Unimog oil leak (expert advice required!)

[David Riding]

When I bought my Unimog the Clutch was slipping hence got it cheaper. However I did not take the plug out of the bell housing when checking the vehicle before purchase and loads of oil came out. Turned out crank seal had gone and contaminated clutch. Crank seal had gone because shells were worn. Anyway got it all sorted was not that more expensive that just doing the clutch. I now have a small amount of what looks to be gear oil coming out of the bell housing obviously another seal, my question is this: should this have been picked up on when the mechanic was replacing crank seal, shells etc.

[Dean Lofthouse]

It's more or less impossible to pick up a fault like that with so much contamination and oil about.

 

When the bell housing came off it will have been smothered in oil which will have then been power washed off, you can't check for play in the gearbox input shaft because there is always a little there.

 

The only way would to have been fit it and run it a while.

 

As a little tip, unless you do a lot of deep water or deep mud wading, leave out the gearbox plug, that way you pick up these faults quickly because you'll leave an oil drip everywhere it's been parked.

 

I know you bought it like that but in future at least you'll be able to plan the work.

 

I've just changed the engine on my landy because of the rear engine oil seal. But I've known about it for 10 months, sourced a new engine and planned the fitting. The clutch was brand new 5k ago and was still bone dry

[b101uk]

The simple answer is yes & no, though as Dean says with the latter that the amount of oil about would make it hard to see ware a small leak was when there was a much worse leak in the same vicinity.

 

However most mechanics would place the PTO Gearbox (assuming an MBU/SBU) with the bell housing/input-shaft pointing down on e.g. a wheel to allow any oil to show its self by leaking past the seals from a high head of oil just like any gearbox.

 

what unimog is it?

 

if a MBU/SBU unimog also check that the output flange on the PTO box that the prop-shaft to the main gearbox fixes to has no play in it, if the output flange has play in it then the centre retaining bolt that holds the flange onto the output-shaft will be lose witch in turn will not preload the bearings which helps centre the input shafts that the respective clutches work on.

 

Out of interest is your clutch a single plate 540/1000rpm PTO or twin-plate 540/1000rpm PTO?

[David Riding]

what unimog is it?

Out of interest is your clutch a single plate 540/1000rpm PTO or twin-plate 540/1000rpm PTO?

 

It is a U1000 and is dual clutch is that the same as twin-plate?

[b101uk]

Do you know that the twin-plate/dual clutch requires setting up with the right pre-load on the respective half’s of the clutches vs. the flywheel so the clutch release bearings have the correct hight throw to disengage the relevant clutch without dragging or to allow the relevant clutch to engage fully without slipping, also the PTO clutch release air cylinder requires to be set up so the patruding pushrod sticks out a precise distance vs. the mounting surface on the bell housing & the depth of the ball-socket on the release fork that the pushrod engages in.

 

The twin plate clutch like any/most types/makes cannot just be put in like a normal single plate clutch or it stands a high chance of not working correctly under high power especially the PTO clutch.

 

Secondly you say “I now have a small amount of what looks to be gear oil coming out of the bell housing” have you established this by its smell like EP/EP Hypoid gear oil? If so your PTO should not have EP/EP Hypoid gear oil in it ! It should have straight SAE 80 GL4 gear oil in like your main gearbox.