D1-30 mixing elbow question...

[sheral]

There is a ‘drain tap’ on the mixing elbow (Volvo Penta - same style drain tap as on the block and the heat exchanger). However, there is nothing in the maintenance manual about when/how to use the drain tap on the mixing elbow.

Surely the drain tap is there in an effort to help keep the mixing elbow clean of build up/debris? When and how should it be used?

 

[REO6205]

Wow, fifty two views and not one reply. Not even a WAG. I have the same engine
Open that puppy up and see if anything comes out. Maybe hold a clear container under the valve to better see any particulate matter or contaminant.

 

[sheral]

I have put her to bed now, so will give it a try next season. Also drained/flushed the closed loop antifreeze out of it this year. (Fwiw: the antifreeze was clear and no scale or crud was in it at all. Flushing it with clean tap water also provided no crud. The boat only has about 180 hours on it. So other than for peace of mind, and maybe the antifreeze chemistry, seems 3 years / 180 hours may not warrant a drain and flush). That’s when I noticed the drain tap on the mixing elbow. I flush the open loop system with fresh water and use Salt Away at the end of each season, so hopefully that helps a bit. I know the mixing elbow is a wear item, but would like to keep it around as long as possible. 🙂

 

[Newf]

As noted on a previous post, I have 1340 hrs on the same engine so with you only having 180 hrs you should have a few good years left yet. I have never removed the mixing elbow for inspection and have had no signs of flow restriction. I have opened the little drain tap and I just get clean water so no plugging at this point. I have never flushed this system for storage purposes as I use the boat all year round, usually 2 to 3 time a week. As there has been a bit of discussion in posts recently on this item I'm thinking maybe I should take it off for a quick look. For those of you that have removed it, can you re-use the same gasket ? I should probably source out a gasket before I pull it, just in case..

 

[knotflying]

I am not familiar with the Volvo, but should you really flush out the closed loop with fresh water? On our Yanmar you can only drain out half of the coolant so I replace it every two years. So if one was to flush out the system with tap water you would be leaving half the closed system with water before adding the antifreeze. Additionally you are really supposed to use distilled water if you are using the straight antifreeze with a 50/50 mix. If you are using the prediluted and there is water left in the system then you may not be getting the strength you need. Hopefully the Volvo is different and this is not an issue, but I thought I would mention it.

 

[sheral]

Thanks gang. Yes the VP manual says to drain the closed loop antifreeze and flush the block / heat exchanger with fresh water (it says something to the effect of putting a garden hose into the appropriate fitting). I do mix my antifreeze 50/50 with distilled water and actually did get almost the full amount of old antifreeze out of the block / heat exchanger when I drained it so maybe it is different from the Yanmar system. ??? But I did suck the antifreeze and later the flushed water with an evacuator pump, so maybe that’s why. Regardless I am pretty confident I got all the water out.

 

[knotflying]

Good to know. I just didn't want you to have a false sense of security if your system did not empty all the way.

 

[sheral]

Copy thanks. The more I think about that drain tap on the mixing elbow the more I scratch my head. Correct me but the mixing elbow (never had one apart in my hands) likely has a center passage for exhaust gasses and an outer passage where raw water passes, right? If that’s the case, then why would there be a drain tap on the mixing elbow. Even if you flushed water through there, it would just pass out the exhaust outlet... hmmm.

 

[knotflying]

Your assumption is correct. On my Yanmar there are a few places with threaded plugs. I assume in the event you needed to add something. As an example there is a tap for a line that leads to the stuffing box. Not sure why there would be a drain on yours.