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