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MF 390 PTO not engaging after gulp of air.

G

Grim

New User
My MF 390 will not engage the independent PTO (hydraulic PTO clutch). The rear axle/hydraulic oil level was showing low on the stick. I was working backwards on a very steep slope & the power steering locked for 3 sec, 3 times. Guessing pump took a gulp of air due to low oil level. Topped up oil & all ok except PTO. Diff lock & 4wd on same hydraulic circuit all working. Any thoughts without splitting tractor? Cheers Grim Australia.
 
Yes the PTO was running a mower (slasher) at the time. I
headed back to get oil & it continued mowing for about 200
metres or so. Then I noticed it had stopped. If you engage the
PTO from the cab it "slowly" comes up to speed but there is no
power in the drive. Thanks for your interest. Grim
 

It sounds like you probably "cooked" the clutch pack. These clutch packs are usually held engaged by hydraulic pressure, and a major drop in pressure for more than a split second will allow the clutch to slip which can burn the facing off the discs pretty quickly. I am not familiar with the 390, but PTO clutch repair usually involves a rear split. The discs themselves shouldn't cost a lot, the seals should be replaced at the same time.
 
Thanks again for your support. From your experience is there
any way to prove that it is the clutch? Or at least a good
possibility as a tractor split is a major & then to find it was not
the prob. Just a thought. Cheers Grim
 
(quoted from post at 15:22:23 10/27/14) Thanks again for your support. From your experience is there
any way to prove that it is the clutch? Or at least a good
possibility as a tractor split is a major & then to find it was not
the prob. Just a thought. Cheers Grim
Click to expand...

Yes find out what the hydraulic pressure is supposed to be, then take readings and see what you get with the PTO disengaged and then when engaging it. You can measure it using an adapter fitting plugged into SCV.
 
(quoted from post at 15:22:23 10/27/14) Thanks again for your support. From your experience is there
any way to prove that it is the clutch? Or at least a good
possibility as a tractor split is a major & then to find it was not
the prob. Just a thought. Cheers Grim
Click to expand...

Yes find out what the hydraulic pressure is supposed to be, then take readings and see what you get with the PTO disengaged and then when engaging it. You can measure it using an adapter fitting plugged into SCV.
 
Hi, I have found some info on the clutch and the pressure test etc. As you advised I will check that first. I have a feeling your initial response re the "cooked" clutch is probably right. Any air in the line would reduce the pressure and allow the clutch to slip. In hindsight I should have flicked the PTO off immediately. We live and learn. Thanks very much for your assistance.
 
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