Anyone familiar with block heaters?
 

My car came with a big 110v AC plug behind the grill and today I figured I'd plug it in. I had always thought that block heaters were just electric blanket deals so I was surprised that mine made noise. It sounded like an electric motor running. The wire just goes into a big plug screwed into the block behind/under the turbo. It was puling some current because the cord was warm after a few minutes.

So how do these things work?

Normally just a heating element similar to what you would find in an electric kettel. Plug it in and it gets hot. After 30+ years it may have corroded (most are copper) or have large deposits on it causing the noise and excessive current draw.

Or it could be operating normally. I've had ones I could hear and the cord does get warm since it's drawing current through it.

yours could be an aftermarket one. some are in the heater hoses, with pumps to circulate the coolant.
but like mentioned, you are likely just hearing the water boiling off the elements.

The standard MB Block heatyer is just a little heating element that heats the coolant in the water jacket. fits into the side of the engine on the right side in front of the starter.

http://img.eautopartscatalog.com/liv...1619895OES.JPG
this is one shown in Fast Lane.

Charlie

I just had an OEM block heater installed and it works great! Little expensive, but definitely worth it in a cold climate like mine.

As the others have said, check for corrosion since all the fittings are at least a quarter of a century old. A bunch of parts on mine were corroded so I had everything replaced.

My blockheaters have always made a little sizzling noise from the coolant being in contact with the heater element.

The noise is analogous to a kettle "singing" when it's on the stove. Has to do with tiny water bubbles forming and breaking, I think. Click and Clack would know.

The block heater should take about 4 hours from stone cold to easy-start warm. You'll also have heat in the cabin almost immediately. If you don't want to leave the block heater on all night (it draws a good 400 Watts and the aftermarket ones even more) you can set up a timer to turn on the block heater 4 hours before you need the car to start.

Jeremy

Be sure that your extension cord is an appropriate gauge for a block heater. They do draw a lot of current and the longer the run of cord the bigger gauge wire it should be. If the gauge is too small it could be the reason the cord is getting hot.

Thanks for the pic Charlie!! I'm thinking about adding one to my 240d.

They are nice to have on those cold mornings. I have a lower radiator hose heater in my 240, it was free and convenient. It helps but it's not as good as a real block heater. Also getting the freeze plugs out of the block and be REALLY hard, so a lower radiator hose heater is easier to install.

The PO of my car installed a small battery trickle charger and wired it to the same cord as the block heater, so plugging the car in both preheats the engine and tops off the battery. I thought that was pretty clever.

That's a pretty damned good idea actually.

Quite clever.
Is there any downside to trickle charging a battery constantly?

I think it would depend on the rate of charge. I mean people put battery tenders on their motorcycles all winter to save the battery's so it cant be bad for them.