Is My ?99 Carrera Running Too Hot?

Backstory: I�ve noticed the gauge ticking up to the third bar a number of times, but it�s always kicked back down. Today, after some hard driving I got stuck in traffic. Outside temp was 81F. It never dropped down below this point, even after driving at road speed for 10 minutes. Should I be concerned?

I'd be concerned at that oil pressure....was the engine running in this pic????

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😂 no it was on AUX. The oil pressure when running is of no concern.

Normal for the 99�s My �99 runs like that whenever the low speed fans are not on. My low speed fans come on (Ground to DME control unit, terminal 35) at the last white line, which is approx 96.75C, or when the AC button is pressed (on). The high speed fans come on (Ground to DME control unit, terminal 36) when the Coolant temperature > 102�C or air-conditioning fluid pressure switch closed (coolant pressure > 16 bar).Note: The electric fans for the radiators are only triggered when the engine is running If it bothers you, go ahead and have the AC button on, even in the winter. The DME will not destructively run the AC compressor if it�s too cold out

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Thank you! I wasn�t noticing any negative downsides like power lags or a hot smell. She�s new to me so I�m still learning her.

My 2004 runs just past 80 (or 180 in your case) and rarely gets past vertical. The other day in 30C (86F) in heavy traffic the needle was just vertical. We were stop/start for 20min (all 1st gear A/C running)

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I recommend you mod the radiator fans so you can manually switch them on. I recommend you switch to a lower temperature thermostat. And I also recommend you replace the water pump if it hasn�t been done within the last five years. Coolant flush, too. edit: another recommendation - clear any debris from your radiators. You�ll probably have some debris stuck between the AC condenser and the radiator, and removing the bumper makes the job easier.

My '99 has been hotter, about half way between the third and fourth (last) line, once or twice. I replaced all three radiators (it has the auto trans) recently. Now it does not get past the end of the 0 in 180.

Looks hot to me. When I tracked my old 996, it would get to that temp when pushed. I assume you are just doing street driving. Did you clean out the radiators? Amazing how much crap can be caught in them. That's where I'd start. Plenty of threads here on how to do that.

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This is all well and good, but it will not reduce his temps in bumper to bumper traffic.

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I've seen mine creep up about this high. Low-speed traffic seems to be what make it run that hot. As soon as there is airflow going through the rads (30+mph), the temps start to go back down. Even when getting to the top of the Stelvio pass, it wasn't quite this high. Running the AC seems to slow the needle somewhat, but it'll still get there given enough time in bumper-to-bumper traffic. Not that surprising when you consider the second white line is 80C and the third 100, since the fans only kick in around 97.

I would just check & clean your front radiators. Aside from that your car is operating correctly.

I recenetly replaced water pump with new (oem). I also added LN Low Temp thermo. My rads are clean. New coolant. But mine also runs hot when I take a drive up the canyon. It gets to that line, but it never goes past it. I would like to add the fan override switch to see if that does anything. The low temp thermo seems like a good idea if you live in a temperate climate, but if you live anywhere hot, the thermo is going to come on one way or another, and coming on a little earlier doesn't seem to make much difference to the operating temperature in the end. But yes, it does seem other's 996s run a lot cooler all the time, and thus this opens much debate on, or maybe the later models have something hidden that keeps the needle lower so it causes less panic

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tip cars have the third radiator OP def check to make sure both low speed and high speed fans are coming on. Ballast resistors are a common failure point. My PPI said fans were OK, shop missed that low speed fans were not working tho, easy to miss. Both resistors were shot, easy fix and car runs significantly cooler now. durametric is easiest way to test. Also, gauge is unreliable, durametric can give you the coolant temp DME is seeing, or you can do the climate trick to get that info

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I think it�s a bit high. A few people have mentioned it, but since you�re new to 996, debris getting embedded in the radiators is a �thing� with these cars. Removing the front bumper to clean them isn�t difficult - hardest part is keeping track of the various screws and where they go on reassembly. If you don�t have any record of them being cleaned, they likely need it. I also recommend using some evaporator coil cleaning spray on the radiators after you�ve removed the debris, and then rinse with a hose (a lot of additional dirt came out from between the fins after spraying the cleaner and rinsing). That will likely lower the temp if they�re dirty.

I appreciate everyone�s input. The water pump is new (less than 2 years old) and I drove this car through multiple mountain passes for five hours without it ever getting as hot as it was showing in the picture. This may have just been caused by a combination of the heavy traffic and higher ambient temperature outside. I drove the car for over an hour this morning without the needle getting past the middle of the �0�. I also checked the rads last night and they seemed rather clean. The fans were indeed blowing. Thank you for pointing out that the third notch is not representative of an even scale. It makes me feel a lot better that there isn�t a lot of temp between the second and third white lines. With all of that said, I�ll out in a lower temp thermostat next time I service the car, just to be sure. Once again, I appreciate everyone�s input.

OEM GT3 thermostat starts to open at 167F so there may be something there. Possibly cheaper? Never priced it out & don't know if it interchanges on M96.0.

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Hopefully somebody will correct me if I'm wrong, because I don't remember how mine looked from the outside before removing the bumper, but I think you don't see the debris until you remove the bumper -- then, it's usually a pretty surprising amount if they haven't been cleaned. If the temps continue to stay low, no need to rush on cleaning, but just commenting that I don't think the look from the outside is that accurate of a test.

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100. Mine looked clean. Then I removed the bumper. Swear a bird had nested in there so many leaves

I once cleaned the inside of my rads 6 years ago and never again since. We�ll, I do spray them with a garden hose every time I wash the car. Honestly, the idea of having to remove the bumper as part of routine maintenance is kinda funny. Sure, there�s gunk back there, but I really don�t think it has a massive input on reducing temps all that much. And in fact, it only matters when the fans are running or the car is pushing over 40mph (below that, airflow isn�t that good). The rads are on the outside with the AC condensers behind them, which is often the opposite of how other cars work. So if the front looks clean, you�re halfway there. The **** Porsche crowd is part of the reason why Porsche changed the behavior of the ECTS gauge after the 99�s for the 996.2, and again for the 997 (Boxster and others as well), these of which have a gauge needle that never really moves off 12-noon. It�s hilarious this whole thing. I say, go after real data. Plug in an ODBII device or Durametric and record actual values of what �hot� is. Anything above 102C for triggering the high speed fans is about as high as you want, although still not dangerously hot for street use (the pressure at that temp is still probably not even 2psi). This is especially true for stop and go traffic where the engine is generating 5-8HP worth of power and heat. Now, on the track, or up and down some big mountain passes, different story, because you really do want as low a temp as possible mainly due to oil temps and that oil heat exchanger. So for those that do that, a 3rd radiator and all these cooling mods (LTT, etc.) could be worth it. The LTT just buys you more time, but it�s simply a better product.

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You�re right about that, but only if you look at each job by themselves. When performed in conjunction with a manually-overridden radiator fans, it will work spectacularly well. I was pretty alarmed when I read that Rothus was having this issue with ambient temps of 81*F, and they didn�t subside after 10 minutes of road driving. Those ambient temps aren�t that bad, and driving should have made a noticeable dent in the temps. When my car arrived to me, there weren�t any cooling mods done to it. The lowest I�ve ever seen the coolant temp needle was sitting exactly in the middle of the zero of �180�. After I learned about the climate control panel �hack� to display the coolant temp, I would enable it everyday with every drive. At the same time, I jumped the relays for the high-speed radiator fans to run every time the low-speed fan relays were activated. With this strategy, I manually activate the high-speed fans with the AC button. I understand this method has its drawbacks, because the hot air from the condensers is drawn to the radiator, but this was the best I could do when in a rush. They�re good enough, the temps have been decent enough that I haven�t found myself needing to wire them properly yet: to activate them alone without the AC. Anyway, with the climate control panel display and my high-speed fan hack, I noticed my coolant temps would typically remain between 94-99*C The hottest I�ve ever seen was probably 102*C. Even when driving at ambient temps of 60*F, the temps would never dip below 92*C. I replaced my thermostat with LN�s low-temp version, and the temperature was reduced dramatically. At 60*F ambient, I�m seeing 80-82*C. At 83*F, I�m seeing 86-90*C. At 93*F, I�m seeing 95-97*C. The cooling system is fairly good stock, but it�s held back by the thermostat. It closes at a higher temperature when the car cools the coolant down too well. Admittedly, cleaning the debris from between the radiator and condenser didn�t do much; it reduced coolant temps by 1*C. But I neglected to carefully clean between the fins. I shot as much compressed air as I could from the back, but I didn�t put much focus on the details. Despite this, I still think it�s worth cleaning the radiators. I actually noticed my AC condensers had bent fins, so I�m wondering if they�re causing poor airflow into my radiators, hurting their efficiency. I�ll likely replace them someday, but probably not anytime soon with winter around the corner. Also, I compared the coolant temps on the climate control panel with the temps from my OBD2 scanner and noticed that the control panel always reported temps being 1*C higher than the scanner. Another thing I noticed, while sitting at stoplights, was that although my coolant temp would rise slowly, I could lower it by revving the engine to 2k-3k rpm. The cooling system, with the high-speed fans activated, can cool the car down really well at a standstill. The water pump doesn�t flow fast enough, however, which leads to increasing temps. The drawback of this strategy is you look like a fool revving your engine at the stoplight. 😅

@996love I like the way you went about testing and verifying your work to lower the average coolant temps, instead of just throwing something at it and looking to the factory gauge for conformation/verification..

Thanks Porschetech3! I wasn�t logging the hard data with a computer or pen/paper, so I�m basically listing trends from my memory, which can be forgetful sometimes. And thank you for your kind response, because it really does remind me to share this final bit of information which really ties everything together. In my previous post, I mentioned that the lowest temperature I�d see would have the needle of the coolant temp sitting in the center of the zero of �180�. With the aforementioned modifications, my coolant needle would now go as low as the left-edge of the eight. The highest temps I�ve seen this summer, displayed via the gauge, would show the needle at the right-edge of the �zero�. In short, these mods helped with a massive reduction in coolant temperature, and I�m no longer stressed about sitting in traffic.

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Do you have any evidence to back that up? And did the change happen after 99 (i.e. on later 3.4s) or with the 996.2?

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It's pretty much common knowledge.. Porsche is known to react to some silly things their customers complain about.....like the headlights on the 996.1....nothi�g wrong with the Aero improvement over the 993...but Porsche heard the complaints and admittedly reacted with a quick change...

Well, I think I may have an issue somewhere then. Bumper off and cleaned the rads which weren�t terribly dirty. Today I got stuck in traffic, it was 31C outside and I had the screen display on to show me coolant temps� got up to 113C at one point. It seems to always level back out to 108C when I get up to speed but it never drops back down below 105C after driving around a bit in the hills after getting out of the traffic.

Do your radiator fans work? Are you driving with the AC functioning?

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Did you clean BETWEEN the condensers and the radiators? Mine looked great with the bumper off, but when I separated them.......YUK !!!! And lots of YUK !! And check those low speed ballasts for the fans. One of mine was shot and replacing it brought the temp back in spec.

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I doubt the HVAC readout is accurate. Mine once showed 117C, but my DME was showing 99-101C. Plug into the DME and record what the ECTS shows. My guess is that you�re hitting 96-102C max

Unplug and replug the coolant temp sensor a few times to break up any corrosion on the pins.

I�m back to thinking I have no issue with the car. I�ve driven 1200 kms since my last post, highway driving the i5 through Washington St. or pass driving through the cascades, and have absolutely no issues and the temps never getting above 104c even under the hardest of driving conditions up the passes (and I have a very heavy foot). Maybe my car just doesn�t like sitting in traffic!

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Keep in mind this: when you are sitting in traffic, your temps will always increase because there is no airflow. When there is no airflow, no heat is being exchanged, it�s only building. Pure physics. It�s this way with every car, it�s just that most cars don�t tell you this.

This is a normal temp range for a 996 especially in warm climates. You can do various mods to help reduce the temp but the first one would be to make sure your radiators are clean. I assume the fans are working? Mine runs in this range here in Texas (100+) in traffic but once you're able to get airflow it comes down.