Just ran across this thread and after my experience thought I should chime in. I already had a block heater installed, but it was bad (I thought). It tested open with a meter from the plug, but the cord was a little ragged, so I clipped it off close as I could from above and tested again and still open.

My water pump went out and it was fall, so first winter with the car was in mind and I figured I'd better go ahead put in a new one while the coolant was out. Found a local Benz guy that had one available.

VERY tough to get to being under the turbo and above the starter.

The heater obviously did not have the inside hex due to the connector on it but had a large outside hex. Borrowed a 3/4" socket set, but 1-3/4 didn't fit and 1-7/8 was too loose. OK it's metric, apparently 46mm. Where do I get one of those? Turns out 1-13/16 is VERY close but why would anything SAE actually need that size? 1/8 increments ought to do it one stuff that big. Fortunately this was not the case. Northern Tools had 1-13/16 and was happy to sell me one. Also a short extension as the thing is too far in over top of the starter, but not far enough for the longer extension in the set. But still have to use the breaker bar at a slight angle. Can't quite get right angle for the ratchet.

VERY challenging crawling under the car and getting it all in place and then setting up to torque on it. Have to turn the steering wheel to move the linkage somewhat out of the way. Lots of fiddling and frustration. Hard to set it all in there and hold it in place, let alone be able to apply torque. Have to brace the extension with a chunk of wood against something (turbo?) to stay in place.

You'd think a breaker bar for 3/4" would be plenty long (about 2 feet!) to bust it loose. I braced myself with my feet and gave it all I had with both hands. No go. What do I do now? No room under the car for a cheater bar (without digging a hole in the driveway). Finally hooked a small ratchet strap to the tow hook on the front bumper and to the end of the breaker bar. This finally made it move.

There was JUST enough room to get 1/12 of a turn. Release the ratchet strap. Everything falls out. Replace the socket, breaker bar, wood block again (a very fiddly process done mostly by feel). Hold it with one hand, try to hook up ratchet strap, but it falls out again, so several attempts needed. One more 1/12 of a turn. Repeat this process many times. Finally is loose enough I can turn it with a 1/2 ratchet (glad I got the 1/2 to 3/4 adapter at Northern also!).

That has got to be the toughest thing I've ever done on a car!

After all that, the heater tested good on the bench!!! Turns out the cord was bad right in the connector. The new one (Zerostart) had a different connector, so I could not have swapped just the cord anyhow.

But there ya have it. Use a 3/4" breaker bar (with short extension) and a ratchet strap!

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1985 300TD 214k. Elsbett VO system + Fattywagon injection line heaters. (SOLD!)
1996 VW Passat TDI wagon 327k. No VO
Two white german turbodiesel wagons. One analog, one digital.