Still Overheating

Went up to the track again last weekend after thinking my cooling problem was fixed, and now it appears not to be. Here's what I did: Took out radiators and cleaned them cleaned out ducting put in water wetter. After about 8 laps I was pushing 240 and had to pull off and cool the car off. Is my only other option the 3rd radiator?

Have you done the radiator fan mod yet? That will keep the temps low at all times unless you have underlying cooling system problems.

What is the radiator fan mod?

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. 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.

check your coolant resovior?

This really won't have any impact on the track. Only when you're sitting still or moving very slow. Cup cars don't even have fans. JC3D, if your car is hitting 240 while on the track you have some other problem. It's probably time to visit a mechanic. Jim

Sure will and sure DOES. A few of the guys that have done the mod run as much as 15% cooler at the track than before. However, I agree with you that he probably has other problems or his fans are not working at all if he's hitting those temperatures after 8 laps. The mod delivers cooler temperatre whenever you drop below 60 - 70 mph over the stock setup.

That explains it. Why are you under 60-70 mph on the track? I'm not going to argue with you but what impact would the fans have when you are moving at a speed greater than the speed the fans can move the air. Probably around 10 or 15 mph? I actually removed the fans on my old 996 race car to improve cooling. I guess we took opposite approaches to the same problem.

The fans on the stock or GT3 bumper on the 3.4 moves more air over the coils than is acheived driving below 60 - 70 mph without the fans. The design of the bumpers does not permit enough air to pass through the radiators below that speed without fan assistance. The difference in temperature obviously decreases as speed does. Additionally, if your fans are running in slow mode, you are actually reducing the cooling effect when at speed. At high speeds, removal of the fans reduces the restriction of airflow and that is why the fans are not necessary. It is for speeds below 0 -70 mph where this mode has great benefit. Anytime you drop below that speed and the fans are not on high, your engine temps will climb. This is why controlling the fan relays based on your speed sesnor can be beneficial. This mod can drop your coolant temperature on a 90F day from 235 to 200 in a matter of minutes and maintain that temperature quite consistantly. Driving the car described above in 80F temperature at a speed of 50 mph, the coolant temp will be approximately 8% higher than the same drive with the fans running. With fans running your coolant temp will maintain itself below 200F in the same driving conditions. Running the engine compartment fan also helps maintain reduced temps. Obviously, removing the fans on his street/track car can't be done.

OK, like I said, even though I don't get how it can help I'm not going to argue. You have the switch in your hand and can see first hand what's happening. Back to the original poster. Clearly he's got bigger problems that probably will require a mechanic. Don't run your car hot too long. Jim

So - either the car really is hitting 240, in which case your block is in serious trouble! Or your gauge is reading false, and it just looks like you're running hot. You got any other symptoms? Loosing coolant - no heat in the in-car air feed - water in the oil??? I'm thinking air lock in coolant system maybe? Or faulty thermostat? Failing water pump? Either way - time to get to a decent mechanic Suggest Hergesheimer Motorsport in your neck of the woods Laura from HM is on this forum quite often, and they know their track cars. http://www.hergesheimer.com/ 20612 Ca�ada Rd. Lake Forest, CA 92630 Phone: [phone removed] Fax: [phone removed]

FWIW I have the fan mod...and LOVE IT...but then again I am not on the track and stuck in LA traffic....sigh.

It could be the low speeds, this was happenning at streets of willow. While on the big track at willow a few weeks ago when it was only 10 degrees cooler, I had no problems. My car did this when I first bought it. Since then, I have had to replace the engine so I am ruling that out as an issue. Also ruling out the coolant resevoir since I just added the water wetter. No leaks or anything. Cleaning out the radiator at first seemed to work. There was a lot caked in there. I guess I will start to go through the rest of the cooling system and hope its not this hot in a couple weeks when I go back to streets. But may be this fan mod might work for a low speed track like streets?

I haven't worked on my 3.4 much. On other makes, air in the coolant system always lead to hotspots in the engine and overheating issues.

Good point. Air in the system is an issue on 996s but they usually burp out fairly quickly. One trick is to leave the bled valve open at the track. We never close it on stock 996 race cars. The cup car manual says to leave it open all the time.

FWIW I leave my blead valve up/open all the time and will also overheat if I keep pushing hard at the track on a hot day. I watch the temp and as soon as the digital read out gets too high I start to take it easy otherwise the overheating light in the temp gauge lights up. In my case... I have no cracked expansion tank... Coolant is topped off, A new cap, still need to take off the front bumper and try to really clean the radiators out. Any other ideas??

What is the coolant's temperature when you say it is hot? Are both front fans running full speed?

Car could be running severly lean if it has headers, exhaust, CAI and others without reconfigin' the ECU. Maybe needs a little fattening up, should drop coolant temps.

Digital readout hits 118C-120C and then the light on the guage comes on unless I back off and do a cool down lap and then I can keep it at around 115C but keep a close eye on it on the straight aways. Well just now... I took the bumper off and cleaned all the crap out in between the ac condensers and the radiators... lots of junk. I am instructing this Sun so will see if I notice any benefits. As for the fans.. they run when I have the AC on but I never really have any issues around town, only at the track. Car is Stock... just has fabspeed mufflers everything else is bone stock.

First thing I would look for is coolant in the oil (or oil in the coolant). It is simple enough to do and would assure you the problem is not a head gasket or sleeve failure.

At engine temperture higher than about 215F BOTH radiator fans should be running at full speed without the air on. If they are not, this is the bulk of your problem.

Coolant tank has nice yellow stuff in it and Oil dipstick and oil fill tube have no signs of milky stuff just nice golden brown oil.

if it was that lean it would have a check engine light Really need a tester to verify that the fans are running properly I would be checking that the t stat is working properly and then if all checks out pull thewater pump to verify that the impeller isnt loose or damaged

went for a drive and got it warmed up... when the temp hits 102/103C the high speed fans kick on just like they are supposed to. Guess I am past the easy checks and into the difficult area... thermostat, water pump, etc. thanks for the ideas.

I guess its time i start loking into the other things. Im running at streets again this weekend so I know temperature will be a problem.

spray the radiators with citrus cleaner and spray it down whith a garden hose. This will ensure air flow through the radiators...my .02 cents.

If your coolant temp is getting that high, that fast, you probably have a flow restriction. As suggested earlier, test the system to make sure it is flowing properly. Waterpump may be worn, partial opening of theromostat or other blockage. Have you ever flushed the system?

My next guess

you can check the emmisions throughout the coolant reservoir. If you see lots of ppm, then there are some bad news. Its head gasket failure

Yellow? Porsche coolant is pink...

No....not universally pink. I had mine repalced by Porsche when I bought it and the coolant is also a yellowish sor of color. Iv'e been running this coolant for over a year since I bought the car.

Cool. I figured it was worth pointing out... it wouldn't be the first time I'd heard of someone putting the wrong coolant in a car or, worse, mixing types. I'd recently bought a jug of Porsche coolant, and it wuddint yellow.

CHuck - there was a thread a while back that discussed the yellow vs. pink Porsche coolant. IIRC, the pink is the latest version of the Porsche coolant.

Unfortunately, it doesn't seem to make a damn bit of difference...they charge you $45 a gallon no matter if it's yellowish or pink. I read somewhere that you can buy it chaper from the Volkswagon folks? You'd think they'd use the same stuff...yes/no??

Porsche yellow coolant and Porsche pink coolant CAN be mixed. Other coolants can not. http://www.renntech.org/forums/index...ndpost&p=56360

I know this has been talked about before, but can someone tell me how I check the coolant temp via the climate control screen? Thanks

I think this is the process...if it will load here...hope this helps....Chuck: Porsche Boxster AC Diagnostics (undocumented, unsupported feature) The AC Climatronic unit is actually manufactured by Audi. There is some sort of serial data stream (not CAN) that allows the AC unit to display engine parameters. This works on 1997-2000 boxsters. To switch from F to C: Hold down the recirculating button then push both the temperature + - buttons. To access diagnostics: Hold down the Recirculating & Air up buttons for 5 seconds. The + - buttons go up and down through the list of "c" codes. The center vent button switches the left display between the "c" code and its actual value. Press the Auto button to exit. I have yet to verify all these, this info was copied from wonderful people on PPBB! Here is a list of what can be seen: 0c - ERL 1c - Oil Temp? 2c - Inside temp. Sensor mounted in the aspirator assembly at the side of the dash. 3c - Outside temp. Sensor located inside the air inlet of the A/C unit. 4c - Outside temp. Sensor located in front grill of the radiator. The data is fed to the Climatronic from the instrument cluster. When not moving, the instrument cluster OBC temp display retains it's last setting until moving. This is to prevent heat emanating from the radiator affecting the temperature sensor. The A/C unit uses the lower of the two outside air temp values in determining fresh-air temp. 5c - Outside temp. (matches with OBC outside temp display) 6c - Coolant temp. 7c - Footwell discharge temp. 8c - Sun sensor (dash top) 9c - Sun sensor. 10c - Passenger compartment fan speed. 11c - Passenger compartment fan voltage. 12c - Temperature mix Flap command 1=COLD, 100=HOT 13c - Temperature mix Flap position 14c - Central Flap command 15c - Central Flap position 16c - Footwell/Defrost Flap command 17c - Footwell/Defrost Flap position 18c - Recirculation Valve command 1=OFF, 100=RECIRC 19c - Recirculation Valve position (feedback) 20c - Vehicle speed in kph, updating only once per second. (real speed, not speed+safety margin as in the speedometer) 21c - Engine RPM in hundreds. This too only updates once per second. 22c - ? 23c - ? 24c - Sun sensor, exterior lights switch & panel lights control (term. 58 & 58d voltage) - used for A/C panel display illum. 25c - ? 26c - ? 27c - ? 28c - Fan speed? 29c - ? 30c - Engine run time in seconds (255 max.)(=0xff) 31c - Timing counter 32c - Displays test 33c - Software version? Mine states 3.4 34c - ? 35c - Outside temp. from inlet sensor (filtered?) 36c - temp?

tried this on a 2002 986, and it didn't work.

+1 at speed, on the track, air fed into the radiators will provide more air than a fan ever will. fans are good for stop and go driving. i would suggest getting the mk1 gt3 bumper (or similar) that would scoop even more air into the radiators. you can also try straight water (no anitfreeze) and water wetter. this proves better cooling than a 50/50 antifreeze mix.

Thanks Chuck, tremendous post......

The stock bumper AND the GT3 bumper do not allow more air to the radiators than the fans will force through for speeds under 60 mph. If you are a serious tracker, why do you still have the A/C in the car? Removing the condensers will greatly improve airflow for cooling.

i've tried it on my '99 996 and it works.

yup, removed my ac condensers. actually, the gt3 mk1 bumper is wind tunnel tested and said to flow more air into the radiators than stock. i would agree with you up to speeds of 30 mph but not 60mph. try this... stick your hand out of the window at 60 mph. note the force it takes to hold your hand against the. now stick your hand under fan/radiator exhaust port when the fans are on high. same force? nope! the fan is pushing less CFMs than rushing air would. it's a simple experiment but very telling.

I have the GT3 bumper (on 2 cars) and have tested the cooling effect extensively. Running the fans n high at speeds under 60 mph will ALWAYS provide more airflow past the radiators. You willl ALWAYS get cooler coolant temperatures with the fans running under 60 mph. Proof is in the reduction of coolant temps.

As far as I know these only work on MY01 (some) and older cars. Real credit goes to the Audi folks that documented all of these codes here .

At what temp are the fans activated? My commute is 35 miles on all curvy country roads . My temperature stays just right of the 180 degree mark...and I mean just right, it almost touches it. I'm averaging 70+ mph. I stopped today to open my bleed valve and the fan wasn't on. Should it be on at just above 180 degrees? Mine's a '99 996.

Just an update, Car is at the shop. Water pump is good, Thermostat is good, and coolant is good. I guess I have to accept my only option for tracking a car in southern California is the third radiator. Unfortunately, suncoast says about 4 weeks to get me one so I need to check the other places to get it.

Just a note: Unless they have the capabilty of accurately measuring the flow of coolant, there is no way they can determine that the thermostat has openned all the way and they cannot determine if the water pump is good or not. Due to improper engineering the 3.4 water pump and thermostat restricts the coolant flow to much. This has been partially corrected in the 997's. Because of this restiction, removing the thermostat can reduce coolant temps at speed by as much as 5%. Removing the thermostat is a simple, quick job. This is contrary to some engines where removing the thermostat will increase flow too much, not allowing the coolant enough time to cool while passing through the radiator.

1999 Im realy curious to see your thermal enginering degree

Rather than looking for qualifications to make my statement, let's hear why you think I am wrong. I made a vary simple, clear, factual statement. If you think it is wrong, please provide us with your opinion.

Im just curious how you can make statements of "Because of this restiction, removing the thermostat can reduce coolant temps at speed by as much as 5%. " Id like to know the extent of your research where you found a 5 % reduction and what qualifiys you to perform such research

Because it does? Actual testing is always a better indicator than text book theories. There is an optimum flow rate and pressure in a cooling system necessary to acheive cooling effeciency. In 95F ambient temperatures, the 3.4 engine will run as much as 5% cooler at highway speed when the flow of the coolant is increased by removing the thermostat. The effect on coolant temperatures around town with fans running on high is currently being tested, but preliminary results are that coolant temperatures will also be lower. An engine's thermostat plays no part in coolant temperature once it has reached opening temperature. Installing a 150F thermostat in place of the stock 182F one will not decrease or increase coolant temps. What can effect the coolant temperature is the restriction in flow caused by the thermostat. Too little restriction and temperatures will increase. Too much flow and temperatures will increase. You must find the optimum flow rate which will allow enough coolant flow through the engine to absorb the heat as well as the correct flow that will allow the coolant to pass through the radiators slow enough for cooling to take place. It was common practice when building race engines to oversize the water pump and find it's best efficency by introducing various size washers in the outlet until the best effects were acheived.

i understand that but by giving a percntage implies that you have flow tetsed a 3.4 engine and have found that you increased cooling capicty by 5%

It DOES NOT mean that. It stated that the coolant temperature is 5% less. I gave no percentage increase in coolant flow. I have no idea where you are getting that from.

My car just depends on the temp outside. Since we have been experiencing this monsoon season and temps have below 90-100 my car has been running at perfect temperatures. I have found that its once the temp outside reaches > 105 degrees, I start running higher!

Without knowing where the 'factual statement' is coming from, it's hard to see it as a fact, and 'prove me wrong' isn't a defense. I've always been curious about why you know so much about this stuff, too. You're very convincing, no question, but the things you say makes folks think they bought badly engineered cars and have to go out and spend a bunch of money to correct them. Given those strong statements, I don't think it's unreasonable to ask why you're so confident.

I'd like to bump this up and maybe back-up just a second to ask a simple question. I ran this weekend on a 95 degree humid day here and was paranoid about temps. Every car I've ever owned has a dummy guage in it to where once the guage moves past the 1/2 way mark it's usually already too late because the car is VERY hot. It seems as though the Porsche guage is fairly accurate so my question is how hot is too hot for our cars. My car in standard driving usually has the needle disecting the "0" in 180 or on hot days is just to the right of the 180 mark on the guage. BUT at this position it appears as though the car is regularly running in the 200-210 range anyhow. If the lines on the guage are at regular intervals than the marking between the 180 and 250 would be around 225 degrees. After 5 or so hard laps at the track my neeedle would pass the 225 mark at which point I backed off and let the car cool down. I never got the light to illuminate but it doesn't appear to go on until 250 which seems awefully high for a dummy light if you ask me. So...how hot is too hot to regularly run the 996? Is 225 safe? It seems like it's only slightly higher than what the car normally operates at? The third radiator seems like a very good idea after this past weekened for peace of mind..just curious where we should I should start to get concerned with temps though? Andy

Agree your comment about the gage. Having actual gages really seems to make some folks obsessive about this. Without answering your question, a couple of useful things: It looks like you have a mark 1 996. They always seem to run hotter because the gage takes its reading from only one spot in the system, back in the engine. The later cars average the reading between two places, there and at the rad, I believe. So calibrate the advice you get by the version of car the giver drives. You can confirm your operating temp via the OBD, using a combination of buttons on the climate control. Do a search for that. (Sorry I don't have it, but I'm not at home). Some will tell you that your dash gage reads lower than the true temp. Maybe so. In my case, the gage and the OBD readout agree. From what I've been able to gather, if you track your car it's worth the third rad. Regardless of whether the operating temp is 'okay' or not, the fact is that the car will lose power when it's running hot anyway. And what would the point of that be when you're racing? Good luck with your search.

Also remember that the fans come on later in the game on P cars than other models. There is also a fan switch mod to activate the fans earlier if need be. The first thing that will go out will be the AC. The computer will automatically shut this off when heat increases beyond managable level. And this is very high. Afterwards you will see the light from the compartment being too hot, then........... I dont want to see what then is.....