Tractor squeals under load after getting warm

[hlukeh]

I have a 4wd Ford New Holland 1520 diesel tractor which runs perfectly as long as it's cool, but once it warms up it starts squealing as soon as I try pushing/pulling anything or driving up steep hills. As soon as it squeals it completely loses power and won't go up anything or pull/push anything. It doesn't lose power power in that the engine dies, it loses power in that the all the power goes to squealing instead of to the wheels.

I'm not sure squealing is the right word, it's more like a whine that occurs as soon as I push on the pedal to go forwards or backwards with any kind of push/pull load on the tractor. The whine goes away as soon as I let off on the pedal.

It has a hydrostatic transmission, and once it gets hot from working (~1 hour) it pretty much squeals whenever I try to drive forwards or backwards up any kind of hill. The rpm doesn't seem to help the power once it's squealing, and the speed (how much I press on the pedal) doesn't seem to help either.

If I let it cool off for a couple of hours, then it'll have all it's power back and be able to pull big logs up the hill that it previously couldn't even drive up when hot...

Does anyone have any ideas of what the problem might be or where I should look? I changed the hydraulic fluid last summer to see if it would help at all but it didn't seem to. One person suggested that there may be a seal that's getting soft once the engine gets warm and that the seal may be allowing fluid to get around it. I'm not sure what I would take apart to find such a seal. There is no fluid leaking out of the engine or transmission anywhere that I can see.

I will probably find a service manual for the tractor and take a look at the transmission layout, but I thought I'd ask here in case someone has seen this problem before and knew where to look.

Thanks,

Luke

 

[hlukeh]

Here's a picture of the tractor.

Luke

 

[Scotty370]

Welcome back after your year off!! ;-) I really think you need a professional opinion! These things don't just 'heal' themselves, and unfortunately the manual doesn't have a Troubeshooting Section" that's sound related! IE "If things go 'clunk', see section 3....If things 'whine', see section 4, If things 'grind' (Oh Boy!) see section 5, and bring you credit card!!!!!
Not trying to sound smug, but I think you should get a pro-opinion before more damage might be done. Especially if it's a 'repeatable' symptom! Good Luck. Regards! ~Scotty

 

[Duff]

Ok what you have is some hydraulic internal bypass, within your hydrostatic drive. Which is making the squealing sound.

Now keeping safety as your No 1 priority, you need to work your way around your tractor, using your ears to find exactly where it is squealing from.
Also use your hands and run along the pipe work/ valves. With oil internal bypassing, it creates allot of heat, and where it is bypassing it will be bloody HOT !!
Using these indicators, hopefully you can pinpoint the problem eg relief valve, directional control valve, motor etc etc.

Please when working your way around the tractor, make sure it wont drive over you.

Duff

 

[hlukeh]

Thanks a lot for the suggestions Duff. I'll see if I can pinpoint the source of the sound, and then decide what to do depending on where it's coming from. And thank you too for the great suggestions Scotty 370... You were extremely helpful! Oh and by the way, my factory service manual for my Subaru does actually talk about noises.

Luke

 

[Soundguy]

Also use your hands and run along the pipe work/ valves. With oil internal bypassing, it creates allot of heat, and where it is bypassing it will be bloody HOT !!

I'd consider that bad hazardous advice.

presurized oil injected under the skin can be deadly.

I'd never advise someone to run their hands over hyd piping.. even at only a few hundred psi it could be dangerous.

soundguy

 

[jlrsn]

I'd consider that bad hazardous advice.

presurized oil injected under the skin can be deadly.

I'd never advise someone to run their hands over hyd piping.. even at only a few hundred psi it could be dangerous.

soundguy

This is where common sense kicks in. If there is evidence of oil leaking then do so with caution but I've run my hand over hydraulic piping and valves since instructed to do so in hydraulics school back in 1958 with system pressures in excess of 3,000PSI and in all that time I've never seen anyone injected with oil. If pressurized oil is leaking it will be evident and you use common sense and not stick parts of your body into the spray and I've trouble shot hydraulic leaks for more years than most have been around hydraulic systems.
Just my opinion,
Jim

 

[Soundguy]

I routinely work on hot 120 and 240v circuits. I'd -NEVER_ give someone advice to do so even though I've been doing it for decades.

hands are not meant to feel for high pressure leaks in fuel and oil situations. a pinhole small enough to barely leave a vapor trail will show up on cardboard nicely.. and no trip to the emergency room.

as for the hyds school back in 58? that's before osha right? I've got equipment brochurs showing rear mowers on a tractor.. no deck.. no guards.. fal in and chop you up.

that's 50's era safety...

soundguy

 

[Duff]

Ok Ok

As I said fairly straight away, Safety is your No 1 priority and yes there is allot of common sense that comes into play here.

Now we are looking for a problem that has internall bypass, not oil leaking externally. If you see oil leaking externally, then dont put your hand there.
If you have a hyd hose which has wire hanging out of it, old or cracked then dont put your hand there. ( Change your hose !!! ).

My daily work, is working with hydraulics from 3000 PSI to 15 000 PSI and phneumatics to 3000 PSI.
Finding heat differential, even slightly is how we find internal bypassing (and we use our hands ). You can use fancy listening devices, heat guns or a infrared camera, however I dont have one in my back shed and Im sure most people probably dont too.

Your tractor hydraulics usually runs at 2500 PSI, and it is hosed all around your tractor. When you climb aboard your tractor you pass right next to it, when you operate your hydraulic levers, your hands are right next to it.
So yes, people can say you shouldnt run your hands along hosing, however it is ok to park your arse right next to it on the tractor?
High pressure oil is very dangerous, and it is why you should keep all your hoses in good condition. Soon as there looking old or damaged then change them.
I have also seen many machine fire's due to burst hoses, blowing atomised hot hydraulic oil onto hot engine exhausts.

My biggest safety concern here is that you are working around a tractor which is running. Make sure the tractor is in neutral or if it only happens in gear, then make sure you are in a spot where you cannot get run over, or have tractor parked up against a big tree.
If your working around the impliments, make sure you will be in a position where you cant be crushed.


Good luck and stay safe

Duff

 

[wdchyd]

Hlukeh,

does your hydrostat trans nameplate have the brand "KYB, made in Japan" on it? look close for a good set of numbers ....when you changed the hyd oil last year was the oil super clean looking or was it dark looking.?....I have worked on these with success in the past....

Bill

 

[jlrsn]

I routinely work on hot 120 and 240v circuits. I'd -NEVER_ give someone advice to do so even though I've been doing it for decades.

hands are not meant to feel for high pressure leaks in fuel and oil situations. a pinhole small enough to barely leave a vapor trail will show up on cardboard nicely.. and no trip to the emergency room.

as for the hyds school back in 58? that's before osha right? I've got equipment brochurs showing rear mowers on a tractor.. no deck.. no guards.. fal in and chop you up.

that's 50's era safety... soundguy

Chris,
Its no wonder that you've got 24k posts! You reply without reading what was written. As I said, use common sense even with your reply which was a knee jerk reaction to a conclusion of what you thought I wrote. I never said to put your hand in a spraying leak. I said If pressurized oil is leaking it will be evident and you use common sense and not stick parts of your body into the spray and I've trouble shot hydraulic leaks for more years than most have been around hydraulic systems. And what is so dangerous about working with working on hot 120 and 240v circuits. I've done it for years since long before you were born!. Again use common sense. Nowadays so many people lack it.
Jim

 

[mmurphy]

This does bring up the point the navy boys would tell stories of how they knew there was a steam leak of about 1000 psi, but could not see it.They learned by taking a broom stick to pass around piping or what ever, and if part of it fell on the floor, they knew about where the leak was at. I was told if you tried running your hand by it, it would cut your hand off and cotterize it all at the same time. I am going to take there word for it.

 

[Soundguy]

Chris,
You reply without reading what was written.

I read what you wrote.. you did not read what I wrote.

a high pressure pin hole leak can barely leave a vapor trail.. IE.. hard to see.. but enough to do skin damage.. however.. a piece of cardboard will find it as the oil accumulates for a second.

By the way.. here's a pic of 50's era safety thinking

At this point I'll bow out of the conversation...

 

[jinman]

Luke, your transmission has a high pressure relief valve that lets the transmission stall if the internal pressures get too high. This is what you feel and hear when you have your HST in too high a range and depress the pedal. I'm not sure, but I think your tractor has three ranges and neutral. Did you mention what range you are in when your hear the "squealing"? Does the squealing occur only in the high range, and does it occur in reverse as well as forward? If you can shift to the low range and your tractor has enough pull for your job, it might just be that you need to do work in a lower range when your oil heats up.

My feeling after many hours on a HST tractor is that you can always get more pull out of a cold HST than a hot one. When fluid become hot and thins out, the transmission will stall somewhat easier than when the fluid is cold. In situations where you are in a high range and there is less flow and more torque required, this is where a small leak in a relief valve will be the most noticeable, whether it is normal relief valve lifting or a small abnormal leak.

Your transmission diagram is attached below. Your transmission has a "charge" pump (items 20, 21, 22) that takes fluid from the reservoir and feeds it at low pressure to the main HST. This pump just ensures that the HST does not cavitate under heavy pumping. Inside your HST, there is a relief valve (item 7) that opens to relieve the high pressures. I beleive it works in conjunction with the check valves (items 4, 5, 6). There is one check valve for forward and another for reverse. Any of these valves or a worn internal pump could be the reason for HST stalling when it gets hot.

Normally, check valves and high pressure relief valves are removable from outside the tractor transmission casing. HST transmissions are normally mounted inside the running gear of a tractor with access to the valves being round holes visible on the sides of the outside casing. I'm not suggesting that you start pulling valves without knowing what you are doing, but rather that the valves can be inspected and pressure tests can be done at a dealer's service department without tearing your tractor apart. They can analyze your HST's performance and let you know if there is a need for service. That's what I would suggest since you are not an HST expert and could easily get yourself in over your head on a job like this. I just want you to have a good outcome and grasp of what you need to do.

One other thing... If you have an HST cooler in front of your normal radiator, make sure it is clean and able to cool the oil to the best of its ability. Your oil should be warm to hot. My HST oil reservoir which is the same as my main hydraulic reservoir will get to 150 to 180 degrees in normal heavy summer use. I use a handheld IR thermometer to measure the temperatures on my tractor.

 

[wdchyd]

Luke,

Jinman's correct that it could be relief valve squeal....and that can be remedied from outside housing......but It's possible that the Hydro/trans needs to be rebuilt.....the breakdown from Jinman is just like the KYB I rebuilt few months ago....if you decide to pull it and rebuild it you need to be pretty good mechanical (or a BIL or somebody)...or you'll need to find someone in your area with some knowledge of precision lapping on piston pumps....not your typical "Leak Fixer Guy" but somebody with a good eye to check wear on valve plates, piston shoes, rotation group and charge pump parts....

A lot of times dirty oil or trashed internal bearings can set off a chain of events internally to "Wear out" precision surfaces that can be lapped, cleaned resealed and put back into service...

be prepared to do ultra clean work if you expect great results!!

If you do go ahead with that myself or others here can talk you thru it but you will have to be diligent to be clean and priming case ports are essential to proper start-up......once again don't try this if you're not use to doing this type of work because failure could be more costly than just getting a reman unit....

 

[wdchyd]

BTW Jinman,

Excellent breakdown sheet:thumbsup:, where'd you get that from

Bill

 

[jinman]

BTW Jinman,

Excellent breakdown sheet:thumbsup:, where'd you get that from

Bill

Bill, you and I are sure "pullin' the same train." Your advice is spot on about overhaul. I want to make sure Luke needs overhaul and this is not a case of using the improper range and/or depressing the HST pedal like an accelerater pedal. If he is confident that his transmission is failing, I think pressure testing could identify just how severe a problem he has.

The diagram I posted is from messicks.com. Messicks is a terrific source for parts diagrams and pricing info on repair parts. For example, the relief valve for Luke's transmission is about $350 if I remember correctly from this morning when I saved and posted the diagram. When you go to messicks, you can select NH, Case, or Kubota and type your model number into a box. I'm not sure about Kubota, but the NH list will allow you to select the tractor and then a list of system diagrams will appear. These are from the IPC for the various systems. Choose a specific diagram and a list of parts will appear on the right with a description, availability, and stocking level. Messicks is a terrific source for info and parts. I've found their before-shipping prices to be the best around and they quickly ship your parts to your door. Nice!

 

[wdchyd]

Jim,

Wow, gotta check out Messicks.com tonite....I love breakdown sheets like these cuz the local dealers around these parts hold on to their "Interests" very tightly.....I'm just a repair guy taking work away from them (Until they need something from me:laughing::laughing:...

One of the problems Luke will have with testing on his machine is the Hydro Pump and Motor are one unit....(Cannot run flow meters between components to test).....may have to tear down anyways.....hopefully not but when do you just give up playing and get down to business and dig in...

The unit we rebuilt we changed valve plates (#15 & #15a), lapped barrels,pistons,new bearings, seal kit and go....:thumbsup:

Customer brought it in as basket case and saw nothing wrong with the wear on the critical surfaces....after we were thru it was back to climbing again...his unit had the same symptoms as Luke.....

Best would be to find proper test procedures as you suggested...I'm sure there must be ports to check charge, case and high pressure before he gets too deep...

We have an Exmark Mower in our shop right now with shot hyd system (thats what happens at 900 hrs when you don't change oil and filters) He needs complete OVH on every component....at least Luke has one component to contend with....

 

[TractorRob]

...By the way.. here's a pic of 50's era safety thinking ...

YIKES!

 

[Soundguy]

now you wonder why things like osha came into existance....

30's thru 60's era technology was good and solid mechanically speaking.. but had lots of open flywheels, belts, chain and gears.. and well as you can see.. Blades!

soundguy