Tractor squeals under load after getting warm

[Ken Pike]

Is there some type of pressure relief valve in the system? I have a '48 Ford 8N & even it's antiquated hydraulic system has a relief valve that apparently squeals a bit when it operates.

 

[Soundguy]

for sure... and it's been discussed back in the thread..

soundguy

 

[hlukeh]

Hello Jim, Bill, Duff,

Thanks a lot for all the replies! Shortly after I asked about my hyd problems I became very busy and had to leave the country for work. Now that I'm back I'll have some time to look at this again.

I should really be paying you guys for your time. A couple of you are obviously very experienced, and your input is worth a lot.

Bill, when I changed the oil it looked clean. I appreciate the discussion about safety. It makes anyone reading this thread in the future (including me) aware of the potential dangers when diagnosing their hydraulic problems.

I've used both my hand and an infrared thermometer to try to pinpoint the source of the squeal, but it hasn't been that obvious. There are a couple places where the temperature is slightly hotter, but nothing over 110deg. F. I've got a guy coming over this week who sounds like he knows quite a bit about hydraulics and small tractors, but I'm not sure how much he knows about hydrostatics. We'll see if he can determine if it's a valve or other mechanical wear.

Thanks Jim for the diagram and for the detailed analysis. When the tractor is off, sitting on a flat surface, should there be high pressure in any of the hydraulics (I assume that if I left the loader up there would be pressure build up, but other than that I wouldn't think there would be any)? If I were to determine with my IR thermometer that a relief valve is the culprit and I decide to pull it, should I be worried about hyd fluid spurting out at high pressure, or should it just ooze out when the tractor is off?

Luke

 

[jinman]

Thanks Jim for the diagram and for the detailed analysis. When the tractor is off, sitting on a flat surface, should there be high pressure in any of the hydraulics (I assume that if I left the loader up there would be pressure build up, but other than that I wouldn't think there would be any)? If I were to determine with my IR thermometer that a relief valve is the culprit and I decide to pull it, should I be worried about hyd fluid spurting out at high pressure, or should it just ooze out when the tractor is off?

Luke

Luke, I'm not sure how you intend to use a thermometer to determine pressure, but it will tell you if there is something creating a hot spot. If pressure relief valves are opening and staying open, they will heat up, but I don't think you will be able to "see" that with the thermometer.

If the tractor is off, you won't have to worry about any pressure except if it is in the sun, external lines can heat up and have pressure that will immediately drop as they are disconnected, sometimes with a small squirt of fluid. What you do have to worry about is disconnecting a line below the level of the reservoir or trapped fluid in a line or filter and have it drain out on the floor or ground. It's not a safety issue, but certainly a spill issue. If you remove a relief valve, you will certainly have some fluid leak out. How much fluid is something I would not know.

Glad you are back home. I'll have to revisit all of this thread to refresh my memory of your problem. I don't remember as well as I used to.

 

[edsan]

I have the same problem, did you get yours fixed, mine squeals after 20 minutes and I get a vibration from the hydrostatic pedal, also I get a chatter when I try to raise the bucket, and the tractor will not move until I shut it off for a couple of minutes
Could you please get back to me.
Ed

 

[jlrsn]

edsan,
I've seen Pressure Relief Valves with a weak spring squeal and cause a chatter with rapidly fluctuating hydraulic pressure. I'd also bleed your Hydraulic System of any possible air. Someone else can jump in with their experience.
Good luck,
Jim

 

[dynasim]

I'd bet your sucking air into the inlet line.

Chris

 

[edsan]

Thank You Jirsn I will check that out.
Ed

 

[edsan]

Hi everyone My real problem is the tractor will not move after getting hot and the hydrostatic pedal gives a high pitch noise vibration when I step on it. does anyone know of this problem and what the fix is.
Ed

 

[edsan]

Hi hlukeh
I have the same problem with my 1520 4wdr. did you find the problem, could you get back to me Please.
edsan

 

[Jbrink64]

Hi everyone My real problem is the tractor will not move after getting hot and the hydrostatic pedal gives a high pitch noise vibration when I step on it. does anyone know of this problem and what the fix is.
Ed

From what you say, my experience is that the HST pump, and probably the motor are worn or damaged. There is a possibility of air in the oil. Try running it until the problem happens, then remove the HST filter, see if the oil is foamy.

 

[edsan]

Thank you jbrink64, I will check that out, if it works I will let you know.
Edsan

 

[046]

let us know if it's just low on fluids... sucking air in

 

[hlukeh]

Hi Edsan,

Sorry I never replied to you. I've been really busy lately and haven't been thinking about this. I have not gotten my tractor fixed yet, have you?

Through the winter the tractor was fine since it was cold out, and I am now starting to notice the problem again. I got a pfd of the service manual as was suggested on this forum a few months ago, and after looking through it I realized that I hadn't changed the hydraulic fluid initially. Today I replaced both hydraulic filters - the HST filter and the hydraulic filter, and drained the hydraulic fluid (~22L) from two separate drain ports. The fluid was extremely dirty - black and even silvery with metal particles. I've never seen such terrible oil of any sort - not even our lawn mower that has never had the oil changed.

After replacing the fluid I drove around our pasture in low range for about an hour dragging the blade and the tractor seemed fine. Then when I drove back up the very steep hill to the house the tractor would only make it half way up and then started whining as soon as I pressed the pedal. The tractor whines just as bad when I try to back up the hill. It's like it thinks it's in high range. I even tried taking it out of 4WD but it still just whines.

The hydraulic cooler is quite beat up. I'm not sure why because it's inside the front hood. I'm not sure if that could affect it. The cooler itself felt quite cool, but the hydraulic filters felt pretty hot but not too hot to touch.

I'm so sad, it cost $180 for the New Holland filters and the oil and I totally thought it was going to fix the problem because the old fluid was so, so bad...

Let me know if you have any suggestions.

Thanks,

Luke

 

[hlukeh]

Here are some pictures of the hydraulic fluid that came out, as well as the cooler.

Does anyone have any idea if an automotive cooler would be fine to replace this one with, assuming the inlet and outlet sizes were the same? I think replacing the cooler may be a good next step, although I know that just replacing parts isn't going to fix the problem - unless of course the problem part is replaced...

 

[jinman]

Here are some pictures of the hydraulic fluid that came out, as well as the cooler.

Today I replaced both hydraulic filters - the HST filter and the hydraulic filter, and drained the hydraulic fluid (~22L) from two separate drain ports. The fluid was extremely dirty - black and even silvery with metal particles. I've never seen such terrible oil of any sort - not even our lawn mower that has never had the oil changed.

I think your HST is self-destructing and the whine you are hearing is excessive pump or motor bypass. The looks of your fluid plus the silver particles are telling me that something is coming apart. The dark fluid is an indication of excessive heat and the particles are indications of wear. Either of those is a bad omen. Both is a sure bet that your transmission is going quickly.

I don't think I would replace that HST cooler right away. I'd first remove it and see if it was clear and allowing fluid to pass. If it is plugged up, that could be the reason your oil overheated and started the downhill progress. Also, make sure your filter mount is clear and not plugged either.

I hate to say it, but I think it is time for a transmission rebuild before it goes away completely and has to be replaced. Right now your tractor is moving on flat ground, but soon you may get stuck in the field with it because it refuses to move. I just don't think this is a simple fix from the looks of your oil and all the other symptoms.

 

[Philmorley1]

Hi,

I am not an expert but have had some similar symptoms with my kubota. are you going up the hill in the H gear range? if so that may be just too much load for the tractor in that range.
Phil

 

[hlukeh]

Haha! Phil, if I could drive anywhere except on a very flat road in high range, I would be so excited! I pretty much only drive the tractor around in Low range because it usually squeals if there is any load on the tractor in medium or high range.

Jim, you're probably right about the rebuild, but I bet my grandfather never changed the oil, so maybe the color and slight metal buildup is normal after 20+ years of light usage.

I still have a feeling that the issue has to do with a specific part since it is definitely affected when the engine warms up. I'll probably take off the cooler, see if I can blow air through the fins and see how well fluid flows through the chamber. It's somewhat suspect to me considering that the hydraulic piping, filters, etc were hot (maybe 122F) whereas the cooler wasn't even warm. To me the cooler should be hotter than the other parts since it should be dissipating heat.

You mentioned checking the filter mount for buildup. You mean where the filter screws onto the tractor? I forgot to mention that when I took off the hydraulic filter there were flakes of what looked like filter material blocking the ports which is not a good sign, and would have definitely been affecting the flow.

Thanks again for all the help you've given me!

Luke

 

[jinman]

You mentioned checking the filter mount for buildup. You mean where the filter screws onto the tractor? I forgot to mention that when I took off the hydraulic filter there were flakes of what looked like filter material blocking the ports which is not a good sign, and would have definitely been affecting the flow.

Thanks again for all the help you've given me!

Luke

Luke, I was speaking of the pressure bypass checkvalve that is normally installed in the HST filter mount. If that bypass is stuck open, you may not be sending any fluid to the cooler. I would disconnect everything, clean it and test by blowing low pressure air through it.

...and by the way. If your grandfather never changed the oil, in 20+ years, there's a good chance that the HST is completely worn out. Cool fluid would give some power, but when the fluid gets hot (maybe very hot internally) it thins out and bypasses worn pump cylinders. I don't think you will find a simple solution to your problem. It could be a pressure relief valve stuck partially open, but until you get it out and check it, you'll never know.

 

[Coyote machine]

If it were my tractor I would take the cooler to a radiator repair shop to dip it and pressure and flow test it. After verifying it was good enough to reuse then I would do what has been suggested to your probably failed HST unit and get back to work on things you actually want to do.
Good luck.