I have a question about the 19mm coolant drain plug on the side of the M103 block. It appears that it's possible to attach a hose to this plug. Can someone explain how this plug works before I get around to flushing the cooling system?

TIA,
Bud

I suppose you should turn it until it begins to leak, then put a hose on it.

I had to use a 19mm deep socket with a pipe on the end. I just let it leak out on the ground. As I put a pint of water pump lube/ antifreeze restorer in mine on a yarly basis, the fluid was entirely clear, rust free and clean-looking after three years.


You will need to really tighten it. Mine leaked a bit after the engine heated up a bit. I'd start the engine with the car still on a jackstand, and make sure it was not leaking.

Hope this helps.

There is a place where you can put a tube on the radiator drain as well.

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1990 300D 2.5 Turbo sedan 171K (Rudolf)
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Thanks Richard,
I've been draining as much as I can get out by putting a modified clothes washer hose on the spigot at the bottom of the radiator but I was thinking of flushing the system and so I need to get it all out.

I've been refreshing as much coolant as I can out on a yearly basis so I may not really need to do anything more unless I start to have problems.

I have to drain the system in my garage so that's why I was asking about the19mm drain plug.

Bud

I put the front of my car up slightly on jack stands and caught the coolant in my 2 gal car wash bucket. I didn't attach anything to the plug and I barely spilled any. I used a 1/2 inch drive ratchet, medium extension and a short 19mm. It fit perfectly. Draining the block is simple and worth the trouble.

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D.H.

04 ML500
02 E430

Experience is something you don't get until just after you need it.