MF 390 engine oil level rising

[Marmite Mac]

The engine oil level on my 1995 MF 390 18-6 Speedshift seems to be creeping up! This is while the tractor is just standing in the shed. It hasn't been used much since an oil and filter change on 7th June (to set a correct oil level) but the level has steadily crept up by about 6 or 7mm in 4 weeks, always measured whilst parked in the same level place and mostly just stood there with no stored pressure in the loader hydraulics etc. Anyone come across this before?

 

[Zebbedee]

take drain plug out of sump and check for water, if not water probably diesel ( smell it diesel is quite distinct) check that first

 

[manhill]

The engine oil level on my 1995 MF 390 18-6 Speedshift seems to be creeping up! This is while the tractor is just standing in the shed. It hasn't been used much since an oil and filter change on 7th June (to set a correct oil level) but the level has steadily crept up by about 6 or 7mm in 4 weeks, always measured whilst parked in the same level place and mostly just stood there with no stored pressure in the loader hydraulics etc. Anyone come across this before?

Yep, oil seal in the Cav pump cured mine (2 off, one facing inward, one outward). Easy to replace, at least mine were.

 

[agrimax]

Or the lift pump leaking in,or the engine mounted hydraulic pump seal gone and transmission oil leaking in...

 

[ACEngineering]

Check the thermostart plug. Common to leak and wash fuel down the bores.

 

[manhill]

Yep, oil seal in the Cav pump cured mine (2 off, one facing inward, one outward). Easy to replace, at least mine were.

With the pump removed and connected to the lift pump, and operating the lift pump by hand the leaking seals showed up.

 

[Marmite Mac]

Thanks All, for the replies and ideas.
Have now checked the oil for signs of water or diesel. Not a sniff. Seems to be pure oil. No sniff of diesel at all. Drained some from the bottom (through the drain plug) and also checked through the dip tube. So the fuel pump causes seem less likely.
Turning to the hydraulic pump, there is no pressure in the hydraulics, and very little oil at a higher level than the pump (just the loader rams), that could cause leakage through gravity alone?? Baffling that something is leaking from somewhere, very slowly, into the engine oil when the tractor is sat idle.
Any other ideas?

 

[agrimax]

The steering orbital unit and associated hydraulic hoses/pipes will be higher than the pump,and likewise the spool valve blocks. Could still be the pump seal. What about the backend oil level on the dipstick? Has it dropped?
Raising the oil level by just 6-7mm with diesel dilution won't necessarily be noticed by a smell of fuel in the oil either. Could still be the lift pump,inj pump of glow plug.

 

[manhill]

How would hydraulic oil find its way into engine oil? I'm baffled.
If diesel is getting in, the engine oil will start to get thinner.

 

[Pistonbroke]

Not familiar with mf but a db1390 was doing the same here once and it was the power steering pump seals leaking oil back into the engine. Probably a different setup though

 

[Marmite Mac]

Thanks All, for your time and thoughts on this. Good point about the spools, orbitrol unit, etc. being higher than the auxilliary pump (generally believed to be the most likely potential leakage point, into the engine timing gearcase). It's tricky to see if the back end oil has dropped because it's so much larger a volume and any change in level is much smaller and the back end dipstick is difficult to read to that sort of accuracy. Also since the tractor hasn't been run (between recent measurements) any loss of oil from the hydraulics hasn't (yet) been replaced by oil from the back end, to drop the level.
Additionally, when I did do some heavy loader work between measurements (before the current "leave it standing" experiment) and hence creating significant hydraulic oil pressure in the auxilliary pump, the engine oil level didn't seem to change significantly before vs after, suggesting that the hydraulics may well not be the source of the extra fluid. So I wonder if it is indeed a bit of diesel leakage? Which were the seals that you changed on the Cav pump?

 

[agrimax]

How would hydraulic oil find its way into engine oil? I'm baffled.
If diesel is getting in, the engine oil will start to get thinner.

It won't be noticeably thinner to only raise the level by 6-7mm.
If the engine mounted tandem pump end seal fails,transmission oil will enter the engine oil.

 

[manhill]

Thanks All, for your time and thoughts on this. Good point about the spools, orbitrol unit, etc. being higher than the auxilliary pump (generally believed to be the most likely potential leakage point, into the engine timing gearcase). It's tricky to see if the back end oil has dropped because it's so much larger a volume and any change in level is much smaller and the back end dipstick is difficult to read to that sort of accuracy. Also since the tractor hasn't been run (between recent measurements) any loss of oil from the hydraulics hasn't (yet) been replaced by oil from the back end, to drop the level.
Additionally, when I did do some heavy loader work between measurements (before the current "leave it standing" experiment) and hence creating significant hydraulic oil pressure in the auxilliary pump, the engine oil level didn't seem to change significantly before vs after, suggesting that the hydraulics may well not be the source of the extra fluid. So I wonder if it is indeed a bit of diesel leakage? Which were the seals that you changed on the Cav pump?

two internal seals on the injection pump driveshaft. Verify that these are leaking by removing the pump so you can see the drive shaft and connect or leave connected to the lift pump then operate the lift manually. Give it a lot of strokes to make sure you've plenty of pressure. If you don't play with the timing the pump should just go back in its previous position. You could scratch marks on the pump and engine to make sure. I think new seals were about a fiver each if you see a leak.

 

[Friesianfan]

I had this problem on my 398. Back end oil was getting into the engine.

 

[Ffermer Bach]

Zetor had power steering oil leaking into the engine through the seals in the power steering pump

 

[Enry]

Had a fiat where back end oil was dropping and engine oil rising - seal blamed so tractor split, bell housing bone dry…turned out to be hydraulic oil pump seal…that was cheap, quick and easy…..of course we had split it first

 

[fermerboy]

How would hydraulic oil find its way into engine oil? I'm baffled.
If diesel is getting in, the engine oil will start to get thinner.

Not an MF but my 7840 NH dumped a lot of backend oil into the engine through the engine mounted pump which failed. It was throwing oil out the dipstick, breather, everywhere.
Took near 10 gallons out of the engine sump.
New pump, problem solved, old one had just on 16k hrs so didnt atempt a repair, though it had blown the shaft seal.

 

[Marmite Mac]

Having just done a hard working week of the hay routine the 390 oil level hasn't changed significantly! So I am monitoring it but pausing the investigations for now - either it has settled down by itself or I have been reacting to spurious readings of the levels. Thanks all for the input thus far.