Drain Point Blocked - Cooling Water

[dawntreader]

The drain point for the cooling system [see attached] on the starboard side of my D1-30 engine block appears blocked - the port side is ok. Even fully removed little water comes out. The user manual suggests there should be 4 litres in the system but I can only get 2 litres out  Anyone else had an issue with this and resolved it?

[Symphony]

Expect you will need to poke around the hole to clear any deposits. The drain is at the bottom of the waterway so that is where muck collects.

[Salty]

........................The drain is at the bottom of the waterway so that is where muck collects.

Logic, and as Symphony suggests, the bottom of the waterway is where all the "muck" would collect, but it can be surprising just how much of the stuff will be found on any horizontal surface in other areas within the cooling system. Around the tube nest within the heat exchanger is a favourite place, and this winter I have just cleaned out the cooling water expansion tank, removing a large quantity of sediment and enabling me now to see the water level within that tank once again. Oh, and by the way, this was the highest point within the waterway, where that tank was located some 30 - 40 cm above the top of the engine, and if that doesn't defy logic, then I don't know what does !!
One of my reasons, by the way, for taking that tank off was that directly below it, on my B36(2002) and in way of one of the cooling hoses there is a piece of electronic/electrical equipment located. This is something to do with the battery charging system, and has cooling fins that the hose was rubbing and chafing against. The tank when put back and after cleaning it, was moved 15cm to starboard to prevent further chafe on the hose. The edges, and particularly the corners, of those cooling fins are remarkably sharp.

[dawntreader]

Thanks Salty. I suspected a 'blockage' but what you describe seems to be much more than that and a full flush looks to be the order of the day. Incidentally, the service manual suggests replacing the tube nest - I take it you didn't consider that necessary 

[Salty]

So far as I'm aware, I haven't got a blockage in my MD2020D cooling system, and apart from taking the tube nest out and washing out any sediment between the tubes, the tube nest has not been renewed. I must take another look at the manual, as I'd not noticed any suggestion within it for tube nest renewal. Having said that it was only very recently that I saw the requirement for the fresh water cooling part of the system to be changed at least every other year. I changed it soon after buying the boat in 2010, but this Autumn is the first time it's been changed since then, and the water that drained out appeared very clean. So I guess the sediment must be internal corrosion.

[dawntreader]

I've had another look at the operator's manual and cannot find the 'discard' information for the pipe nest so that may be mis-information on my part 

Updated:
'Scrap info' is on Page 94 of this document: volvo_penta_workshop_manual_part_b   

[Eye Candy]

The manual says "scrap it".  I think it means scrape it - in other words clean it.  There is no mention of renewing it or replacing it.  The following step in the manual is to "Instal new O-rings on the insert". 
Cheers
Andrew

[Salty]

I agree with Andrew, though the wording at that point in the manual is uncharacteristicaly poor and confusing. It would have been much better if the manual had been more specific in regard to what each item was called, namely if it was the old "O" ring that was to be scrapped, then to call it an "O" ring instead of an insert.