M6800 hydraulics overheating

[awhite]

Kubota M6800 4x4 hydraulics are overheating! Seems to work fine when cold, but after running for several hours, it seems that the hydraulics get extremely hot and the pressure decreases on the hydraulic system. Also the rear end gets so hot that you could literally fry an egg on it. Tractor has BushHog M446 loader and 900 hrs. Changed hydraulic oil and filters ~ 850 hrs. hoping to fix problem. No luck. Anyone have and advice?

 

[art]

You have a restriction or depending on the plumbing of the loader you may have something staying under pressure.

Has the problem been there since the beginning of the loader mounting? Are there any other changes to the factory hydraulic system?

How long has it been since the radiator area has been cleaned?

 

[awhite]

Loader has been on tractor since we bought it new. I just cleaned radiator last night. The bottom half of it was almost completely stopped up. Could this make the hydraulics overheat this much?

 

[J_J]

If you were to tee in a gage, with the pump, and with no valves operating, there should not be much pressure on the gage. If there is a restriction anywhere from the pump to reservoir, you will see pressure, and the hyd fluid will get hot. Places that cause heat are QD's, relief valves, hyd radiator plugged, incorrect hose size. A straight hose has the least resistance, anything else will cause some heat, so less fittings is better.

 

[Egon]

The bottom half of it was almost completely stopped up. Could this make the hydraulics overheat this much?

Yup!

 

[awhite]

Used WS stumpgrinder yesterday for about 2 hours and still seems that the hydraulic fluid is still getting hotter than it should. Also the auxiliary remote detent will kick out fine when cold, but after warming up you have to run the tractor at or above 540 rpm for the detent to kick out either way. While baling hay this week (NH BR 730) I had to use a rag to remove the rear hydraulic lines from the tractor because they were so hot that you could not hold them with your bare hands. Also when the baler would get almost full; with the tractor in low first, 4x4, and full throttle, it would idle down so much that you had to kick off the PTO to keep it from dying. There's something bad wrong, but I don't want to go replacing parts. Could the hydraulic pump be going bad? I've been told that mechanical pumps hardly ever go bad.

 

[kthompson]

I have a M6800 and yes the hyd fittings can get too hot to handle. But it seems you have an issue.

Did this start all at once? Or over time? Had you changed hyd filters not too long before this began? Did you use Kubota filters? How about your air filter? It can cause your engine to run hot and lose power. You brakes are releasing?

Does your temp gage show the engine running hot? You said you cleaned your radiator, are you sure it is fully clean? A leaf blower works good.

If i understood it is happening regardless of what implement you are using, correct? So that would rule out implement being the problem.

 

[awhite]

Checked pressure at rear remotes according to Kubota shop manual. Readings are right (~2700 psi) when engine is cold. After engine warms up readings fluctuate between ~1500-2000 psi. Could pump be bad?

 

[J_J]

Checked pressure at rear remotes according to Kubota shop manual. Readings are right (~2700 psi) when engine is cold. After engine warms up readings fluctuate between ~1500-2000 psi. Could pump be bad?

Can you explain how you tested the system?

Do you know if the reliefs are working?

Bad pump is a broken pump. A weak pump is caused by wear, and will slowly get worse.

 

[art]

You have a hydraulic valve malfunctioning.

I don't know why or which one but what you have sounds like you are building pressure some where in your tractor causing the system to be under stress.

 

[Wayne County Hose]

You need to install a hydraulic oil temp gauge. "Too hot to hold" is not an accurate reading. Your o-rings and seals are rated to 212 degrees. If you're running at 180 you are still 32 degrees below max but still too hot to hold. It does sound like you are working the snot out of this tractor. I'm not familiar with your model so I don't know if it's a homeowner model or industrial model. BTW, there is a big difference between the two.

Andy

 

[awhite]

I checked hydraulics again this evening with the tractor cold. The gauge would go all the way to ~2700 psi then it would fluctuate between ~1000 psi and ~2700 psi. To check the hydraulics I insert a QA into one of the rear remotes and set the engine to maximum speed (it recommends that the fluid temperature be between 113-131 degrees F). Then I engage the remote lever and read the pressure gauge when the relief valve is actuated. Could the relief valve be malfunctioning?

 

[J_J]

If the pressure reliefs are working, then the pressure should be good, because they only relieve at the set pressure. Is it relieving at 2700 psi? If you are not working the system hard, the pressure will not stay high. With the tractor running, and no levers activated, there will be very low pressure. If you raise an empty bucket, you may see 500 to 1000 psi. If you have a full load, you may see 2500 psi. If you hold the levers full forward or full back, then the reliefs will go off, and you will read relief pressure. If the reliefs are being used a lot, then the fluid will get hot. If the relief valves fail closed, you could damage your pump. If the reliefs fail by staying open due to trash, you will have low pressure.

 

[Leejohn]

I just looked at the parts brake down for the high pressure lines and there is a coupler just down stream from your pump.Check and see if you can Tee there so you can put the gauge there it well tell you more. Up to 2700psi and down to 1000psi seem like alot of differents. I would check the steel HP line and make sure its not smashed. If not pull the main relief and have a look, also while there put a new spring in it if your dealer has one.

 

[sallymander]

You need to install a hydraulic oil temp gauge.

I had a MF whose hydraulics ran real hot after several hours of using a continuous hydraulic motor on hot days. System was fine, just overworked.
Installed one of these so I could rest the tractor when things got hot rather than ruin my hydraulic fluid.
Cyberdyne Electronic LED Digital Transmission Temperature Gauge : JC Whitney: Auto Parts & Accessories

 

[awhite]

Noticed yesterday that detent on rear hydraulics won't kick out now. Also it sounds like the hydraulic pump is starving for fluid because now it's whining when FEL cylinders reach end of their cycle and when the rear hydraulics are in the detent position.

 

[J_J]

Noticed yesterday that detent on rear hydraulics won't kick out now. Also it sounds like the hydraulic pump is starving for fluid because now it's whining when FEL cylinders reach end of their cycle and when the rear hydraulics are in the detent position.

That sound you hear when the cylinders are at their limit, is the relief valve going off, and the pump is working hard. If you put a pressure gage on the cylinder hose, you can see the pressure in the operating mode, and then you will see the relief pressure when you hear the sound at the cylinder limit. The pressure you see on the cylinder gage will vary by the load in the bucket. An empty bucket being raised, may only show about 500 lbs, but as soon as you hit the limit, you will see relief pressure. Rules are rules.

What are you using on the back, that requires the valve to be in detent mode? If you are using the PB port on the FEL. and you set the rear valve to detent, the fluid is going through the FEL valve, back to the rear, but as soon as you activate a lever on the FEL, it interrupts the fluid going to the back, because it has priority and uses it for the FEL. This is assuming that you are using the PB port. A detent valve lever, should not come out of detent until you manually move it, except on log splitter valves , which are automatic.

 

[awhite]

Finally solved problem! Pulled hydraulic pump and one set of the gears were seized up. Have no idea how this could have happened. New pump on the way.

 

[ShawFarms]

My 09 m6800, 4x4, factory loader, hydraulics overheated today, using15' bushwacker batwing, grass fence high, ran in 1st, max rpm, 4hrs, notice heat, got a little hard to stear, shut down, back of tractor to hot, could here fluid boiling, Do I need to clean radiator, changeengineoil and HUD fluid? Is tractor supply fluids as good as kubota's? Thanks Bo

 

[CJONE]

I would start a new thread with your question. But if you literally boiled the fluid, I would change it and your filters and find out why it got that hot. CJ