Anybody run into a issue with the thermostat on a m274 that will idle and regulate temperature ok but when driving it rises to around 105C and drops to around 85C, heats back up and does it again, by the 3rd or 4th time of it doing this, the temperature drops to around 45C and I my interior heat fades to cool as well? I have replaced the thermostat, waterpump, coolant temp sensor and radiator with no change. I wven changed the thermostat twice with mercedes parts.
It certainly sounds like a stat issue. Did you save the last one to tear apart and look-c if it was really bad?
There's also an elect plug on the housing, which I assume is the heating element to force the stat open. If it's powered on and stays on the temp can drop drastically. I'd be especially wary of that since it seems very unlikely you'd have a string of bad stats.
I assume it's cold where you are to hit 45C. With my stat wide open I remember it getting to maybe 60C, but I live in the desert. The only way for it to get that cool is the stat, forced open or broke and open.
If I unplug the little heater on mine it hovers ~100-102C. This heater is to open the stat to lower eng temp further, as the ecu sees fit. So you can simply unplug the heater and see if functions like a normal 100C stat. If so, then it's the ecu being stupid. If not, then I'd open that stat up to see wth is going on.
I got tired of the way my ecu dictates temp so I control the heater manually to maintain a much lower temp, and optionally I can flick a switch to open the stat all the way and keep it there. I think my fix is awesome, but if your ecu is screwing things up it might be a fix. It's easy and I can explain if you go that route.
There's also an elect plug on the housing, which I assume is the heating element to force the stat open. If it's powered on and stays on the temp can drop drastically. I'd be especially wary of that since it seems very unlikely you'd have a string of bad stats.
I assume it's cold where you are to hit 45C. With my stat wide open I remember it getting to maybe 60C, but I live in the desert. The only way for it to get that cool is the stat, forced open or broke and open.
If I unplug the little heater on mine it hovers ~100-102C. This heater is to open the stat to lower eng temp further, as the ecu sees fit. So you can simply unplug the heater and see if functions like a normal 100C stat. If so, then it's the ecu being stupid. If not, then I'd open that stat up to see wth is going on.
I got tired of the way my ecu dictates temp so I control the heater manually to maintain a much lower temp, and optionally I can flick a switch to open the stat all the way and keep it there. I think my fix is awesome, but if your ecu is screwing things up it might be a fix. It's easy and I can explain if you go that route.
