Coolant Leak: But where's the source
 

I have a small coolant leak. See photo, green line shows where coolant collects. It's not leaking from the hose, no white traces of coolant at all. I do not have an adapter for my pressure tester to fit the 99 ML 320 reservior so that's out.

Do not know where the weep hole is but I would think it would be on the bottom of the pump, then maybe not.

Could it be leaking at the point where the gasket goes between the pump and the head?

Anyone have any experience with a leak in this area?


Edited:
Upon further review of the situation I'm thinking it's the thermostat sealing ring. I can not see that it's leaking from around the thermostat housing, however one of my other Mercedes leaked from the housing and I could only determine that as being the source of the leak after using my pressure tester when the vehicle was cold. That vehicle had an o-ring as the sealing ring; maybe the ML does too.

I replaced the thermostat sealing ring and now no leak, at least so far. I bought the pressure tester adapter and checked it when cold and it seems fine.

For those that might want to buy a pressure tester adapter to fit their Stant tester it's an FZ35A and it's made by Assenmacher.

Nice clean engine Ron! :sun_smile