[samcast]

Hello, I have a 1979 450SEL, runs great until I shut it off.

Turning it back on takes at times it takes 10 seconds and then the idling is very low.

After checking a few my mechanic said that it probably was the Water Temp Sensor and he would order the part. Somehow that doesn't sound right. Any other things to check.[V]

 

[mercmad]

There are lots of things to check,I would book the car into an approved Bosch fuel injection specialist in your area.They will check things like fuel pressure,fuel volume,all the sensor workings and the fuel distributor with it's ancilliaries such as the acumulator and cold start actuator....etc etc []
Letting your mechanic just change things until it runs right is a recipe for an empty wallet and a feeling of disrespect for your mechanic ,something best to avoid.