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The saga continues. I swapped in a new thermostat tonight. Now it holds temp perfectly.
But... After allowing it to heat up and evidence the ability to hold temps now, I found a new leak that I had not seen before. Now it is below the thermostat at the front of the engine. My guess is that the water pump is down in there somewhere. Could there be any other source of a coolant leak amongst the pulleys?
If you look at this picture, the leak is a steady stream that looks like a string next to the second belt.
Now I have to wonder what a water pump costs. Tempted to get a quote for the work too, since I have other car projects I want to wrap before it gets too cold.
Hi, I might have the same problem as you. I think I identified my leaking spot as the lower coolant hose where it connects to the water pump just beneath the water pump pulley. I'm quite certain that that is also your issue.
When under the car, looking between the subframe and the oil pan, you can see the top of the lower coolant hose. It is a huge pain to get the hose to fit there properly. I tried twice and still didn't succeed.
I took some pictures as well but couldn't take a good one:
Red arrow points to the suspected end of the lower coolant hose connecting to the water pump.
Blue arrows show from where the coolant drips down.
View from the front w/o underbody panels.
As said before, I tried to fix it twice and couldn't do it. The main problem seems to be the engine facing part of the hose which is hardly reached. I have a hard time pushing the hose up the whole way.
It also might drip down from the water pump above it. Didn't see proof for that yet, though.
Brought my car to a mechanic who said that it's most probably a leaking waterpump.
Can someone confirm that the replacement part 'Optimal AQ-2311' is a decent substitute? Wouldn't want to go through that hassle twice.
I'm looking at 120 EUR for the Optimal replacement compared to somewhat short of 400 EUR for the Benz branded one.
Most probably? That doesn't sound convincing to me.
You don't want to go around this car and replace parts you don't need! See if you can get under the car and get to the spot the other poster pointed out.
I'm on looking for head unit upgrade options for Bluetooth, but thought I'd update here.
The water pump had begun to go and the lower hose had also begun to leak. That was the bottom source of the leak. I replaced the entire coolant system, essentially, for just under $1,000. Radiator, thermostat, water pump, intercooler pump, upper/lower rad hoses, and thermostat hose. The stays rock solid temps now. I do need to go back and add the expansion tank mod for the IC piping. I have the parts, just need the time. I was focused on the weekend car and the SC install/tune. Now that the temps have dropped and that one's giant meats are slipping on cool pavement it's time to focus on the winter beater (S600! lol)
I also ended up replacing the lower hose and the water pump. For me the water pump replacement did the trick. Thank god, no more leaks! I'm wondering if the water pump gasket ($7) would have been enough. With the pain in order to get to the pump, I wasn't feeling like trying and probably doing it again in the end. So the conclusion might be: if your car leaks coolant below the pump and you checked the lower hose --> it's probably the pump.
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