Engine Close to Overheating in Desert Climate?

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 Amazon Amazon

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

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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,,,,

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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.

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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.

You can add a manual switch to the high speed fan relays letting you turn them on whenever while still retaining the automatic control, even at highway speeds having the fan running will help pass more air. If both fans are completely broken then the car will overheat at some point when idling, however the dual fan dual speed setup is somewhat failure tolerant in that the car can still decently cool itself with only one fan, or a fan only working in one mode. The 3rd radiator helps as you have more coolant and more cooling area, but it doesn't have a fan so you do need to be at speed for it to be contributing, plus you then have to figure out where to route the output air (or if you really care about it, more of a track consideration).

Well happened again today going up the mountain albeit temps were in the 70s instead of 90s. Pulled off to the side of the road and idled for about 10 minutes and the engine temp dropped back down to normal. Had the A/C on. Glad I was at the summit by then. The rest of the way was flat or downhill and engine temps remained normal. I turned off the A/C as well. Turned into a lovely 3ish hour drive round trip. Fans appear to be working. The passenger fan appears to blow air from below the bumper here where as the driver fan blows straight out of the grill opening. Is that normal?

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Both fans should suck air from the front and dump air into the front tire area.

My guess would be that there is an issue with the fan that is blowing air out of the front bumper as the fans should be blowing air into the front bumper

Yea the fans pull air from the front of the car through the rad and down out the bottom of the bumper. Did u check or perform any of the tests (pull front bumper or test fans) between the 2 drives? If not why would u think the problem would just go away? Not trying to scare u and im not even sure how hot u got your motor as the gauge sucks but a poor performing coolant system in these cars is the kiss of death and a good way to spend $25k on a rebuild.

Chess, if you don't have the DIY skillset, best thing to do is find a GREAT indy that knows the 996 extremely well and have them go over your cooling system with a fine tooth comb. I'd be a little worried if my 996 was overheating going up a long hill. Good news is that its fixable. Don't forget to change your water pump as well if it hasn't been replaced in the last 7 years or so. The plastic fan blades can break off and get lodged in the engine causing cracking from excess heat. No biggie, just replace it every so often. These cars are really durable as he'll. But parts have to be replaced over time. Remember, it's a 20+ year old car. Plastic and rubber deteriorates with use and age. So does metal from friction. If yiu want an engine refresh checklist, just let us know.

i've crossed 7000 foot mountain passes at 100F+ and not budged the needle past center of the 0 on the 180... Oh and I was averaging 85mph.. +1 on your fan being screwed up, it should have 2 speeds on each side pulling air in the front and blowing it out the wheel well. Someone has done something fairly wrong to get that fan to run in reverse. And if they did that I would suspect everything, its not a easy mistake to make. I agree with the note above, pay a good indy who knows 996 cars, don't assume an air cooled shop can do it. The 25k repair bill is no joke, one of the more common fails is a cracked cylinder or head from overheating.... With warm engine sitting parked, both fans should be running at low speed, turn on AC and both fans should spin up to high. If something isn't working stop driving it.. Till its fixed. If your temp goes past the 180 something needs attention unless your in super crazy heat, or in severe stop and go traffic for a long event. .

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That helps Having been on the track several times, my engine and brakes always get hit when I have to come off the track suddenly with zero airflow after hammering the car.

From your description it sounds like one of your fans is rotating backwards. If you're going under 50 you'll see the temperature creep above its normal range (between 180 and the center of the "0"). I had a similar situation to yours a few months ago. I was driving aggressively up a twisty mountain road in 70� temps. I was in 2nd gear most of the way and going between 20 and 50 MPH. By the time I got to the top my temp was halfway between the last line and red zone. High revs and slower speeds. If you're at freeway speeds 50+ they'll usually stay nailed at 180� all day no matter what the temperature is. These cars really like 50+ MPH air flowing across the radiators.

on a 100 Degree day, I was cruising on a stretch of interstate in eastern Oregon before I got my engine done, The temps literally went down the faster I went.. (Only meybe I was in mexico... ) Mine used to get up tp about 200, but as I sped up past 55, the temp dropped till it was stable at 180, and speed was 95. Did not take long at all.