My coolant temp has been high around 230F so I dove in today

I removed the drain plug in the rear bottom of the engine and got 2.5 gallons of coolant to come out. I refilled with a 12oz bottle of Red Line Water Wetter concentrate and 2.5 gallons of distilled water. I watched a video on youtube and learned how to pull the bumper off, remove the ducts and get access to the front condensers and radiators, they were a mess of filth, leaves, cigarette butts and even a flip top off of a can of soda. Put it back together and went for a long ride in the 106 degree heat today. The temp went up to 215 using the HVAC center trick I can get a readout of the coolant temp in celsius. I'm happy, the temp gauge hangs on the edge of the zero in 180 and not on the 3/4 mark like it was. It gets even hotter here so the jury is still out on the outcome of my project but at least I know that the radiators are clean. Distilled water transfers heat much better than coolant. Water Wetter supposedly helps break up air bubbles that stick to the metal surfaces inside the engine and provides the lubricant the water pump needs. More distilled water comes in contact with more metal surface and water gives up the heat much better than coolant when going through the radiator. I raced SCCA for many years and ran no coolant in my C5 Corvette just distilled water and Water Wetter, I believe in the stuff. There are still about 2.5 gallons of 50/50 coolant floating around in my 996's coolant system. The whole system holds 5+ gallons.

When I roadraced motorcycles we couldn't use glycol based coolant because if it leaked on the track from overheating or a crash it would creat a slippery area. We used water + wetter and it worked well.

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Sounds good. Be sure the cap's not leaking. In fact, if an old cap -- part number does *NOT* end in a 03 or 04 I'd advise you to buy a new coolant cap and replace the old one. Both the cap on my 02 Boxster and my 03 Turbo developed a leak. I went though southern AZ a few years ago and it was 116F in the shade and no shade. Coolant temp in my Boxster reached 226F and stayed there for a long time. Car took it well though with no harm. I liked to died though. Too blasted hot for my liking. Just Saturday driving Turbo went through AZ on I-40 heading west back to CA and passed through Kingman and then on into Needles CA and outside air temperature registered 118F in places. Don't know how hot the Turbo's coolant got. I do keep the radiator ductings clean of trash. Not sure how effective water wetter is with nearly 50% of the coolant still anti-freeze and water. I'd think you'd want to drain the system, flush with fresh water, then refill with distilled water and water wetter. Oh, fill with water, ran engine and get cooling system hot enough water circulates to fully flush any residual anti-freeze from the car's heating system. Let system cool down dran and then refill. In this case I think investing in one of the those vacuum coolant refill systems worth it. Takes the worry out of a Porsche cooling system refill resulting in hard to remove air pockets. Sincerely, Macster.

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Just for grins downloaded some OBD data collected during my return leg of my road trip to the mid-west and back. During drive from Kingman to Needles and then beyond to Barstow -- where I stopped for dinner -- intake temp at places reached 129F. (Highest ambient temperature I saw from dash display 118F.) Coolant temperature never got over 190F. Even when I was in stop/go traffic a few minutes in one of the lanes leading up to the inspection station on I-40 just inside the CA state line. 'course, I had the auto-climate control set to auto and 72F and I know with the A/C on the electric radiator fans run all the time which helps to keep coolant temperature lower than it would otherwise be. Sincerely, Macster.

Try the fan mod.... I love this mod.

Did you burp the cooling system after you refilled? My radiator fans turn on at 103 C which is 217 F. Did the fans come on?

My fans come on at 195 and never shut off because with AC on the temp never goes that low at least not now in July here is Carefree Arizona, it was 101 today and now at 8:30PM its 99. The fan mod is great its just blistering hot in Arizona and with the AC on.

Yes burped, ran until temp was up with the pressure release in the up position. Let cool added more distilled water, repeated twice. Not showing low any more. The gauge does not go up to 3/4 any more so in my book.... IT WORKED.

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What is the fan mod? Maybe a bigger fan?

^ Fan mod is a set of manual switches turning the radiator and rear deck lid fans on. Ferd and I did them 6 weeks ago and its is by far the best mod for the buck on the 996. Parts cost $12 from Radio Shack and few hours of labor with electrical wiring knowledge. It keeps my coolant temp down on 87 C-89 C anytime I want instead of letting go up to 103 C and kicking the fans on.

I'm interested in logging both coolant and oil temps on my 2000 996. What are you guys using to log the OBDII data? And what is the "HVAC center trick"?

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https://rennlist.com/forums/7564285-post43.html

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cool avatar.... check out post #43 https://rennlist.com/forums/996-foru...-thread-3.html you can use durametric to log user obd2 data..... just google it.

I use a device called CarChip. Made by Davis Insruments. Disclosure. I work for Davis Instruments and am in fact the senior firmware engineer for its automotive products. If you want real time OBD data you can use an OBD code reader/data viewer. Some of the more sophisticated ones can also store data for some time. I have an Actron unit I've had now since the shortly after 1996. Sincerely, Macster.

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We send items to get calibrated by you guys. Here locally of course.

BTW, Water-Wetter works. Plenty of data to show it does through various mags over the years.

Thanks for the info. The Durametric system looks quite comprehensive. I've seen the Scangauge II and would prefer something like it or the CarChip that doesn't require a laptop to log data. Seems like these record coolant temp but not sure about oil temp. Has anyone seen or used the systems that use an iPhone with a OBDII to WiFi link? BTW Redridge, thanks for the compliment on the avatar. I shot that at the Rolex 24 this year. My car was parked on the east end of the corral close to the ferris wheel.

I'm disappointed because the car ran at 224 degrees F. It ran at 230 F before I changed out the coolant and cleaned the radiators. This is my first summer with this car and maybe this is normal in this intense heat. Here's pics:

I know it is summer and you are talking high temps but shouldn't there be a caution regarding using distilled water in low temps? A frozen water line could be hazardous to your engine's health.

I've seen many 996s where one fan doesn't work at all or only works in low/high. Worth checking in a warm running car. Don't assume that because one fan is on, and sounds like it's working properly, that both are...

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Temperature shown is not normal for street driving. Needle over the left side of the zero in 180 is very warm, any more than that and you may see benefits from cleaning rads /flushing coolant etc. It can handle it, but I haven't tried too much track driving (as I know it gets hotter on the track) as I don't want to cause undue wear or worse. If it was mine i would check the fans are working , clean, flush etc and that should be enough. Regards,

The reflection in the radio display looks more like fire that sunlight. Oh the joys of Arizona summers. Here's one from a drive to Superior last summer.

Do these cars just naturally run hot? Many other cars I've owned maintain a "normal" temp range year round without a fan during normal driving.

I did remove the bumper cover and clean the radiators if you read the post. This morning I went to North Scottsdale Porsche and the service write told me here in Arizona in July with 110+ temps every day 3/4 up the gauge the LINE after 180 in 100% normal. My 996 now stays in between the zero in 180 and the line at 3/4 since cleaning the radiators and dumping the coolant for distilled water with RED LINE WATER WETTER. Yes all the fans are working. This is as good as its going to get, I guess.

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I had the exact same issue here in Dallas where the temps are around 100 and getting worse. I recently had a bad ballister replaced for the left fan which was not running when the A/C was on and also replaced the right condensor which had a slight leak. I could not be happier! If I were you, I would look at a possible bad ballister or fuse, they are known to go out especially the ballister. Then I would look at the condensors for possible leaks...replace if necessary. Car temps are now where they were before around the 8 on the 180 and when making multiple stops and driving her like I stole it at between the 8 and 0 on the 180 but never more. I am looking at replacing the left condensor as well just for future preventative measures. Hope this helps

I just had some similar overheating problems. For mine, it was the bleeder valve on the coolant reservoir. The Tech said it was fairly common, enough so that he keeps reservoir and bleeder valve replacements in stock. BTW - in my '99 C4, I have to replace the reservoir - the screw holding the bleeder valve were completely corroded.

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so you replaced the entire bleeder cap?

Out of curiosity, at the engine temperatures you are referencing, what is your oil pressure at idle? The temperature on our car has never really gone even as high as the 3/4 mark (215?) but the last few summers I've noticed that when the engine is "hot" the oil pressure at idle can get as low as just above 1 bar which seems low. Even when really hot, the engine pressure easily hits 5 bar (or very close) anything past 3,000 rpm. We've had the car for about 8 years now (it's a '99) and I don't recall it going that low when the engine had less miles, but the car uses no oil (touch wood) and while I'm sure it is slightly down on power (the chains rattle pretty good when cold so I'm wondering how worn they are and if there are timing issues) but otherwise seems healthy. I know the owners manual says that at 5,000 rpm the oil pressure should be at least 3 bar which the car easily passes, but 1 bar at idle (even when really hot) just seems a bit low to me. Jeff

I'm convinced my car is running normal. It was 100 degrees at 8AM and it took a good 10 miles of driving at 60MPG for the center display showing the temp in celsius to reach 100C, that's 212F. Later in the day I was driving on the streets stop light after stop light and it was hotter in central Scottsdale on Scottsdale Road 111F at 5PM. My cooling system gauge with the display switched now showed 107C, thats 224F. Drove north 22 miles home and watched the outside temps fall as the elevation increased. In my town Carefree the elevation is 2300 feet and the temp was 98F, the reading now showed 102C, thats 215F. The dash gauge was sitting on the right edge of the zero in 180F. Its hot as hell here and I think its as good as its going to get. Porsche in Scottsdale told me 3/4 up the gauge is normal in this intense heat. Its better since I cleaned the radiators and changed to Water Wetter.

Got a link to the youtube videos? I suspect I'm due for some cleaning as well. Lately the temps have been getting a bit higher than 180, depending on traffic, temps, and my driving. I'll connect the laptop and get some real data.

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this is the reason why you would want the fan mod....

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You can't say that with any certainty. The in-dash temp gage is at best a rough indicator of the coolant's temperature. After I ran through AZ in 116F heat and ran with the coolant at 226F for miles and intake temp at 135F -- even the engine compartmant fan appeared to be running non-stop -- I checked with my local Porsche dealer service department and he checked with the factory and the word back was as long as there were no warning lights on or flashing the engine was ok, suffered no overheating. That was years ago and over 100K miles ago and apparently the engine was not affected at all. Thankfully I had relatively refresh Mobil 1 0w-40 oil in the engine having had it changed just 1000 miles prior to ending up in the AZ heat. I have checked the gage's position relative to the actual coolant temperature and roughly every needle width after 180 is another 10 degs of coolant temp. But these in-dash temp gages vary considerably in how the react to coolant temperature signals from the coolant temp sensor. Porsche (as is true with most automakers) purposely fit dampened gages to avoid wide swings in the needle's travel to avoid scaring the owners. The most important thing is the engine's cooling system must remain pressure tight. Any leak, even a cap leak that allows pressure to escape can under high heat conditions allow localized overheating and this can quickly damage the engine. But as long as the cooling system can maintain pressure under high operating temperature conditions the engine's safe. It is the pressure that plays a major role in controlling any possibility of the coolant flashing to steam at the hottest locations in the engine. Also, one should periodically check the function of the radiator fans. My 02 Boxster's passenger fan stopped working cause the low speed ballast resistor failed. There's sufficient margin to get by on one fan but of course the non-functioning fan should be made functional again as soon as possible. I've cleaned the radiator ducts out several times -- lots of trash -- but never found the engine's cooling any different after than before. The major concern from the presence of trash is corrosion. Sincerely, Macster.

^^^^So is there a quick check to see if both fans are working?

I woke up really early and did the radiator fan mod complete with switch, works like a charm. I did the engine fan mod without a switch for now, it turns on with the key. The forecast was 115 today and I wanted to combat it. Got a new radiator cap-check, cleaned radiators-check, switched from coolant/water to distilled water/Water Wetter-check and now the fan mod front and rear. This morning at 8AM it was a balmy 100 degrees here, drove to work the climate control display trick showed 100C, thats 212F when I got to work. The temp gauge was in the middle of the zero in 180....SUCCESS. Drove home in 115 heat a few minutes ago and the temp gauge was climbing higher and higher just past the 3/4 mark. The climate control trick shows 113C thats 235F, YIKES THATS A NEW RECORD. I read some other guys post and he said he wished his car didn't have a temperature gauge so do I. I have another 12 ounce bottle of Water Wetter and I'm going to add it tomorrow morning after I use a turkey baster to suck out some water from the expansion tank. I feel like all of this work, time and energy has accomplished nothing. I'm renaming the 996 INFERNO.

I've been having similar issues. I did a three day track event this week and the temperatures were running higher than usual (108-112C). I was a little concerned and figured it was old radiators not doing their job. Then I noticed that just cruising around was generating high temperatures. I almost over heated on the drive home when stuck in an hour of traffic at 90F ambient. I'm starting to diagnose things now. It seems like my driver side fan isn't coming on even at 107C coolant temperatures. The ballast resistor looks easy to replace. Is there a easy way to check it's functionality before replacing it?

Mike, it was 91 in Coral Springs today and 115 here. The thermostat is working fine, it kicks in right at 185 degrees, the air discharge from the radiator fans under the sides of the front bumper gets HOT at 185 and gets hotter and hotter so the thermostat is opening and sending the water to the radiators. I think I'm going to start a post and ask others in Phoenix what temps their 996's are running at. Like I said at 100 this morning my car stayed steady at 212F and the gauge was in between the 8 and the 0 in 180.

have you checked the water pump? we had a run of about 4 or 5 water pumps this last week... all were missing fins on the impellers... hell, one was missing the impeller.... hard to move water with a round bushing... you might be a candidate for new water pump and LNE's lower temp thermostat (which I have said in the past I dont fully understand the benefit without the fans kicking in at lower temps, so with the fan mod you should be good)

Edit: It was 98 degrees yesterday when I drove home and my car was a constant between the 8 and the 0 but never went further than the 0. Even in stop and go portion of my commute.

There are two stages of fan speed. Does yours turn on high? A/C only kicks it in low forst.

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Any easy way to diagnose this, short of taking the pump off? S.

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There are two tests one can perform. Test #1 is to drive the car until engine/drivetrain fully up to operating temperature. The AC wants to be off. At some point -- if the ambient temperature high enough and my experience is it does not take real hot day (mid to high 708 plenty hot enough) -- the fans should come on. They come on when the coolant's temperature reaches 212F. The fans come on low speed and run until the coolant temperature drops to 205F. Now you might even with the engine up to temperature raise the engine speed with the car stopped and the transmission in neutral. Run rpms up to 2K or so (higher is not necessary) and hold for 10 to 15 seconds. This will increase the coolant's temperature to the point the fans should come on. Under very high temperature conditions if the coolant temperature climbs higher -- 216F is my info -- the fan speed should switch to high speed. What you want to do is verify both fans come on low speed and run and then shut off as the coolant temp drops from the fans running. Do not rely upon your ears alone. Get out of the car and verify you can feel air flowing into the radiator ducting and out again. My 03 Turbo lost a radiator fan hub/blade assembly. Shaft snapped. The electric motor ran but no air flowed through the radiator. So check that you can actually feel air and air flow through both radiator ducts should be the same as best as you can tell. This verifies fan operation, air flow through the radiators, t-stat operation, water pump operation, and to some extent the ability of the cooling system to maintain pressure. (Doing this above test caused pressure to build to the point the coolant tank in my 02 Boxster split (I suspected it was cracked to begin with). But at least the tank failed while the car in my driveway and not out on the road. BTW, the tank failed at around 233K miles...) Once you are sure the fans come on and go off based on coolant temperature, you can when the fans are off then switch on the AC. Both fans should come on and remain on regardless of the coolant's temperature. Sincerely, Macster.

Sdie bar: You guys running in hottler climates (like hell, Az) should consider using a heavier oil than 0-40 during these hot months. At least 5-40, but 15-50 or straight 40 would be better....

I switched to 15-50 this last change last month. The pressure stays high for about 5 miles or so until it heats up and thins out a bit.

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IIRC neither 15w-50 or straight 40 weight oil approved by Porsche. Mobil 1 0w-40 a bit "thin" (its HTHS numbers lower than comparable oils) but given reasonable oil/filter service intervals (5K miles) the engine should be just fine. I've run through some mighty hot areas in my 02 Boxster with Mobil 1 0w-40 and the engine has not suffered any. And the engine has over 233K miles on it. But I change the oil/filter every 5K miles. (I've since switched to Castrol Syntec 5w-50 oil cause I think Mobil has cut back the quality of its oils.) If one didn't want to use Mobil 1 0w-40 or Castrol 5w-50 (or Mobil 1 5w-50 -- not a typo for 15w-50) there are several other brands of quality oils to chose from that come in the 5w-40 multi-viscosity grade and would be fine and are approved by Porsche. Sincerely, Macster.

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I don't wish to spar with someone who gives as much to these forums as you do but..... Porsche's viscosity recommendations are not necessarily in the best interests of folks living in the deserts. They're more in keeping with their capitulation to the anti-racing greenies of Europe. I have a friend who teaches Porsche racing in Dubai. I just wrote him to ask what viscosity they're using over there in their factory supported GT3's and RSR's. I'd be surprised if it's 0-40....

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We're not sparring. Just having a friendly exchange of ideas. I think I can tolerate quite well disagreement and differences of opinion. If Porsche started recommending 5w-30 or even 5w-20 oils I'd agree the greenies have gotten to Porsche. But a recommendation to use a multi-grade synthetic oil like Mobil 1 0w-40 oil is not a capitulation to the greenies. Primarily what drives an engine's oil viscosity requirements is its bearing clearances and piston/cylinder fits along with the open valve spring pressure (which can result in extremely high pressures at the cam lobe lifter face interface -- a open valve spring pressure of say 170lbs given the very very narrow contact line of the lobe against the lifter face can result in 170,000psi of pressure there which of course the oil must help deal with) . An engine targeted for production vehicles is generally a "tight" engine -- built to have tighter clearances -- to deliver good compression (helps drivability at part throttle (<30%) where most street car engines spend most of their time), deliver good fuel mileage, reasonable oil consumption, and quiet operation. A downside -- minor imho -- is this engine takes more miles, more running time, to make max power. IOWs, break in takes more time though one can speed this process up by following a more agressive break in regimen. I believe this is ill-advised but to each his own. While a thicker oil appears to be a no-brainer choice for better oiling this is not necessarily the case. A heavy oil will run hotter due to hydraulic friction. A heavier oil may actually result in less ideal lubrication not better. I have no real interest in what oil is used in high performance race track oriented cars in Dubai. Especially ones backed by Porsche factory money. Winning is everything and as long as the engine lasts the race who cares about the other considerations. However you might be surprised as to what oil is used. Race engines are a different breed. My neighbor builds race engines and his engines are built to use a special 0W racing oil for as little friction as possible. In the racing application these engines are used all that matters is the engine produce max. power for as long as the race lasts. I'm always leery of advising anyone to step outside of the automaker's recommended oils. I'm not prepared to back my recommenation by any guarantee. Thus I advise any Porsche owner to go with the manufacturer's recommendations regarding oil type, viscosity based on the prevaling ambient temperature in the area the car is driven. I will advise a more frequent oil/filter service interval however. Sincerely, Macster.

I went for a ride just a bit ago without the AC on, the dash showed 100F outside temperature. I drove south on Scottsdale road for 12 miles, I hit many lights and my climate control display for the coolant never exceeded 92C with the radiator fans on HIGH, I have a switch installed. I jumped on the 101 expressway and drive 75 MPH for about 10 minutes and the temp dropped to 91C, thats 195.8F with the fans blasting on high. I got off an exit switched back and headed north to the Scottsdale Road exit again, the temp fluctuated a degree or 2 up and down. When I got off at Scottsdale Road again it was 94C, thats 201.2F. I'm 50 miles into this test ride now. I pulled over when I got off and let it idle for 3 minutes, the temp went up 99C thats 210.2F. I drove north on Scottsdale Road for 5 miles and it went back down to 95C thats 203F. I AM BAKING HOT NOW, the outside temp is 103F on my dash thermometer and I have no A/C on. I shut the windows and turn on the A/C to 75 degrees, center vent and recirculate. On the last 7 miles of the trip I hit 3 lights and when I was in front of my house the coolant temp was 106C, thats 222.8. I don't think that anything is wrong with the car. I think the condenser is heating up the radiator when the A/C is on. Now before you chime in here and ask questions that have been answered, read the post!!!!

Try replacing your cabin filter. It may be clogged and working your AC too hard. Same thing was happening to my AC at the house. Filter was not cleaned in 2 years and AC was crapping out in 100 degree heat during the afternoons. Cleaned it and now works like it should..

How do I get to it?

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open the frunk, the black plastic cover on the passenger side. look under the wiper cowl, it should be lying flat with a foam deflector covering part of it. takes about a couple minutes to do.

Just heard from Dubai, they run straight weights only in their Porsches over there either 40 or 50.....