Engine running hot...

I know the 996 cooling system can sometimes be a little overtaxed, especially on hot days in traffic. However, this seems to be occurring more frequently. I was recently stuck in bumper to bumper traffic on I-70 on a hot day (90 degrees F, nothing too crazy) and I watched the temperature needle slowly make the journey up towards the red line at 250 degrees. It eventually got there, and I had to pull over and shut the car down to cool for a while. Typically this car runs with the temperature needle right between the 8 and the 0 at 180 degrees. When I sit in traffic now, it gets well beyond that, usually to the line between 180 and 250. My coolant level looks good and I've recently cleaned my radiators. Is this something that should concern me? Is this potentially a failing water pump, thermostat or other issue with the cooling system, or is this just normal for a 996 in hot weather? I don't really remember this issue in the past. Also, when the engine gets hot, the air conditioning system doesn't work well. I'm not really surprised by this one, but it's certainly not pleasant sitting in traffic on a hot day with the engine getting hot and the air conditioning now working well.

Have you checked the radiator fans to be sure they are working properly? It sounds like the heat isn't being bled away efficiently if it is a gradual rise while sitting in traffic.

Do you have the third radiator? I have seen my needle creep to the end of the 0, in similar weather/traffic. It helps to have the A/C fan on high and the temp at the lowest setting; I can hear the front fans turning on right away, and it drops the needle quite a bit. I also raise the rear spoiler electronically, IDK if it helps, but it does open up the area for the heat to escape, IMO.

Shouldn't get that high. 250 is not good. A little to the right of 180 is ok, but not too much farther. VERY LOUD stage 2 fans up front should kick on at around 212F and stay on until it gets down to 205F IIRC (the gauge it is not completely representative of the actual temp) and lower the temperature. Engine compartment purge fan should kick on when it gets REALLY hot. Simple test, turn your A/C off. Roll you window down. Turn the A/C on, you should hear stage 1 come on (low speed). It is possible one or both of your fans or ballasts are not working, or there are other problems. If you have Durametric you can activate stage 1 or stage 2 with the car off to inspect the operation of both fans.

As others have said, this is definitely not normal. Step one is confirming the fans are working properly. My guess is that one of them isn't working properly due to ballast, fuse, or general failure. -Shawn

I can hear the fans kick on, but I haven't paid attention to exactly when they come on and when they are off. I did notice the other day that after I drove the car, parked in the garage and shut the engine off, one of the fans was still running for a while. I don't have the 3rd radiator in my car.

One thought is you might make sure you didn't knock some fan wires loose when you cleaned your radiators, if that's about the time the problem showed up.

First make sure that the low and high speed fans are coming on at the right time. Don't let it get that hot again because you are asking for a cracked cylinder head. Anything past the "0" in 180 is way too hot IMO. Water pump could be going bad - not moving enough coolant at idle do to a failing bearing or broken impellers. First check the fans because that is what it sounds like. With a new OEM water pump, the LN 160 degree stat, a few new hoses in the engine compartment, and 2 fresh gallons of coolant/water mix, the needle in my car never moves past the left side of the "0" in 180, this is true even sitting in bumper to bumper traffic in 90degree+ heat.

Just wire a switch to turn on the fans in high and switch it on while you are in traffic...

Dennis, did you get a specific reading by using the celsious temperature display in the center panel or an estimate on the temp. guage? GL

It was a temp gauge estimate. I don't think you can use the display on MK II cars the way that you can on MK I cars.

I just spoke with my mechanic and described the symptoms. He's quite confident that it's the fan relay based on our discussion. I was planning to head down the hill to pick up the Cayenne this afternoon, so I guess I'll pick one up and drop one off.

Quotes source post: 8691390

If one or both fans are not working properly that needs to be addressed, to say the least. However, I drove my 03 Turbo through some pretty warm temps (90F+) (from Fresno CA north to Tracy then to Livermore) and with the A/C on no less with only one working radiator fan and while the coolant needle edged a bit higher than normal (maybe a needle width if that much) past the 180 mark I couldn't have known the fan was not working had I not felt for air flow at both radiator duct openings and noticed no air flow at the passenger's duct. A slight change in the noise when the fans (or fan) came on prompted to me to get out and check. Also, I drove my 02 Boxster through 116F heat in AZ one day a few years ago and the coolant temp (viewed using an OBD2 code reader/data viewer) reached 226F and stayed there and intake air temp was in the 130F (again viewed using the OBD2 code reader/data viewer) and a bit higher range. Furthermore, while I was driving on the freeway most of the time and at freeway speeds (70/75mph) every time I left the freeway and slowed down I could hear the engine compartment fan running. While the temp gage needle climbed to areas I had never seen it climb to before there were no other symptoms. When I got back home I checked in with my dealer's service department manager, gave him the numbers, and he contacted the factory. The factory's response was as long as the coolant light was not on or flashing there was no overheating condition and no harm to the engine. That was years ago and over 100K miles ago and apparently the factory was right. In your car's case, while that needle reaching the higher temp area of the gage the coolant temp is probably not 250F but closer to well 226F. My info is (though there is some disagreement from various sources of this info) is the fans come on low speed when the coolant temp reaches 212F and shut off when the coolant temp drops to 205F. If the coolant temp continues to climb past 216F the fans switch to high speed and stay on high until the coolant temp drops to 205F. As long as the warning lights didn't come on, the coolant level is ok and the system is pressure tight (which is critical because it is the pressure that prevents the coolant from boiling not the anti-freeze) then the car's cooling system is ok. But of course if any fan is not working right either doesn't come on low speed when it should or doesn't switch to high speed when it should or doesn't come on at all, the cause needs to be addressed. While these cars have some cooling margin (considerable based on my experience) one should keep both fans working. I aborted a trip east with my Turbo when I found the one fan not working because I had no desire to risk a long drive across very hot territory (the southwest) in a car with just one working radiator fan. Sincerely, Macster.

My radiator fans have been running all Summer long. Maybe not at highway speeds (I can't hear them on or off at speed), but certainly while the car is sitting in traffic. Temp guage hasn't gone much above 180, so I'm not sure 212 degrees is what triggers them. I guess my guage could be off, but it's pretty consistent at hovering around 180 regardless of the ambient temps or speed of the car. The only time my rear deck fan comes on is after I turn off the car on a hot day. It comes on about a minute after I turn the car off and runs for a few minutes.

The fact that you only heard one fan running in the garage is confirmation that you have a problem with at least one fan. Both fans always work in parallel. There's never a time when one runs and the other doesn't when things are in good working order. -Shawn

I would start at the fans as well, I've seen many of them inoperative.

I recently replaced the left (front) radiator assembly after a blown fuse and a burnt-out fan motor. A fairly easy DIY. Found cheap new parts on fleabay (comes with the thermistor): http://cgi.ebay.com/ebaymotors/ws/eB...K%3AMEWNX%3AIT In current hot Houston weather I am also running the hack to keep the fans running at high speed: http://www.ppbb.com/phorum/read.php?6,1509504,1509504

[QUOTE=SSST;8691730]My radiator fans have been running all Summer long. Maybe not at highway speeds (I can't hear them on or off at speed), but certainly while the car is sitting in traffic. Temp guage hasn't gone much above 180, so I'm not sure 212 degrees is what triggers them. I guess my guage could be off, but it's pretty consistent at hovering around 180 regardless of the ambient temps or speed of the car. The fans come on at low speed whenever the A/C is switched on. That's why you're hearing them before your temp gets to 212 degrees.

Quotes source post: 8691730

[quote=Down South;8691967] Correct. And my observation is this helps to keep the coolant temp more stable and lower than it would be otherwise. On a mild day, mid 70's, and in stop/go driving I have observed (and data logged this) my Boxster's coolant temp climbing to the point the fans come on. The fans run and the coolant temp drops and then the fans shut off the process repeats. Even in warmer temps though with the A/C on the fans of course run all the time with the result the coolant temp stays relative stable and way under 212F. By 'way under' under highest I've seen it get (save that time in AZ) is about 205F. Sincerely, Macster.

Well, it's already at the mechanic. I'll keep you all posted tomorrow when I get the final diagnosis. He feels pretty certain that it's the fan relay. When I told him about the issue his first question was: "does your air conditioning work poorly when the temperature gauge starts to rise?". His assumption was correct - the air conditioning doesn't work well when the car gets hot. He believes that one fan is working which is marginally enough to keep the car from overhearing, and the other one is not coming on, so the engine doesn't cool properly and the a/c doesn't work properly.

Ivangene might be able to help get more air cooling effect for it

Dennis, A couple of thoughts (1) I highly recommend the LN 160F thermostat. I find that the car runs cooler on the highway and will cool more quickly once it gets hot. (2) The manual fan control "hack" has been great as well. When the car get to 200F + I can turn it on and actually watch the car cool to 190F while sitting still as it turns on the high speed fans.

+1 on checking the fans.... Im not buying that coolant is a lifetime in these cars. Worse case try a flush with new Porsche coolants.

Just an observation I've seen a lot of suggestions above for improvements to the cooling system which is great. But I would be afraid to start throwing parts at this without troubleshooting the root cause. The bottom line is 250F and overheating is not normal. Perhaps there is air in the system, low coolant level, your fans are not working, or you have a sensor problem. It sounds like you have the car at a good shop. Also, did you test the coolant with a hydrometer?

I just heard back from the shop. It turns out that the fan wiring and relays are good, however both fans are defective. One isn't working at all and one isn't working properly. Both are being replaced.

Glad the shop got to the bottom of the problem before serious damage to the engine.

Glad to hear that your overheating issue will soon be resolved.

if the fan wires and relays were fine, what was defective specifically with the fans that they wouldn't operate properly?

I'll ask when I pick up the car tomorrow, but I believe that the fan motors were bad.

I hope that takes care of your problem and nothing else is found!

I check my fans in the summer. Turn the AC on and it fires up to low. I turn the fan mod switch and it kicks up to high. The radiators were cleaned beginning of last summer and the fans cool the engine down quickly. 5,000 miles and one year later, it doesn't cool as fast and the temp is also a few degrees C higher on a hot day. Cleaning the radiators is very important from this observation...

Quotes source post: 8693631

Wiring and relays are the most common reasons why the radiator fan stops working. Porsche techs tell me they often find a car that comes in that has had front end work/repairs that involve the A/C condensor and radiator with misrouted wiring even to the point of finding the relay has been jammed in between some plastic panels. The relay runs hot so this is not good. It should be properly mounted to receive cool air and to avoid flopping about which can cause the wiring to fail from fatigue. Now in my Boxster's case a relay was found bad and the front end while it had been worked on a long time ago (at the Wichita KS Porsche dealership service department) had everything routed properly the tech believed that the relay just reached the end of its life. BTW, the non-functioning radiator fan motor was on the passenger side (which was not the side the dealer worked on though) but in the USA it is the passenger side that is often subjected to heavier and more frequent water splashes. In the case of the Turbo while the front end the passenger side had been worked on all the work was done at a Porsche dealer. Furthermore, I had the work inspected at another dealer by a senior tech there to confirm the work was done right -- I had the bumper cover removed and the work inspected very closely by this tech at the 2nd dealership -- the fan was not working because the radiator fan motor's shaft snapped. In snapping the hub/fan assembly banged into the back of the radiator. While this didn't hole the radiator it damaged it (bent some fins over) nonetheless and both the radiator and the fan/motor assembly were replaced under CPO warranty. The tech told me he had never seen a radiator fan/motor shaft snap before. Oh, before the reason the Turbo's passenger fan was not working was determined I asked about the relay and water splash and the tech took the time to point out where the relay was located and it was located correctly (of course, for it was he that had inspected it before and pronounced the routing and in fact all the work done under the front bumper cover of the Turbo correct and 'factory') and in a quite protected area, nowhere near as exposed to the elements as the relay in the Boxster. Sincerely, Macster.

I've been getting a ENGINE COMPARTMENT BLOWER FAN warning light in my 996 GT3 intermittently at the track, but when I pull into the pits, the engine compartment fan is blowing. Can this warning light be related to front radiator fans?

The car is back now and in good working order. It has two new fans and two new fan relays. According to the tech, the fans were simply worn out. He said that both fans were inoperative when power was applied directly to them. He told me that this isn't as common as a bad relay, but in a car with over 100K on the clock, it's not unheard of.

Quotes source post: 8696075

The warning light on signals there's a problem with the engine compartment fan. While I'm no expert, and you really should consult with one to be safe, I do not think this warning light has anything to do with the radiator fans. Their functionality is monitored so to speak by the coolant temp gage and the engine coolant warning light. That is if anything was wrong with the fans you'd know it from the coolant gage and if seriously wrong from the warning light. (You should always before a track event check that both radiator fans are running before you head out and when you come in after a cooldown lap verify the fans are still working ok.) The fan is running so the fan and its wiring circuitry (including the fuse in the fuse panel) appear to be ok. I'm not sure -- I've never had any reason to dig into this area of any of my Porsches -- but my WAG is the problem is related to a temp sensor that is located in that general area. It is this sensor's output (fed to the DME) which is used to monitor engine compartment air temp and this sensor's reading is used to control the fan, to turn it on when teh temp gets too high and to turn the fan off when the air temp drops to an acceptable level. The temp sensor may be loose or going bad. The engine compartment fan plays a critical role in keeping engine compartment temperature down and the lower the heat the less heat damage the components in the engine compartment experience, so my advice would be to take the car to an expert and have this looked into and get to the bottom of the cause of the blinking light. Sincerely, Macster.

What about setting the pin up on the bleed valve to bypass the thermostat? There's been a bit of discussion here . This provides us with a cheaper (free) option compared to paying $$ to fit in a new thermostat.

Quotes source post: 8701619

I do not know of any way to bypass the T-stat. The T-stat should not be bypassed anyhow. The coolant's resistance to boiling is primarily derived from the pressure the cooling system builds when the cooling system gets hot, up to temperature hot. If the cooling system can't hold pressure due to a water pump leaking or any other leak in the cooling system the leak should be found and fixed. Opening some pressure bypass/relief valve on top of the coolant resevior tank simply creates an even larger pressure leak which under some operating conditions can allow localized overheating to occur with risk of serious engine troubles this brings with it. Sincerely, Macster.