leak from thermostat housing after water pump change

[ericzacha]

I just spent the weekend changing the water pump and tensioner on my '88 300 SEL, M103 engine. Unfortunately, I forgot to order the extra metal tube leading off of the water pump going to the heater core, so my car has sat for the last three days waiting for the part to arrive. Came today, and I ran outside to put it on. I was starting to flush out the system with water, when I noticed the thermostat housing was leaking . Still have the original plastic housing, but it has no cracks. I tightened the thermostat housing bolts to 10 Nm. I checked and the thermostat is facing the correct direction and the O ring is in place. Has anyone else had this problem before? I'm thinking I will just goop on some gasket sealant, but before I did that, I thought I would check to make sure there wasn't something else I wasn't thinking of. It is such a bummer to spend 8 hours replacing a water pump only to have more coolant leaking off the front driver side of the oil pan than before.

[Ferdman]

Eric, recommend that you replace the plastic thermostat housing with a metal one. The metal ones are relatively inexpensive. May not solve your leakage problem, but will eliminate future potential problems with the plastic thermostat housing.