996 Cooling solutions

Okay, Texas heat is about to light up. I've had coolant tanks bust on me, numerous leaks appear from the line connections, and every wonderful problem I'm sure you guys have encountered. That being said, I've got to ask...what is a simple, yet feasible mod that can be done on these cars to less complicate these weather compatability problems?

1. Take off front bumper and clean out all the crap that blocks the radiators 2. Run the proper oil 3. Make sure you do NOT have the leaks you were talking about. I do just fine and trust me, my heat here in Vegas is much worse.

You said coolant tanks (plural) Some 996's had problems with the original tank and cap, but once replaced, it should be fine. As far as I know, there are no other problems with the cooling system, other than the around town engine temps are pretty high, but should not caused any blowing of line, etc. Specifically what other "every wonderful problem" have you had?

You could always install the 3rd rad option, its around $500.00 and it really does help, also an old drag racing tip, use water wetter it brings it down at least 10 degrees..

I would say 3rd radiator if you are worried about cooling.....

applying static pressure will also lower boiling points. Keeping the inlet ducts clean is a great start! Water wetter also helps.. Maybe try some Liquid Cosworth ...

ALso make sure your drive side fan is coming on. Not sure what year you have but from your name I would guess it's a 99. In the past two months we've replaced the resitors for the driver's side cooling fan at least 4-5 times if I remember right. Basically the resitor had gone bad and hence the driver side fan wouldn't come on and cool properly. That and of course the leaky coolant tank in the rear. Other than that the 3rd radiator is a good good thing

turn up the heat in the P and this will bring the engine temp down....JUST KIDDING!!!!..but it really does!!

If you want your engine to remain cooler (190F rather than 220), simply do my fan switch mod. No need for heaveier 3rd radiator. Radiator Fan and Engine Compartment Fan Switch Mod The 3.4 996 runs extremely hot when driving around town in temperatures higher than 75 degrees. This mod is a way to reduce coolant temps back to a safer level, helping to reduce oil temps and improving performance. The mod consists of installing a switch that will allow you to turn on the high speed radiator fans at any time, while maintaining the automatic operation of the fans. We do the same for the engine compartment fan. Radiator Fans Connect a wire to the ground of the 2 high speed fan relays located on the relay carrier located in the driver�s side foot well. The relays are #20 and #22. Feed this wire to where your switch will be located. Connect the wire to one side of the switch. Connect another wire from the other contact on the switch and then connect the other end of this wire to a chassis ground point. With key on, this switch will now immediately turn on both radiator fans providing maximum cooling. When you turn the key off, the fans will continue to run for about 5 seconds until the relay shuts down. Your fan operation remains normal when the switch is off. Engine Compartment Fan Connect a wire to the ground of the relay located in the relay carrier behind the passenger seat, driver�s side. Relay #8. . Feed this wire to where your switch will be located. I simply fed the wire along the driver�s side of the car and under the door sill. Connect the wire to one side of the switch. Connect another wire from the other contact on the switch and connect the other end of this wire to a chassis ground point. With key on, this switch will now immediately turn on the fan drawing air into the engine compartment. When you turn the key off, the fan will continue to run for about 5 seconds until the relay shuts down. Your fan operation remains normal when the switch is off. This mod helps keep the engine compartment much cooler when driving around town and is particularly beneficial to any engine that draws its intake air from inside the engine compartment, such as the EVO SC. If you are adventurous, you can automate the operation of these switches so they will switch off at a specific speed, or operate when vacuum is present only, etc. You can choose any style switch you want and even use Porsche switches. I simply used 2 toggle switches that I installed in the batwing, Jim

Thanks everyone. The *&^$ I've had to deal with is my car overheating. I'll be on an interstate and my car will refuse to idle. It's refreshing to know I can use my car everytime I start it. Besides, I've never had an RMS issue. Seemingly, I'll take the cooling mods over a new eng. So this is basically what it came down to and Thx, 1999Porsche911, for your, and everyone else's input. Later. -99_Carrera

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So, when I bridge the ground wire to the chasis, the fan comes on. However, during "normal" operation, the fan will not come on. How do I tell if I have a bad relay?

What Dell said. I've been in 100F+ (up to 119F) heat with my cars with no problems. However, a properly functioning cooling system -- radiator ducts clean, radiator fans and compartment fan working right, and a pressure tight cooling system -- is a must have. Sincerely, Macster.

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Go to home depot and buy/install a manual coolant flow shut-off valve. Your A/C uses a reheat/remix technique to moderate the temperature of the airflow exiting the system. Until you install the valve use a bit of non-intuitiveness, turn the cabin temperature setpoint all the way down to MAXIMUM cooling and put it in recirculate mode. That will bypass the reheat/remix mode of your A/C, making it substantually more efficient. Now use the fan speed to control the cabin cooling comfort level, but being sure, certain SURE, to turn off the windshield airflow ducting path. You don't NEED a thoroughly CHILLED windshield which might suddenly fog over outside with a high Rh. The reheat/remix technique results in lowering the efficiency of the A/C system so much that the compresor must run continuously in a HOT climate. That adds, substantially, to the HEAT load the engine cooling radiators must operate under/with.

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Macster when you ran in over 100F heat what was your temp gauge reading on average?

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In the case of the Boxster in 116F heat the actual coolant temp climbed to 226F and stayed there and bear in mind at 216FR the radiator fans are running at high speed. Intake air temp was 135F and stayed there. Everytime I slowed down enough I could hear the engine compartment fan running. I think it stayed on all the way across AZ... The coolant gage needle I can't be sure where it was but I know it was quite a ways over to the right of where it usually hanges out, but not in the red and no warning lights ever came on. After the trip and back home and at the dealer I submitted the above to my SM and he forwarded it to factory and the word came back as long as no warning lights came on/flashed nothing bad happened. I can't recall now what year that drive occurred, but it was either in 02 with around 25K miles on the car or in 03 with double that miles. In early 04(Feb/March) the car had around 80K miles on it but I was back in CA by then living/working here and didn't venture down into AZ for some years. (Oh, I like to mention that at the time I encountered this heat the engine had Mobil 1 0w-40 oil in it, fresh with approx. 1000 miles on it, courtesy of the good people at Niello Porsche in Sacramento who did an oil/filter change on very short notice when i dropped in after driving down from Eugene OR!) For the Turbo I did not collect any real data during the time I was in 119F heat with the car. However, from some monitoring of its vitals in earlier experiences with high ambient temp driving -- 107F to 111F (in late June no less!) in places on 84 in the tri-valley area where I live -- I knew the Turbo runs quite a bit cooler than the Boxster, and hardly breaks a sweat even in high ambient temps. From what I can recall the actual coolant temp stayed in the 196F region. Now like the Boxster in AZ I had the A/C on and while the Boxster's autoclimate control labored to keep the cabin below broiling -- it is a fine system but this heat just overwhelmed it -- it was Hot! -- while the Turbo maintained 72F cabin temerature without a whimper. I learned early on the aerodynamics of the Turbo and this includes the flow of air through the radiator ducts is light years advanced compared to the that of the Boxster and since then I really don't keep that close of tabs on the Turbo like I did the Boxster. Also, I've been testing a data logging device I've been working on now for awhile in my Turbo (and Boxster) and these logging devices need to stay connected for long periods of time during testing so I can't do a quick connect of an OBD2 data logger at various times to see what's going on with say coolant or intake air temps. (Oh, during a long drive (coast) down a steep grade in rather cool temps I was taken aback to note the Turbo coolant gage needle had dropped a few needle widths below where it usually resides.) Anyhow, in the case of the Turbo the coolant temp gage hardly moved from where it resides under less extreme heat driving. Sincerely, Macster.

Thanks for the info Macster. I live in Dallas where its regularly over 100F which it will be today. This is my first summer with this particular car. My temp gauge seems to be running around the 205 - 212 range in the heat of the day. This would be the needle being on the right side of the zero but not over the next line which is 215. I assume this is normal then. Can others that live in hot climates let me know what thier coolant temp gauge normally runs at?

I did Jim's radiator fan mod and it lowers the temps by 15-20 celcius...!! I also have the 3rd radiator and it does nothing for in town driving... the fan mod works better..... if your tracking do both for more protection.

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On a 95F - 100F day mine will show 89-91C on the highway and 100-108C in traffic. All with the AC on, clean radiators and using the HVAC function available on the early cars to monitor the temperature. I think an air-oil cooler would take a lot of load off the cooling system. Maybe I'll add one.

Thanks Doug. I did a lot of driving the last couple days in 101 - 104 F temps and tried wwest's recommendation of using the recirculate mode. It ran cooler mostly around 200 - 205F on the gauge while up to speed which I consider good for those conditions. I did hear the high speed fans kick on when stopping at a red light or in traffic. My radiators are also clean and coolant system has been pressure checked.

just do the high speed fan mod... on a super hot day the fan mod will get you down to 85C guaranteed... without fans I'm @ 104C (as display on HVAC) after running the fans for 20 minutes I go as low as 83C... just keep them on in city driving... works like a charm...

I drove my car hard for the past two days in the mountains at about 95 degrees F. My temp never got above 180, even when pushing the car pretty hard. FWIW, I had new radiator fans and relays as well as a new water pump installed last year.

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really? hmm something is wrong then...

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Jim, do you have any photo's of how you connected the wires to the ground of the relay and where the closest ground points on the chasis are ?

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Don't the fans run on high when the A/C is on regardless???

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I don't think they do... when I listened last time I don't remember then coming on... but running the AC will make your engine hotter...

I think they always run when the a/c is on...

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Jim is prob not gonna answer, he's been awol for awhile... I think he misses Ben. I put 2 micro switches (front/rear fan), the ground is hooked up behind the panel braces, there are some screws behind there attached to the body. Unplug the fan relay and tie the ground on the relay prong and put back in the socket... its a no brainer. IMG_0093.jpg

[QUOTE=redridge;9638509]Jim is prob not gonna answer, he's been awol for awhile... I think he misses Ben. I put 2 micro switches (front/rear fan), the ground is hooked up behind the panel braces, there are some screws behind there attached to the body. Unplug the fan relay and tie the ground on the relay prong and put back in the socket... its a no brainer. Thanks ! thats helpful.

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The fans should come on at low speed and run constantly when the AC is switched on, then IIRC the high speed fan kicks on when your coolant temp reaches 216F.

I did the jumper from the low relay to the high relay for each side so when low speed kicks in high speed comes on by default and added one switch for both the radiator fans and the engine compartment fan on the bat wing. I use a mix of 70% water, 30% coolant and added 2 bottles of Water Wetter. My car now stays at 96 to 99 degrees C on the A/C display with that trick with the buttons. Its a huge accomplishment because a couple of years ago it was cooking hot at 110 to 115C with straight coolant, no fan hacks or switch.

Just caught this thread...is over heating an issue with the 996 in hot climates? I fight this with my old '88 Carrera but I assumed Porsche had finally addressed this...

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Relative discussions.. I doubt anyone in this post is speaking of literally "overheating". I think it's more of staying below 215 degrees which is far from being close to overheating.

bumping an old thread. Are there low speed and high speed fans or is it one set of fans with two speed settings?

One set two speeds. With a resistor to determine which is chosen. The resistors can burn out and compromise the system.

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996 works well in HOT climates w/HARD driving just as long as fans/blowers are all fully functional and radiator/condensor air intakes are unblocked. Still not a bad idea to reduce the heat load on the radiators (and get a slight increase in FE) by closing down or disabling(***) the climate control system's reheat/remix cooling moderation technique. ***Install a manually operated water flow blocking valve to prevent HOT engine coolant from reaching the heater core INSIDE the A/C plenum.

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Resistors are OUT in favor of solid state semiconductor PWM power switching for inductive devices. Or in some cases running 2 fans, low speed in series, high speed in parallel.

Questions about the fan mod that allows both radiator fans to run at high speed with the flip of a switch. With the hot summer weather just around the corner coupled with the fact that these cars(996s) engines like to run really hot, I'd like to do the fan mod to my 996. I'll be the 1st to admit that I'm not an electrical engineer, so I have a couple of questions for those of you who have already done this mod(or are electrical engineers...LOL). The 1st page of this thread has instructions for performing this mod but they are a little unclear on some of the fine points. I will be using a toggle switch for the mod and I understand that one connection on the switch will be the ground which will run from one prong on the switch to a ground location on the chassis. Should I simply run it to any chassis screw location near the relay panel by loosening the screw and wrapping the wire around the screw before I re-tighten the screw? As for the second prong on the switch(I'm assuming it takes only a two-prong switch...is that correct?) which is connected to the ground location on both high speed fan relays(relays #20 and #22), how do I go about making these connections? Do I run two separate wires, one from each relay, and then attach both of them to the same connection on the switch? Also, what gauge wire should I use for this mod? TIA for any help...

^ +1 A picture of the relays involved would be great. Electrical work always worries me..I imagine flipping the switch and frying all my computers in one shot.

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Here's a link to a relay diagram for a 2000 Boxster, which I believe has the same relay panel(and layout) as the 996. http://www.theschillings.com/boxrelay.htm

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or this can be accomplished as you previously mentioned by running the AC on MAX cooling, recirculate mode and no windshield flow right? I am assuming you are using a cabin fan speed of 1 (lowest) so it doesn't freeze your face off here...

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Thanks for the link. I was hoping someone would post up a picture of a relay to show which contact to wire into, but maybe its simpler than I think and only has 2 which are clearly marked +/- ?

Took a look at my relay set up and its a bit different than the diagrams DreamCarrera posted (though that was appreciated) It seems that most of the people doing this mod are Mk1 owners and for MkII they changed the layout. The second row up where 19-22 are in Mk1 is largely blank on mine. Its possible that these were simply moved to the bottom row so I removed one and took a pic. Can anyone verify if these look like the Mk1 fan relays and if pin 87 is the one to wire into? Thanks for any help

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Thanks for clarifying this...I should have mentioned that I believe the relay panel of the 2000 Boxster, for which I posted a link, is the same as a 996 MKI relay panel. From your post, it definitely appears that the MKII panel is a bit different. I'm still hoping someone who has successfully done this mod chimes in to give us full details on doing this fan mod. OT: Brett(BAD.TAG), I clicked on the link in your signature...WOW...awesome photos!!! I'm a huge Grand-Am fan and really enjoyed the Grand-Am action shots on your site.

My 996 has been running a little hot lately so I checked it out over the weekend and at least one of my relays is inop. Will replace the relay. Thanks for all of the good advice.

Thanks! Always nice to hear your work is appreciated . Let me know if you have a particular fav and I'll give you the RL price

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Thanks for the offer but unfortunately I have more wall art than I have walls. Hopefully others here will take you up on that RL price though. They really are great pics...would look great hanging in the garage, game room, office, etc.

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Also, remember that the ballast resistors(located behind each fan in the front wheel wells(total of 2)) control the low speed setting of the fan to which it is attached. These resistors are known to go bad. I believe it is far more common for the resistors to go bad than the relays, although it is far easier and cheaper(you can simply switch the relays around to test) to test the relays. When the resistors go bad the fan will not operate at the low speed setting, although it will continue to turn on in the high speed setting when coolant temps reach approx 102 Deg. C. So if after changing the relays(there is a low speed and high speed relay for each fan(total of 4 radiator fan relays)), your low speed fan setting still does not work then you know it is a blown resistor on the side that is inoperable. A quick way to check the low speed fan operation is to start the car and turn on the AC. The fans will always run at low speed(unless the engine temp is too high, in which case they would run on high speed) while the AC is on.

Hi all, I've just picked up on this and have a few questions if anyone can advise. Did anyone figure out which was the ground on the relay? I've read the posts and can't find an answer and when you run the two grounds from relay 21 and 22 I take it you connect both to one side of your switch and then run a ground to the chassis from the other side of the switch. I'm thinking about a gen Porsche switch as I've got a couple of spare slots, has anyone tried this?