Ahmet

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

flyingpenguin

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

Down South

[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.

Macster

[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.

Dennis C

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.

Pac996

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

fbgh2o

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.

redridge

+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.

logray

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?

Dennis C

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.

Kazual99

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

Barn996

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

Topaz330ci

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

Dennis C

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

Down South

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