104 coolant drain plug removal
 

Does the coolant drain plug on a 104 come all the way out? The service info says just to loosen a turn or two to drain the block. I think I have crud build up that is preventing the coolant from flowing. The plug turns in the open/out direction easily for 3 or 4 turns then it gets very difficult to turn. The online epc references a leak repair plug that goes in the outside of the existing plug. This makes me wonder if the plug is intended to come all the way out? Anybody know the answer. (engine is 104.992)

Thanks.

J. M. van Swaay

Since it has a nipple, it is not designed to come out. I would say the problem is that you have a vacuum that is not allowing the coolant to drain out. That's why there is a vent bolt on the top of the engine. On the M103 it's on the intake side just back from the front of the engine. Not sure where it is on the M104, but it's there somewhere.

Steve

Think I mis-spoke. Think that is used to vent air when re-filling with coolant.

Steve

Loosening should allow the coolant to drain. It's a good idea to take it completely out occasionally to clean the treads and put a little anti-seize on them.
When I bought my 95 E320, the drain plug was very badly seized. Probably had never been opened to properly change the coolant even though it was serviced by the dealer since new.
I had to take the exhaust manifolds off to finally work it out. Plug was destroyed but luckily the block was OK.
If yours gets difficult to turn, be patient and work it back and forth until it can be removed.
You might need a good flush if you have that much crud in the block.

That side drain plug is just a hollow bolt with a tapered seat and it should unscrew all the way....however, i have has dozens of them not unscrew more than enough to drain the coolant rather than come all the way out.

If you insist on removing it then you need to apply some heat from a torch...and then wring it out with a short 19mm ring or deep throat socket.

If so...have a replacement handy.

Thanks for the replies. I have no doubt I can get it out--just did not want to break/ruin anything. Six point socket and big cheater bar, no problem.

Incidentally, this vehicle has been serviced according to the MB schedule by the dealer up to 160,000 miles. This drain plug appeared as though it had never been touched. Also, the transmission drain had never been removed either--black paint still around sides of plug head where it meets with the pan. Makes me wonder.....