Hi all - my R129 SL280 with M104 has been off the road too long! It started with a spray of steam from the engine bay that covered the external windscreen. I have discovered the water leak seems to be coming from a plug at the back of the head.



I have searched and searched and not found anything about this anywhere.


I *think* I have managed to attach two pics.

One is of the leak in my vehicle. Difficult to get a good pic.

The other is a screenshot from a video I found that made the location of the plug slightly clearer.



Has anyone had to replace this? Did the engine have to come out?

if it is, and not the coolant tee. Be good to just remove head and repair,and replace head gasket,which will blow next

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

If it is indeed leaking from that location the cylinder head or the engine will have to come out to repair it. It looks like it is a freeze plug that has probably rusted through from the inside out. Get an inspection mirror to get a better look at it. It's also likely that this isn't the only one rusting through.

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Mercedes Benz Master Tech - Retired

yep, pull the head. if you do, use the mb or elring head gasket. any other brand will have the typical 104 oil leaks in about 1 yr.

Thanks guys. I think you're right. Unfortunately I did the head gasket about 20k (6-8 years) ago and it's been fine. Oh well head gasket again it is! ;-)