Any tips on replacing the thermastat on a 99 E300? I can't find a service manual and this is the first time. Can it be done with alternator in place? Secret to getting to the bottom fastener? I'm sure it will reveal itself as I go. Any info would be great.

One tip I can give is about bleeding system after filling.
Obviously set heater controls to full hot … once system is filled get the engine started and then loosen the clamp on the highest pipe fitted to the duo valve …push the clamp off the pipe , loosen the pipe on the stub and push it nearly off the pipe and then use a thin flat blade screwdriver just gently lift the hose up to let air out of the system …. Leaving the hose on the stub of the pipe this way releases air in system but ensures the pipe is easy to refit .

Thanks

The 606 has a coolant bleed bolt. It is just aft of the upper radiator hose where it attaches to the head. It is a large hex head bolt. Loosen or remove it and fill the antifreeze mix into the overflow tank until coolant comes out the bleed hole. Then install the bleed bolt and continue filling to the fill mark that can be seen through the fill hole.

PS I recall that I had to turn the thermostat in the housing until it dropped into place. There was some sort of locating pin in the housing of my '97 that only allowed the thermostat to fit in one orientation. I am not sure that applies to your model.

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'97 E 300 D