Block heater install question
 

How do you get that massive plug out of the block? It looks like it takes the worlds largest allen wrench.

Yeah! And once you get the allen-wrench/socket, It takes a breaker-bar, with a length of pipe on the end to free it. The block-heater I installed several years ago on a '79 300D required removing the intake/exhaust manifolds for access. My neighbor, who works at a machine-shop, cut me a short section of allen-wrench stock, that I was able to stick in the plug and put a socket on.
Soak that plug in penetrating-oil too. Some have said it's possible to crack the block trying to get it out if it's really seized.

Happy Motoring, Mark

Put a lower radiator hose heater in instead. It's not worth the headache to try to get the plug out. As I recall, an 1 3/8" heater works. DieselGiant sells heater with the hose already attached or you can buy the heater and cut your hose. Takes half an hour to install with no risk of cracking the block or your knuckles.

Thought about instaling a hose-heater in one of my 240Ds, but so far both have started easily on the glow-plugs at temps down to about 25 degrees. Down to around 18 - 20, which is the coldest I've started one of these, it might take two or three tries before they stay running.

Happy Motoring, Mark

MB got it right when they decided to install them in every 603 engine sold here in the US. It was a easy task to install the power cord on the 20 year old, never been used block heater.

-Jim

I have installed a number of block heaters. That plug is really fossilized in place, and this was 20 years ago. I would be fearfull of breaking the block, as was already mentioned. I'd fit an in-hose heater.

It's a painful removal, however a strong impact wrench will get it out. An electric unit with 320ft-lbs was NOT able to get mine out, I had to use a friend with a 6' cheeter. A strong air powered impact wrench will put out more torque, and would probably get it out.

I found there wasn't enough room to use an impact wrench of sufficent power to remove the plug. My 3/4 drive wrench barely fit and was never able to loosen the plug. I used a 3/4" T-handle and a stubby 19mm hex key along with a 6' cheater pipe. And a pencil clinched between my teeth.

Yes, I failed to mention I had my engine on a stand when I replaced the plug with the heater.

Removing the manifolds, a 7/8 (I beleive) socket on a piece of allen stock, with a breaker-bar and 4 ft of pipe got it loose. Only recently found out about the risk of damaging the block, otherwise I might not have attempted it. I currently have a brand new flea-market in-hose heater but its a super-capacity unit designed for a big truck engine. Would probably get the coolant quickly boiling in my 240D!

Happy Motoring, Mark