Pressure test good, vacuum test... Not so good

[Scanman1973]

Hi All,

I had an issue with the shift mechanism on my DP-E drive. The marina "fixed" it, but when it was hauled for hurricane Irene oil was leaking out again. They "fixed" it again, and when I drained the oil at the end of the season it was apparent that water got back in the outdrive. I flushed it with fresh Volvo oil and pressure tested it and it tested fine. After a few weeks I noticed oil on top of the shift mechanism (I overfilled it for the winter accidentally, and was planning to fix the overfill before launching). I just drained and pressure tested it again, held fine.

Then the vacuum test would only make 13 inches of mercury of vacuum, and dropped to 11 quickly, under 2 minutes. I heard a popping around the shift mechanism. I pulled the shift mechanism and found a small piece of debris between the o-ring and the housing. I cleaned everything, put it back together and tested again. Same thing, holds pressure, but vacuum drops to 11 fast, but now there is no leak sound coming from the shift mechanism.

I am going to put a new o-ring in the next few days and try again. The manual says to use white sealing compound on the surface. Is this right, and what is the next step if the vacuum test does not improve?

Thank you,
Andy

 

[Scanman1973]

Re: Pressure test good, vacuum test... Not so good

One more thing I forgot to add. When I installed the shift mechanism the shift shoe was facing the wrong direction. I reinstalled it the right way and it shifts fine, but did I cause any unseen damage??
Thanks again,
Andy

 

[Scanman1973]

Re: Pressure test good, vacuum test... Not so good

--update:

I think the shift mechanism seal is OK now, and now I can hear the vacuum leak coming from the U-joint seal. I understand that this is a one way seal. It holds 11 in/hg, is this OK, since it will be sealed inside the bellows, or do I need to replace it?

Thank you,
Andy

 

[billbayliner]

Re: Pressure test good, vacuum test... Not so good

Hi Andy: Volvo pressure test and vacuum test procedure are in the Shop manual. It is in the Adults only section.

Is is actually nice to see a owner of the best drive ever made, that being a Volvo AQ series, doing a preventative maintenance on their drive.

Andy, I personally, and as Volvo requests in the manuals, use Mercruiser Perfect Seal, Volvo brand sealant or Permatex Aviation #3 on all seals. Please do not interpret this to mean using the sealant on the lip of seals but on the outer seals surface and also complete o-rings.

As far as I am concerned, all boaters should have this on hand and use it on all bolts for corrosion resistance and also I use it as a form of loctite if I am concerned about the bolt / nut backing off.

Never hardens and cleans right up with lacquer thinner.

 

[billbayliner]

Re: Pressure test good, vacuum test... Not so good

Was just thinking about this thread and something did cross my mind. On the eccentric piston, did you "polish the brass before installing in the mechanism?

Also this is a directional seal and will eventually fail if installed the wrong way because a tiny little portion of the metal will be exposed.

 

[Scanman1973]

Re: Pressure test good, vacuum test... Not so good

Thanks for the replies Bill, I will use sealant on the o ring when I get the new shift mechanism, looks like the pin bent a little when I attempted to reinstall the mechanism with the shoe in the wrong direction. Do I need to polish the eccentric piston on a new shift mechanism?
Thanks again,
Andy