factory engine block heaters.

[wd]

 I was wondering if Mercedes offered an engine block/oil heater as an option. 

[ja17]

Hello,

I have one of those octagonal sheet metal side covers for a M130 engine which has a fitting built into it for a standard Mercedes block heater. To install it you simply unscrewed the blank original cover and screwed on the cover with fitting. Then you could screw in the standard Mercedes Diesel block heater.

So I suspect that it was an option. If I can find it I will post a picture.

[wd]

That would be great to see a picture.

 I was busy learning about so many things after getting the car and forgot about the coiled ac line under the front passenger side bumper until the cold spell hit here in Seattle.  Started to plug it in then thought, better not. I looked through several service books and on-line but couldn't find any mention about block heaters. Need to lift her up and trace the line but looking from above the ac line seems to split and run to two bolts on the oil pan then from only one bolt a line runs up under the intake and must go to the plate you mention. I am guessing
 the oil pan bolts are stress relief/anchoring for the line.

[mnahon]

I came across the block heater on my (Euro) car today. It starts from a standard Euro AC plug under the front bumper and the wire then makes its way along the bottom of the right side of the engine, and then toward the rear of the engine, it goes upward to just below the exhaust header and attaches to the side of the engine where the block heater is presumably located. Since I don't plan on ever driving my car in cold weather, I'd be tempted to remove it; but the attachment at the engine would be pretty hard to get at and I'd have to find a blanking plate. So my 'if it ain't broke, don't fix it' instincts came into play.

This ebay listing that includes an options list for 280SL mentions a block heater on the second page, so I'm guessing this was an original option
http://www.ebay.com/itm/Mercedes-OPTIONS-ACCESSORIES-LIST-SL-W113-230SL-250SL-280SL-ROADSTER-Rdsr-COUPE-/330783328985