Coolant Leak 1990 300E
 

I discovered today a coolant leak at the right side of the block below cylinder number 6. It is difficult to tell exactly where as the PCV pipe twists in there.

There does not appear to be any coolant in the oil or visa versa. Is there something that I am not seeing; I see a frost plug but not enough of it to determine whether that is where the leak eminates from.

Could this be the head gasket leaking coolant out?

It could be the head gasket, are you experiencing a rough running engine and/or misfiring?

Try inspecting the heater hoses that go to the back of the cylinder head.

Yep, on a 103 engine, that's one of the favorite places for the head gasket to leak. The coolant can come out, instead of going into the oil passage; that's the good news. Upon pulling the head, you'll see where the gasket was just scrubbed down by the constant expanding/contracting of the aluminum head on the iron block. About 100k miles is the usual life, according to the guys herein.

But, try to clean it up and be sure the freeze plug just below the head, or even the drain spigot, is not the culprit.

DG

It can also be the o-ring on the lifting hook on the drivers side of the engine as well.

MBDOC...I had the heater hose crack and blow on my '91 300E right by that engine hook where it goes into the block. Now, I get white smoke in the morning out of my tailpipe and a water drip (doesn't smell, taste, or look like coolant) for 5-7 minutes. Could the heater hose and steaming coolant have caused anything to loosen up or leak down there? No puddles are ever under my car. Slow coolant loss is now apparent.

Coolant Leak
 

As it turned out, the leak is coming from the coolant hose area at the back of the head and riding along the head gasket edge to the side of the engine where I spoted it. It is illusive enough depending on the angle the car is parked as was the case.

I understand that there is a gasket behind the hoses at the head that needs to be replaced. This appeared to be a common problem and created quite a puddle when the weather gets colder.

Anyone have any simple instructions on replacement?

Cheers,
W