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1977 450SL
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I took my Auxiliary Air Valve off today and cleaned the inside with break cleaner and compressed air, my Question is after I boiled some water and put the copper end in the cup, the valve closed all but about a 1/16 of an inch. Does anyone know if this is correct, or should the valve close completely?

Thanks
 

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'72 350SL, '85 300D, '98 E320, '19 Subaru Outback (sold '14 GLK250)
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I took my Auxiliary Air Valve off today and cleaned the inside with break cleaner and compressed air, my Question is after I boiled some water and put the copper end in the cup, the valve closed all but about a 1/16 of an inch. Does anyone know if this is correct, or should the valve close completely?

Thanks
I believe the valve should shut completely. But at what temperature?

On the earlier D-Jets I have read that it should be 100% closed at 140F and in another reference at 150F. At max operating temperare, coolant is at about 185F on D-jet, so AAV is fully closed. Operating temperature on K-jet is higher, so perhaps the 100% closed temp is also higher? Maybe someone has a reference. But as a wild guess, it should be closed well below 212F.

Some say that AAV is always slightly open because of a step cut in the piston, but my guess is that is just for better flow and/or noise control.

To check if AAV is closing, pinch the hose off when engine is fully warmed up and see if that affects engine speed. It should not.
 

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Registered
1977 450SL
Joined
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50 Posts
Discussion Starter #3
I believe the valve should shut completely. But at what temperature?

On the earlier D-Jets I have read that it should be 100% closed at 140F and in another reference at 150F. At max operating temperare, coolant is at about 185F on D-jet, so AAV is fully closed. Operating temperature on K-jet is higher, so perhaps the 100% closed temp is also higher? Maybe someone has a reference. But as a wild guess, it should be closed well below 212F.

Some say that AAV is always slightly open because of a step cut in the piston, but my guess is that is just for better flow and/or noise control.

To check if AAV is closing, pinch the hose off when engine is fully warmed up and see if that affects engine speed. It should not.
Thank-you.
 
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