DPS-A Bad Seal Somewhere

[BRICH1260]

I pulled my lower unit as I do every year for winterization. This year I found my drive oil slightly white in color. It appears I may have a very slow leak somewhere. I have pressure tested the unit and it held 15 lbs for 24 hours. Vacuum tests show a slow loss over an hour or so. Which seals would be bad based on this information. Pressure good, vacuum bad.

The prop seals are original, 10 tears old. All other seals have been replaced over the last couple years.

 

[Scott Danforth]

actuate the shift linkage and turn the shafts while pressurized, however the prop seal would be my first guess. you lost an outward facing seal (water side) and when the gear box cools, it pulls water in past the oil seal.

 

[cptbill]

A few years back on my DPS-M out drives I had that problem it turned out to be shift shaft seal very easy to replace, not saying that's what yours is but that what mine was. While I was at it I also replaced the seals on the drive unit dip stick and the seals in the drain plug. If you can't find the actual source of the water entry that's where I would start

 

[QBhoy]

The drain and fill screw seals are nothing short of rubbish on these. Really common for this to happen this way here. Like literally every year someone will have water in their oil from a bad seal. Usually solved by silicone over the screw after an oil change.
pressure test acceptance is losing about 1 psi over a time I can’t remember or something.
but these drives usually sit about a metre under the surface with about 1.47 psi trying to get in.

 

[Lou C]

I change the fiber washers used on the drain/fill plugs every time I change the gear oil. Not sure if Volvo uses these or an o-ring?

 

[QBhoy]

I change the fiber washers used on the drain/fill plugs every time I change the gear oil. Not sure if Volvo uses these or an o-ring?

Yeah. They use a o ring usually. They are next to useless and especially if they are nipped or deformed when fitting. I actually used to use the merc fibre washer seals and also the oring, then silicone on top. Always sorted it out.

 

[Lou C]

If they use an o ring I bet the issue is people are over tightening them and causing them to deform. The OMC fiber washers do not deform.

 

[Thalasso]

Most likely when they put them on they are nicking them on the threads.Also if not using OEM the o-rings can be just a fraction thicker or thinner and won't seat right. Might look the same but they aren't

 

[BRICH1260]

Acknowledging the fraility of the O rings I usually try to put a good seal of VP grease on them and the screw when reinstalling the screws. Gonna replace the prop shaft seals this winter and hope that they were the cause of the leak.