Tractor squeals under load after getting warm

[jinman]

Good job so far Luke. Looking at the mouse-house, it sure makes you wonder why all openings aren't plugged. My tractor is the same way with ports going into the relief valves. I sure don't envy your having to clean up that mess. From the looks of things, your problem was probably that clutch slipping because of the throwout bearing being so far out of adjustment. I bet you keep that 3/4" freeplay the next time around after getting this replaced. You have to be pretty pleased that it was something simple rather than an HST rebuild. Many HST tractors also have a clutch. This is a very good lesson in why you need to keep that clutch adjusted properly even on an HST tractor.

I think it's funny how we all zeroed in on the HST. Had this been a gear tractor, many of us would have immediately said to check the clutch. I never considered the clutch because my tractor is one of those HSTs that doesn't have one. Hindsight is 20-20.

EDIT: The pressures you got during your test still indicate a problem with the HST. That and the looks of the old oil from your change that you posted have me thinking that you may have reduced performance from the HST. There are still questions that need to be answered.

 

[winslet]

Hey,
Sorry I am not understand with this.

 

[hlukeh]

I took off the clutch housing and removed the HST. The HST looks beautiful inside and the high pressure relief valve looks fine. I guess there's a possibility that the high pressure relief valve spring is slightly weaker, but because of the underlying symptom - pressure drops as engine heats up but not necessarily as hydraulic fluid heats up, points me to the clutch being the entire problem. If the clutch was slipping, then theoretically the longer the tractor ran, the more it would slip and heat up and thus the easier it would slip.

I just wanted to take out the HST and open it up to see if there was any obvious wear inside, and to see if there was any obvious problem with the relief valve, but it all looks fine to me.

I could add an extra washer to the relief valve to increase the pressure that the valve would open, but it's probably smart to replace the clutch, put it all back together, test it out, and if there is still a problem try to pinpoint the issue further and then re-take it all apart and fix the next thing that it possibly could be.

Let me know if anyone has any thoughts on the HST or relief valve.

For anyone trying to take the HST out of this tractor in the future and not being able to remove the clutch housing, the bearing going to the front drive axle, as shown in some of the attached pictures, was completely seized to the shaft and finally came loose after spraying anti seize spray (liquid wrench) around the axle and let it sit for a while. I then had to lightly tap the shaft tip with a hammer to get it to slide backwards through the bearing.

Luke

 

[SSdoxie]

Looking at the clutch it's wonder it drove at all. The valve plate on HST looks like new yet. I wouldn't change anything there, put in new clutch and throwout bearing and try it.

 

[hlukeh]

Here are some more pictures of the hydrostatic drive. It looks brand new inside!

 

[jinman]

Looking at your sparkling clean HST's inside and the dirt on the outside of the transmission, I just hope you are being extremely careful to keep any crud out of the transmission. I'm sure you will be very meticulous, but seeing the contrast in your photos makes me cringe a bit.

 

[hlukeh]

Well, my clutch finally arrived and I put it back together enough to test it out. Guess what?! It works just as well as it did before I took it apart!!!! That means I haven't made it any worse, but it still bypasses fluid somewhere and squeals around 2600psi and gets worse the longer it's driven.

A few weeks ago I bought a few implements that I got a good deal on. Yesterday I tilled a couple of acres with the rototiller and it didn't squeal at all in low range until I started tilling up a not so steel hill. The tiller runs off the PTO and actually helped to push the tractor up the hill when the tractor started losing power.

The squeal sounds like it's coming from inside the HST somewhere, but I'm not sure what else to look at in there, not to mention that it takes a couple hours to open the tractor up - draining power steering fluid, hydraulic oil, engine oil (the filter blocks a bolt)...

Luke

 

[hlukeh]

Today I decided to make a high pressure relief valve removal port instead of splitting the tractor. It was very easy to drill a hole through the housing, and I don't think it will weaken the mid section at all. I'll just have to find a nice plug to put in the opening.

I removed the high pressure relief valve, took it apart and found an o-ring that had a very slight slit in it, so I replaced the o-ring. I also added an extra washer to the ones that were already installed as spacers to slightly compress the spring. I figured I should see a difference if the spring has weakened and the issue is the relief valve.

I put the relief valve back together and back into the tractor (30min total procedure!!). There was no change whatsoever at the point that the HST started squealing with the brake on, engine running at 2500rpm, in high range, and then pressing slightly on the pedal either forwards or reverse.

Unfortunately I don't think there is an issue with the relief valve, but now I have no idea what else it could be.

Does anyone have any other ideas?

Thanks,

Luke

 

[dynasim]

I would look for air ingress into the suction side of the charge pump. It is a relatively common problem, and the specific symptom is squealing.

Good luck
Chris

 

[hlukeh]

Thanks for the suggestion Chris.

Yesterday I checked the charge pressure at the drilled out banjo bolt, and at idle it was just under 90psi. What I hadn't tried before was putting the tractor in high gear with the brake on and pressing on the pedal while watching the charge pressure. As soon as the tractor started loading, the pressure started dropping, so it appears that there is a problem either with the charge pump, charge relief valve, or as you mentioned air getting into the suction line.

I guess air getting in could be as simple as the hydraulic pipes that go into the charge pump could be allowing air past the o-rings. The two pipes that go into both sides of the charge pump are just pushed in and are sealed with o-rings and don't really have much holding them in place other than a plate and screw on the outside of the tractor. I'll have to check those seals as I didn't pay too close attention to the o-rings when I had the pipes off.

Thanks,

Luke

 

[IslandTractor]

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]

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]

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]

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]

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]

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]

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]

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]

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.

 

[hlukeh]

Woa, they have a fix now?! I haven't read the Kioti posts in a couple weeks. I better take a look. Thanks for the tip!

Luke