How to drain coolant from 8.1S engine?

[Jimmy Buoy]

Had a leak in my Sbd Engine's heat exchanger that has now been repaired. The leak allowed coolant to leak out as well as lake water (fresh) to enter the block.

Time to drain remaining fluids and replace the 5yr Dex-Cool antifreeze.:thumbsup:

Anyone know how to access the block drains on the 8.1 engine. I can see the drain plug heads, but there's way too much "stuff" blocking any access with tools. Oil cooler and raw water hoses are on one side and raw water hoses on the other side blocking access. Taking hoses off that have been there for 7yrs is not a fun job, especially just to drain a block?:smt100

What am I missing here??:huh:

 

[Jimmy Buoy]

:smt009Nobody's drained their 8.1s coolant?:smt009

 

[Jimmy Buoy]

Now why didn't I think of that!?!:smt101

 

[Sublimetime]

pull the lower water pump hose. drain refill with fresh water drain again. fill with strong anti mix and check with tester. adjust as needed

 

[SeaHarley]

You might try removing your "knock" sensor in the side of the block.

 

[Jimmy Buoy]

Thanks for the suggestion. Hopefully there's not much more coolant below the lower hose.:thumbsup:

 

[SeaHarley]

The engine block holds a lot.

 

[Jimmy Buoy]

I've never noticed a "knock sensor" in my Merc Manuals. Time to take a closer look!

 

[Skuza]

Today while poking around the 7.4's I noticed a 1/2 or 5/8" hex plug on the bottom lt side of the blocks. This plug was not painted black like the rest of the block and appeared to have sealant on the threads. I wonder if this could be a drain for the coolant? It was about center of the side of the block and about an inch or so above the oil pan. Anyone confirm? I need to change the coolant this year also and would like to know.