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1997 E420 Black Opal 1990 300e Brownish
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35 Posts
Discussion Starter #1
What is the fan called that is behind the radiator? It's not the aux fans behind the grille. This fan is staying on all the time. As soon as I start the car it is going full blast. Is it supposed to do that? I'm sure this has been covered but I'm unsure of what I should seach for. Thanks for your help.
 

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1989 Mercedes-Benz 300E
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23 Posts
Thats your main engine fan. If you lose that trust me you'll know lol. Nothing will work it's driven by your belt/engine. The one in front of your radiator is your AUX its electric and helps cool the engine by dragging extra air to your radiator also spins air toward your intake. That comes on at a certain temp. Theres a way to test that and its common if its not working at all. Not really needed tho, but nice to have.
 

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1997 E420 Black Opal 1990 300e Brownish
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35 Posts
Discussion Starter #4
Ok good, so there is nothing wrong. I haven't had this car that long and I'm still trying to learn all the in's and out's. Thanks guys.
 

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Premium Member
About a dozen 1988, 1989, 1990, and 1991 sedans, wagons, 4Matics and 1 coupe
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5,466 Posts
Engine cooling fan.

When you first start the engine the fan will turn at pulley speed (pretty fast) until the silicone fluid in the clutch get flung to the outside of the clutch housing. This may take a minute or so but not longer. You may notice fan roar at this time.
When the fluid has migrated the fan speed will drop noticeably and fan roar will disappear. This will be the case until the engine gets hot enough for radiator temp to act on the clutch bimetal element and close a valve inside the clutch. Now the silicone fluid is forced back into the clutch working area and the fan speeds up again. During driving where the car is almost always moving the fan may not come up to working speed again. That's normal. Sitting in traffic, however, you may hear fan roar come and go as you inch forward. Again, that's normal and proof that the fan clutch is engaging/disengaging.
 
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