3-Point Hitch Newbie Hydraulic Question

[jinman]

In the hot summertime, I measure the hydraulic reservoir temperature at 175-185 degrees F. That's a lot hotter than the water in your house and very uncomfortable to the touch. It's well within the hydraulic fluid's temperature range though. I think in general numbers, you can expect hydraulic fluid to be 75-100 degrees above ambient outside temperature. HST transmissions seem to heat the fluid up more than gear transmissions.

BTW: You didn't mention how fast your lift drops. If it drops completely over a few minutes, then you have a serious leak. If it drops over a few hours, it is leaking, but not a huge amount.

 

[mja20]

In the hot summertime, I measure the hydraulic reservoir temperature at 175-185 degrees F. That's a lot hotter than the water in your house and very uncomfortable to the touch. It's well within the hydraulic fluid's temperature range though. I think in general numbers, you can expect hydraulic fluid to be 75-100 degrees above ambient outside temperature. HST transmissions seem to heat the fluid up more than gear transmissions.

BTW: You didn't mention how fast your lift drops. If it drops completely over a few minutes, then you have a serious leak. If it drops over a few hours, it is leaking, but not a huge amount.

Thanks for the info Jim. The lift drops almost immediatly when i shut it down.

 

[Jerry/MT]

Hello I am new to the tractor scene and need a little assistance. I have a 86 Ford 1910, my first question is when I shut off my tractor is it normal for my 3pt hitch to drop all the way down. Next is it normal for the tranmission and PTO to get very hot during bush hogging. Here is exactly what happened, I had to drive about 45 minutes across the lease before arriving to the spot I was going to cut, immediatly after getting there I started cutting in some pretty thick brush for aprox 1 hr. When I was done I shut down the tractor and noticed excessive heat coming from the transmission housing. I also heard a hissing noise coming from the top of the rear diff. After investigating the hiss I found it was some sort of relief valve. The PTO shaft was also very hot to the touch. I check the fluid and its clean and has the proper level. Any help would be greatly appreciated.

P.S. I am in South Louisiana and the temp that day was about 98 F. 100% Humidity

First of all you were working the tractor hard in very high ambient conditoions,(98°F is considered hot but in may not be considered that where you are from!)) The transmission is not 100% mechanically efficient, more like 90% or less. The 10% or more loss in efficiency shows up as heat in the transmission so your drive line fluids can get plenty hot, especially when they start out at 98°F. That's normal. Hot fluid also means the casing is hot as is anything else bathed in the fluid.

Secondly, there is probably condensed water in the fluid. When the fluid gets hot, the water vaporizes and the air in the compartment get's hot too. The hiss you hearing is probably from the vent for the rear axle/hydraulic compartment which is most likely under the seat. If you hear the hiss when the three point lift is raised and the tractor is running then it could be a stuck open relief valve in the hydraulics but if you hear the hiss with the tractor shut off then it' s most likely the hydraulic compartment vent. Make sure that vent stays clear because otherwise the pressure can build up in the compartment and blow some seals.
As far as the lift dropping, it depends how fast it drops with an appropirate load on it. If your load is rated at 1000 lbs don't expect it to hold up a 1500 lb weight. It may open the relief valve and not hold that when the tractor is running. It's normal for the three oint hich to settle when the tractor is shut down with a weight on the hitch. If it rops imeditely, you have a leak somewhere. It could be some crud in the relief valve holding it partially open or it could the piston seal on the lift cyinder. If you hear a kind of screaming noise with a load on the three point and the tractor running, that could be a partially open relief valve. A modern tractor with aproperly functioning hydraulic system might settle in anywhere from 15 minutes to 24 hrs or longer.
Obviously a 15 minute drop indicate more leakdown but it still maybe acceptable. On my TO-30 Ferguson 15 minutes is considered acceptable sealing.

Hope this helps you.

 

[mja20]

First of all you were working the tractor hard in very high ambient conditoions,(98ｰF is considered hot but in may not be considered that where you are from!)) The transmission is not 100% mechanically efficient, more like 90% or less. The 10% or more loss in efficiency shows up as heat in the transmission so your drive line fluids can get plenty hot, especially when they start out at 98ｰF. That's normal. Hot fluid also means the casing is hot as is anything else bathed in the fluid.

Secondly, there is probably condensed water in the fluid. When the fluid gets hot, the water vaporizes and the air in the compartment get's hot too. The hiss you hearing is probably from the vent for the rear axle/hydraulic compartment which is most likely under the seat. If you hear the hiss when the three point lift is raised and the tractor is running then it could be a stuck open relief valve in the hydraulics but if you hear the hiss with the tractor shut off then it' s most likely the hydraulic compartment vent. Make sure that vent stays clear because otherwise the pressure can build up in the compartment and blow some seals.
As far as the lift dropping, it depends how fast it drops with an appropirate load on it. If your load is rated at 1000 lbs don't expect it to hold up a 1500 lb weight. It may open the relief valve and not hold that when the tractor is running. It's normal for the three oint hich to settle when the tractor is shut down with a weight on the hitch. If it rops imeditely, you have a leak somewhere. It could be some crud in the relief valve holding it partially open or it could the piston seal on the lift cyinder. If you hear a kind of screaming noise with a load on the three point and the tractor running, that could be a partially open relief valve. A modern tractor with aproperly functioning hydraulic system might settle in anywhere from 15 minutes to 24 hrs or longer.
Obviously a 15 minute drop indicate more leakdown but it still maybe acceptable. On my TO-30 Ferguson 15 minutes is considered acceptable sealing.

Hope this helps you.

Thanks Jerry. That definitly makes sense. I appreciate everyones input.

 

[JC-jetro]

BTW would you know what I should expect to read if I shoot the Trans housing with a IR thermometer after a good running?

I never actually measure the transmission temp but it was nice and hot. Could touch it for a few second only. I'm sure it was below 160 degrees, the suction and discharge hyd oil quite hotter. take a look at the link below.

JC,


http://www.tractorbynet.com/forums/new-holland-owning-operating/179639-how-much-temp-too-much.html

 

[jimmysisson]

If your lift piston leaks so much it drops immediately, doesn't it make sense the pump is working hard all the time to keep it up? If the mower is set in a position where the 3 point is holding the front up (most likely) that would be working the pump a lot. Better tend to that seal.
Jim

 

[jones6780]

I would think that the pump always pumps the same volume of fluid, RPM Dependent, whether there are leaks or not.
Russell

 

[JC-jetro]

I would think that the pump always pumps the same volume of fluid, RPM Dependent, whether there are leaks or not.
Russell

A true statement, a heavily leaking system is actually easier on the pump as it can not bring up the pressure. The hydraulic here is "live" as the pump runs as long as engine is running.

JC,

 

[jinman]

The pump constantly pumps fluid, but at a very reduced pressure and high volume in any open center system that is not under load. The problem with the 3PH leaking heavily is that if the tractor has an implement like a boxblade attached, the pump is constantly going from low pressure to high pressure as a function of the 3PH control valve. So the pump is loaded...unloaded...loaded...unloaded...loaded, etc. It's constantly shifting from low pressure to high to have enough pressure for the implement lift on the 3PH. If it's an unloaded 3PH, nobody usually cares if it's at the top of bottom, but anytime the 3PH lift arms are loaded with an implement, the pump is doing extra work. On a properly sealed system, the pump goes high pressure until the control valve is nulled out and then the 3PH goes into a hydraulic lock while the pump and system go back to low pressure operation. That's why you can raise a FEL if you have one while the 3PH is holding up an implement. With the leaky system, if you have a FEL, you would see the 3PH drop dramatically when the hydraulic flow was being used by the FEL.

 

[Soundguy]

i agree withJC.

3pt drop is very likely a leaky oring.. that's the hiss you hear at shutdown. oil lekaing. mind you it could ALSO be other leaks.. like a lekay relief, check or safety valve. bototm line.. SOMEthing is leaking.

as fo rthe heat. an hours worth of hard work, after a 45minute drive on a 98' day? i'd expect something to be hot too!

make sure it has the proper oil at the proper level and make sure no hyd remote ports are kicked in to operate.. past that. it's got a internal leak.. not a huge deal to fix or ignore as long as the pump makes enough flow to overcome it when running..