Just purchased a 996 a couple of weeks ago. Still learning the quirks of my first Porsche.

I live in Socal (just moved from the east coast) and the thermostat indicator usually reads around "0" on the "180", similar to other cars I've searched in the forums.

Today I decided to drive to Laguna Mountain Visitor Center via I-8. I didn't realize how hot and arid it would be. The temperature outside jumped from 75F to 95F in less than an hour.

The car was being driven uphill for a significant amount of time and the engine temperature was steadily rising. It got halfway between the white and red vertical lines on the gauge. At that point, I decided to turn around and head down the mountain due to fear of the engine temperature rising beyond the red warning line. Within 5-10 minutes of driving downhill, the temperature gauge returned to the "0" of "180". Bit surprised it would cool that fast since the outside temperatures did not change.

Plenty of cars were heading uphill, so it wasn't like this was in the Mojave desert. I recently drove cross-country in an Audi A4 in much more arduous conditions and never experienced a spike in engine temperatures, even at 120 degrees in Nevada.

Was I right to turn around and head back? Or is the temperature gauge in these cars peculiar?

Possibly related: when I had the car stopped with the A/C on the radiator fan on the driver's side seems to blow significantly more air than the passenger side. Is this normal? Or does the airflow blow in different directions on each side?

 

You probably have a bad fan resistor.
that fans have two speeds, and both should be working equally.
low speed at normal conditions, and high speed when AC on or temp over 200 (if I remember correctly).

 

Yep the fans need tested occasionally, all you do is run the car till warm pull over and with the ac off listen to the fans, they should come on,
When they come on, turn on the AC and you should hear both of them spin up to high speed. (works on my car anyway.... )

 

Good to know about the two speed settings. The previous owner replaced the driver side resistor. Looks like maybe the high setting in the passenger fan is inoperable.

Are these fans in use at highway speeds?

 

First,,,,
Most common reason for heating is the gap between the ac condensor and the radiator fills with junk, the 996 cooling system is kind of a hoover vacuum for the highway..
Get this book, its not a 100% "manual" but has a lot of pics and descriptions that help do some of the basic DIY on your car. I found it very useful pulling my 996 engine to supplement my Bentley and other manuals.
https://www.abebooks.com/servlet/Boo...srp1-_-title13

Second,,,
it depends on the highway speed, I found one of my resistors was bad when I noticed the engine would cool as I went faster...
On a 95 degree day it was fine at 80 but the temp would rise at like > 55MPH..

I did the resistor replacement I found here on Rennlist using heavy aluminum power resistors and made some small aluminum
plates to bolt them to. The plates add heat sync capacity and I attached them in the outlet air stream of the fan duct.

The resistor is the low speed circuit, when its running the fans now it doesn't get near as hot as the factory ones.
I used two of these,1 per side

 

Good thoughts from the guys. Once you have had the chance to go over it with a fine tooth comb to make sure everything is functioning properly, and you want to enhance cooling further, you can consider adding a 3rd radiator as well as replace your 996 oil cooler with a 997.2 (3.8) oil cooler. May be overkill in most geographic locations unless you track the car, but if you are in the desert, may be something to look into. Good luck with solving the issues.

 

Just had my radiators / condensers cleaned, new fan resistors changed for the same issue. I also live in So Cal and do the same run on Sunrise Hwy past Laguna Mountain Visitor center. I haven't tested to see how my car performs since getting the work done - will do so and will let you know

 

How fast were you driving? I’ve found cooling at 40mph and below doesn’t work that well unless the fans in front are on.

The fans only come on if the AC button is pressed [on] or if the ECTS (engine coolant temperature sensor) sees a temp of 96.75C. On my car, a 99, that happens at the last white line. The high speed action turns on at 102C, or if the AC fluid pressure is above 16 bar.

I would hook up the car to a Durametric or equivalent and check both low and high speed fan operation, as well as checking the ECTS against what your gauge is reporting. It could be that the gauge is showing higher values than what the engine is actually experiencing.

But yeah, I would have turned back around like you did as well. That was good thinking.

 

+1,,, I put the 3rd rad in when I put the new engine in. I replaced both the radiators then added the 3rd, I used the CSF units. they are well made and are thicker than stock, have a lot more tube area. even on +100 days mine barely gets to the middle of the 0 in the 180.. I highly recommend a lift when doing the full rad replacement, its not hard just fiddly and I'm older so I don't like laying on the ground any more.. I used a portable scissor lift, quick jacks would be cool too.

 

When I was much much younger, I drove cars in the mountains of Colorado, Utah, California and so on, and one thing I learned, as the altitude goes up the temperature in the cooling system rises. In fact, the highways and roadways up in the mountains have special pull off areas so you can stop and let the engine cool down. Don't shut it off but just let it cool down from the work of driving up mountains. I had to do that many times over. Sure, check everything out to make sure your cooling system is tip-top. But as the climb and drive go up, so does the temperature because of the work the engine has to do, and with the twisty mountain roads not as much air is passing through the radiators.

 

Not to curse myself, but having driven my 04 996 three one way trips between Phoenix and San Jose this month, I’ve been very impressed that while it’s over 110 F outside, the AC in the car runs great, and the temp gauge never went past the middle of the Zero in 180.

Obviously, check the resistors and that the radiators are clean, but you should not need a third radiator, or to upgrade the oil cooler…..

-Eric
04 996
99 986

 

Its hard to compare, but I think the biggest benefit of the center radiator is consistency, the car just doesn't change the temp as much as before the triple set were in..
But since I'm also running a new engine with fresh tuning to match ,, its hard to put a nail in the most important part of the changes.. I think in slower traffic it also runs a couple degrees cooler.

Its not earth shattering in any condiditon. Of course my motor is a 3.8 when it had 3 rads it was a 3.6,,,,

 

Maybe 40-60 MPH on a steep incline for 15 minutes. Got stuck behind an older Jeep going 40 MPH so maybe they were having a tough time getting uphill. My A/C started to weaken as well so maybe the engine dialed back the A/C to reduce heat consumption. Everything went back to normal as soon I started to coast downhill.

I drive regularly in the city and on the coast and the engine temperature gauge doesn't fluctuate much. The previous owner replaced the coolant tank a year or two ago if that matters. Radiators look fairly clean from the quick visual inspection. If Honda CRV's were doing fine uphill I dont think it was too arduous of a mountain.

Maybe the thermostat should be replaced? For now ill just stay out of the desert mountains until winter. I imagine if the fans were really bad the car would overheat at idle.

 

The air conditioning got warm because the condesners can't shed enough heat from the freon in the hot weather. My 996 did the same thing a few weeks ago during the hot weather we had in Los Angeles. The engine coolant temp went past the last white line. I turned off the air conditioning and the engine cooled down to a safe temp.

 

At idle, the engine is producing maybe 5-8HP worth of heat, versus 100HP going up the mountain.

The CRV probably has a much bigger radiator and cooling surface than the 996, and so the 996 requires a lot of airflow across the radiators to cool properly.

At the end of the day, it’s the airflow across the radiators that will cool the engine. Driving at 40mph is going to still require fans at high speed to do the cooling at that load level. I’ve found low speed fan operation is enough to keep the car at a decent temp for around town driving and keeping the car from getting too hot, but when the hammer goes down, if the car isn’t going 100MPH on the autobahn or on the racetrack (cup cars don’t even have fans), those fans will have to run on high speed, and that should keep the engine cool enough.