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Outstanding Contributor, Vintage Moderator
450slc5.0cab 280sl5sp 280se4.5 500se+500slAMG +250seStkW108 350sl4spdX3 500secEuro
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@cushjbc and @MBGraham are the most active and knowledgeable users I know. I believe the wax filled bulb is crimped to make it open through the right range of temperatures. It (like a thermostat) does not “pop” open but slowly opens through a range of temperatures and is probably fully open at one temp, and fully closed at another, but I don’t know either temp.

Edit, oops, I was thinking of a 107, but I bet the concept is the same, having a range of temps.
 

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'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
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@cushjbc and @MBGraham are the most active and knowledgeable users I know. I believe the wax filled bulb is crimped to make it open through the right range of temperatures. It (like a thermostat) does not “pop” open but slowly opens through a range of temperatures and is probably fully open at one temp, and fully closed at another, but I don’t know either temp.

Edit, oops, I was thinking of a 107, but I bet the concept is the same, having a range of temps.
You are right Fonzi. The fluid in a bulb like that will expand gradually when heated. On an AAV, that would gradually move the piston to close the valve. On status, it would gradually move a disc to open or close the coolant. At just what temperature, would be part of the mechanical design an likely wouldn't help in applying it to an AAV. The bulb likely moves the push rod the same amount in both cases for he same temperature change. ÌBoth are immersed in the same coolant and close their valves at about the same temperatures.
 

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You are right Fonzi. The fluid in a bulb like that will expand gradually when heated. On an AAV, that would gradually move the piston to close the valve. On status, it would gradually move a disc to open or close the coolant. At just what temperature would be part of the mechanical design and likely wouldn't help in applying it to an AAV. The bulb likely moves the push rod the same amount in both cases for the same temperature change. Both are immersed in the same coolant and closes their valves at about the same temperatures.
I think that would likely be a wax-filled thermostat. There is a temperature range on that part but the main thing is that the sliding air valve is completely closed at full operating temperature.
 
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