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.