coolant type

I noticed my coolant level is below the minimum line. The manual says to mix it half and half with a Porsche authorizes coolant. Which antifreeze at the parts store can I buy?

Your friendly local Porsche dealer sells coolant. That's the one I use...........

Porsche coolant is "lifetime" (although an occasional flush out is probably a good idea) hence the recommended maintenance interval. Prestone, etc are not.

Depending about how far below you maybe able to add water and Water Wetter. In LV, you're more concerned with boil than freezing. You might be OK with the above. Check with a hygrometer. FWIW, I think Redline's "Water Wetter" is a good idea and added it to mine. regards, Steve

Thank you all

Steve: For how long are you using wetter water? Any problems? I am running a bit hot (around 225-230) in the track when ambient is over 90. I am considering the wetter water but last time I used it on my MRoadster the thermostat died. Maybe a coincidence? Nick

If you car is running hot, adding more distilled water will help and you should flush the system also. Check your fan relay to see if it kicks on too. Get cooling system pressure tested and change thermostat is needed. Water wetter doesn't cool much except it allows you to run a 70% water / 30% coolant mixture more safely.

System was flushed, radiators were cleaned, fans and thermostat OK. The car is fine everywhere (traffic with AC, etc) apart from the track when really hot outside. Maybe when I flushed the system I overdid it with the coolant %. I'll try to lower the coolan %. But the wetter water is supossed to reduce the temp even at 50%-50% coolant-water by 8-10 F. When mixed with 100% water it drops it by 18F or so Redline claims. My concern is if it affects the operation of any componets like pump or thermostats. I've also heard stories of radiators plugging after the addition of wetter water due to a reaction between the wetter and the coolant forming solids???

The high engine temps of the 996 have little to do with the capacity of the cooling system or the fluid that is used in the cooling system. The primary reason these engines run hot is the lack of air exchanged over the radiators. Durning speeds of less than 60 mph, the design does not allow enough air to pass over the fins and properly remove heat from the coolant. This is why these cars regularly have engine temps in excess of 205 - 210F just driving around town on a mild 80 degree day. The only fix for this without changing the design of the radiators and/or increasing the surface of the radiators, is to force air over of the radiator by using the high speed fans and keeping your engine compartment as cool as possible.. Doing this will reduce your coolant temps (and therefore oil temps) by as much as 10%. That means if your engine normally runs 210F, running the fans at high speed will reduce you coolant temp to the low 190's, where it should be. I run around town driving hard in 90 - 100F temps and have a coolant temp of 192 - 194.

SO do you keep the fans on high speed by running with the AC on ?? Is there a mod to keep the cooling fans at high speed ? I have the issue where the temp creeps up if im moving slowly and its hot outside, so i hit the AC to keep the fans running fast

Hook up a switch to the 2 high speed relays in the footwell so you can switch on the fans without the AC on. If you want to get real fancy, install a voltage switch inline to be deactivated by a specific voltage. Then you can hook the switch up to a voltage line such as speed sensor and have the fans turn off after reaching a specific speed. You can also do the same with the engine compartment fan which will reduce engine temps even more. Although running the air reduces the coolant temp slightly, the fans barely offset the additional heat created by the compressor running.

I think that the coolant has a lot to do with the coolant temp. I did some research and found out that the 50/50 mixture water/glycol has a thermal convection value of 897 watt/m^2 C versus 1829 for pure water. In other words 100% water can dissipate heat twice as efficient as water/glycol. And probably when I flushed the system I put more coolant thinking it will be better.

You are correct that water will remove more heat from the engine, but that is not the problem with the 996. So now you have transferred more heat from the engine to the water. What now. The water will again become just as hot as a coolant mixture, or actually hotter. You are still stuck with an inefficient raditator system at low speeds and do not have enough air flow to cool the water to acceptable levels. I have run pure water and it make no difference. If you do, however, increase the efficiency of the radiators, you would benefit but at a cost of having less corrosion protection, boil protection and lubrication in the system. A 40/60 mixture of antifreeze/water is about as far as I would go. Whatever liquid you run in your cooling system, it has to be cooled in order to remove heat from the engine.

Do you have specific instructs on this or a link to Renntech? TIA!

I don't disagree but I am saying is when I flushed the system I ended up putting close to 60/40 coolant/water. That shouldn't help. The switch solution sounds good. Do you have instructions?

It's not a difficult mod. Hotwire the relays whatever way you want to. The fans will still operate as normal when your switch is off. As far as details....run a wire from each relay to a switch and a wire from the switch to a ground. Locate the switch wherever you choose. I have both relays on one switch. The relays are #20 and # 22 located on the carrier in the driver's footwell. Second row from the bottom, far right relay and 3rd one in from the right. Engine compartment fan relay in located under the carpet behind the rear seat. The relay is in slot 8 and is the bottom row, second from the left.

Thanks a lot

Another quick one... Do the low speed fans for the radiator ever do anything ? I have never heard them come on. I parked in the side of the gas station with the motor running and waited to see if the low speed came on. It never happened as far as i could tell, but the high speed did eventually kick in once the temp got close to the right of the '0' in 180. If its warm out i run with the AC on and this really helps to stabilize the temperature. It mainly stays between the 8 and 0.. or ventures close the the left bar of the 0. If the low speed is really not working will this actually make a difference... i read that there is a resistor that controls the low speed that burns out on Boxters. Should i even bother looking for this ?? Thanks

I have never had a problem with the low speed relays for the fan. If you let the car warm up, they should kick in eventually. You can't hear them as much as when they are on high. I notice no benefit when the fans are running on low. By the way...when your gauge is on the line on the right side of the "0", you are at about 215F.