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.

 

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