended by Ford New Holland (Ford 134).

I have removed and cleaned all the hydraulic lines.

I checked all the o-rings on the suction side to make sure it wasn't sucking air, and they all seem good, although I replaced one of them.

Checked the cooler to make sure it wasn't clogged at all, and actually bypassed the cooler but it made no difference.

When the above didn't solve the problem, I separated the tractor, took out the hydrostatic drive, opened up the charge pump and it looks very good - no scoring or anything else out of the ordinary.

I looked at the charge relief spring and it looks fine (not broken but could be weakened I suppose, but if it was weakened I would assume that the charge pressure wouldn't even be able to build to 90psi).

I adjusted the high pressure relief valve (both higher and lower) to see if that could be the issue even though it's pretty clear from the lack of charge pressure that it isn't the problem, but it didn't make any difference at all so I reset it.

After doing all the above (which meant separating and re-connecting the tractor a few times) it still behaves exactly the same as it did before I did the first thing which was change the filters and hydraulic oil - the pressure still builds to 2500psi and works worse as it warms up.

Luke

IslandTractor · Sep 22, 2011

Have you tried the equivalent of the Kioti fix? I believe they replaced a hard line with a hose in some part of the system and that seems to resolve the squeal. I know you have been reading the Kioti thread on this issue but haven't seen you comment directly on that "fix" with your Ford.