Engine Compartment Fan

[Hugh D]

Hey gang,

My car has always run a little warmer than I wanted it to... but nothing crazy... nothing behind the "0" in the 180.

Anyway, my real question is... in 85 degree weather... with the AC on full blast... and the engine hot.... where should I feel the fans blowing. Right now I feel two on the front bumper... (both radiators).... and then ONE on the engine compartment vents... only the passenger side has fan noise and and air rushing out of it. Should both rear vents have noise/air?

Thanks!

[ethand]

Those are the three fans on the car that you are feeling. The drivers side vent is the engine air intake so ther eis not a fan at that location.

E

[Hugh D]

makes sense.... thanks for the response

[FrayAdjacent]

I've noticed that the side fan (engine bay) doesn't come on until the engine as been at operating temperature for a while. It takes the engine oil a bit longer to warm up.

And yeah, the driver's side is the air intake for the engine

[MNBoxster]

Hi,

The Engine Compartment Fan is just that, a Fan to vent hot air from the Engine Bay.

Generally speaking, it comes on to supplement the natural airflow through the Passenger side vent if the Engine Bay Temp exceeds 180°F, but not always.

It's primary purpose is to keep the Fuel and Charge cool by keeping the Engine Bay cool. It is the job of the Cooling System (Coolant, Coolant Pump, 'T'stat, Radiators and Radiator Fans) to keep the Engine cool, so don't look for or expect a Temp Gauge reaction from the Engine Compartment Fan, it won't happen.

It is controlled by the DME which uses several sensors and/or parameters in determining whether or not the Fan should be energized. The actual Engine Bay temp is only one component in this determination. So, it's actually possible to exceed 180°F in the Engine Bay and not have the Fan come on. Because of this, it's very difficult to establish a pattern when the Fan will come on or not

It uses an NTC Thermistor mounted between the Intake Runners for Cyls. 1 & 2 to determine the Engine Bay Temperature and is controlled via a Relay (#8 in the #2 Relay panel (in the Trunk)).

It is fairly common for the Relays for all the Fans to fail as the Fans themselves are pretty high current items. If you suspect your Engine Compartment Fan is running too much, or not often enough, you should swap out the relay. Hope this helps...

Happy Motoring!... Jim'99

PS - The Oil is responsible for removing 60% of the Engine Heat, which it then exchanges with the Coolant in the 'Oil Cooler' (Oil/Water Heat Exchanger). The Coolant then carries this heat to the Radiators to disperse to atmosphere. The Tiptronic S cars have an additional O/W Heat Exchanger for the Tranny.

[porschedude]

Actually, I heard the passenger side engine fan come on for 30 seconds after I parked the car for a few minutes yesterday. I guess that's quite normal if the engine bay gets too hot. Now that it's getting hot in the summer in Texas, I notice the temp needle has moved 1 mm to the right but I don' t think it's a big deal. Some people claim that the debris around the radiator bottom impedes the ar flow and makes the engine run a little hotter. I can only see that happening if there is massive amount of debris. It's a pain to take out the entire bumper to check the radiator bottom. Anybody with simple instructions to remove the bumper?

[FrayAdjacent]

Originally Posted by porschedude

Actually, I heard the passenger side engine fan come on for 30 seconds after I parked the car for a few minutes yesterday. I guess that's quite normal if the engine bay gets too hot. Now that it's getting hot in the summer in Texas, I notice the temp needle has moved 1 mm to the right but I don' t think it's a big deal. Some people claim that the debris around the radiator bottom impedes the ar flow and makes the engine run a little hotter. I can only see that happening if there is massive amount of debris. It's a pain to take out the entire bumper to check the radiator bottom. Anybody with simple instructions to remove the bumper?

This was just posted in another thread... either here or at Renntech (I can't remember, I've slept since I found it).

http://www.realtime.net/~rentner/Porsche/Radiator/Radiator.html

It's a pretty good illustrated guide to getting into the radiators.

I'll be doing this soon, myself, since it IS getting hotter here in Texas. I've seen my temperature gauge a little hotter, but still very much within the normal range.

I'd consider cleaning the radiators as something to do every year, or at least every other year.

[porsche986spyder]

Originally Posted by porschedude

Actually, I heard the passenger side engine fan come on for 30 seconds after I parked the car for a few minutes yesterday. I guess that's quite normal if the engine bay gets too hot.

Yeh, that's normal. I live in Texas too. And mine does the same thing because it's getting hotter now. By the way, I bet no one knows that the fan on the passenger side pulls air in when it kicks on. Most peole just assume that it vents the air out, but after hearing mine come on in the garrage the other day, I held a paper towel up to it to see which way the air was flowing. Sure enough it almost sucked it right into the vent. So, it's not venting hot air out, but pulling cooler air inside to cool off.

[MNBoxster]

Originally Posted by porsche986spyder

Yeh, that's normal. I live in Texas too. And mine does the same thing because it's getting hotter now. By the way, I bet no one knows that the fan on the passenger side pulls air in when it kicks on. Most peole just assume that it vents the air out, but after hearing mine come on in the garrage the other day, I held a paper towel up to it to see which way the air was flowing. Sure enough it almost sucked it right into the vent. So, it's not venting hot air out, but pulling cooler air inside to cool off.

Hi,

Right. Again, that's consistent with a system designed to cool the AF charge, Intake Runners and Fuel Rail. My Turbo Esprit also has an Engine Bay Fan and it too draws in cooler ambient air and operates on shutdown. It draws the air right in past the Carburettors to prevent Vapor Lock if the car is to be started before everything can cool down. It also exhausts this air past the Turbo (to aid in cooling it) and out through the Wheelwell...

Happy Motoring!... Jim'99

[CJ_Boxster]

HANDS UP, THIS IS A HI-JACKING!!!.....
is it normal for your radio to cut out for a split second when the engine bay fan triggers on?

[porsche986spyder]

Originally Posted by CJ_Boxster

HANDS UP, THIS IS A HI-JACKING!!!.....
is it normal for your radio to cut out for a split second when the engine bay fan triggers on?

I would say NO. Mine never does this. Sounds like a grounding problem?