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THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHDoes my engine compartment fan work?
Leading reported evidence
Run fan
Suggestion or failed attempt
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0
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1
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Suggestion
Probably a breakeven scenario - the only upside would be avoiding running the fan for long periods with the engine not running.
Leading evidence: 'Run fan' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Run fan' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suggestion
What you are hearing at cold startup is the air pump running for the first 1 - 2 minutes to warm up the cats.
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Suggestion · Original poster
The dealer told me the turbos run hotter and the fan is on way more often
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Suggestion
Maybe I'm missing something, but the fan always runs when the engine is running on the turbo.
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Suggestion
I was at a DE yesterday, 84/ hot, multiple long run sessions, 138mph, never came on.
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35 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
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Generation: 20261026T200546Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Got my car in October. Have not heard the engine compartment fan, ever. Didn't think it was an issue, even though we had a 90+ degree day last week.
Tonight, I was walking down Santana Row in San Jose on my way to dinner, and there was a 996 TT out front of the restaurant. I could clearly hear the fan blowing, and it was barely 70 degrees outside.
Thoughts?
My fan comes on when I start the car for the first time in the morning then quickly cuts out. I was told it comes on for emissions reasons. The fan stays turned off the rest of the day.
The fan should not come on when you start your car or at any other time your engine is running unless the heat in the engine compartment is above around 180 degrees F. What you are hearing at cold startup is the air pump running for the first 1 - 2 minutes to warm up the cats.
To test your lid fan, simply remove the 2 wire connector from the temperature sensor located between bank 2's intake tubes. With the key in the on position, the fan should immediately start and then turn off when you plug the connector back in.
They rarely come on, like '99 said the sensor is set at 185 degrees in the engine compartment. I was at a DE yesterday, 84/ hot, multiple long run sessions, 138mph, never came on.
I have always had a question about the fans and DEs. At some DEs, you see people all over opening their trunk lids, presumably to aid in cooling. However, doesn't opening the trunk lid prevent the fans from coming on? Wouldn't it be better for cooling purposes to have the fans than to have an open trunk lid? Based on this assumption (which could be incorrect), I have always left mine closed . . .
Yes, but with a closed lid and spoiler down, pitted car, you're really circulating a lot of hot air. I usually open mine.
BTW Todd, missed you at the glen yesterday, track was awsome, 138 on the back straight!
Just tap into the connection wire and put a switch in the cockpit. Then you can turn the fan on manually. It makes a big difference sucking cooler air into the engine compartment.
Come on Lee.... guys like you and I who should have been checking out hood temps at every light with the Rotary motors should be used to this.....
-Eli
Maybe I'm missing something, but the fan always runs when the engine is running on the turbo. When the engine is off, it only runs when the engine compartment is hot.
As far as opening the hatch after a DE session, the point of the fan is to keep the hot (mainly exhaust heat) air out of the engine compartment. Opening the hatch shuts the fan off (of course) and lets the heat pass over the engine and components, but escape out the hatch by convection. Probably a breakeven scenario - the only upside would be avoiding running the fan for long periods with the engine not running.
ah, i thought you meant it does double duty throught the same fan opening.
what you are saying makes sense. convection helps if the fan sucks the air out but apparently it does the opposite of what you are thinking.
Guys,
It is an exhasut fan, drawing hot air out of the engine comparment, 1999Porsche911 is incorrect in saying that it is drawing outside air in to the engine compartment, unless he got the polarity wrong.
For example, Manthey Racing has relocated the fan to the center of the lid on their GT3MR version and hooked it up to a manual switch. Some of their cars even sport dual exhasut fans!
I open up the lid on trackdays as I pull in to the pit, thinks it's more effective. If you don't want to bother opening the lid, leave the key in the ignition, turned to position 2 and the fan should come on.
Ciao,
Johannes E.
[QUOTE=Mr. C4]Guys,
It is an exhasut fan, drawing hot air out of the engine comparment, 1999Porsche911 is incorrect in saying that it is drawing outside air in to the engine compartment, unless he got the polarity wrong.
For example, Manthey Racing has relocated the fan to the center of the lid on their GT3MR version and hooked it up to a manual switch. Some of their cars even sport dual exhasut fans!
I open up the lid on trackdays as I pull in to the pit, thinks it's more effective. If you don't want to bother opening the lid, leave the key in the ignition, turned to position 2 and the fan should come on.
Ciao,
Mr C4: The 996 fan is designed to draw air into the engine compartment from the top of the lid. IT DOES NOT suck air out of the engine compartment. Who in their right mind would want a fan to suck air from the bottom of the car, past the headers so the top of the engine could get even warmer? If your fan is not blowing down on the engine, then you have a polarity problem which you need to correct.
[QUOTE=1999Porsche911]
looks like there were a few pre '01 996s that had their polarity reversed and the fan was drawing air out of the engine compartment.
drawing air out from the top doesn't seem like a bad idea as you, as usual (sarc.) so delicately put it. maybe manthey is on to something.. maybe its better for track conditions.
FWIW look at the attachement.
Like I said earlier, who in their right mind would want to suck more hot air past the headers into the engine compartment? The natural design of the lid without the fan is to draw air into the compartment and not out. Do a little test....unplug the fan connection from the senor so the fan is on and close the lid. Let the car idle for 20 minutes and note the engine compartment temp using you voltmeter on the sensor contacts. Now do the same thing but reverse the polarity of the fan so it sucks air out of the engine. You will see that your compartment temp is more than 20 degree hotter.
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