I have had some cooling issues with my 986 in the past. They have mostly been resolved since I did a complete coolant flush at 95,000 miles, replaced the water pump and installed a low temp thermostat, 'S' oil cooler, and third radiator. I believe these issues originated from an independent mechanic I used to go to that may have mixed two types of coolant which can cause them to gel.
While driving with the top down this summer, I was consistently hitting the 210 mark on the coolant temp gauge, when it should max out near the 0 in 180. then while stuck in traffic I passed 210, and had to pull over for my 986 to cool down. The cooling system worked fine on the freeway when air was getting rammed into the radiators. After some testing, I determined that my driver's side radiator fan had died.
Here is the process for diagnosing the radiator fans:
-Check the Fuses, Row C, Slot 8 & 10
-Check the Low Speed Relays, #19 & #21
-Check the High Speed Relays #20 & 22
You can test the relays by placing a finger on them and feeling for them to "click." The low speed relays should trigger when the AC is activated. To test the high speed fans you need to manually ground pin 85 of the relay or use a Durametric tool.
If the fans run on high, but not on low, it is likely the fan resistor, which is a common failure. If neither the high or low speed works the fan motor is likely dead. Some people have used generic resistors to more cheaply replace the resistor, however if you want to use an OEM Bosch part it isn't much more to just replace the entire fan assembly which comes with the resistor.
If you want to test the fan motor and completely bypass the relays, you can jumper pins 30 and 87 on the relay panel with a wire.
In my case the entire fan was dead, so I bought the entire assembly from Bosch who is an OEM supplier to Porsche. By using the Bosch part number (#0130303233) I paid $175, versus $500 for the same Bosch part in a Porsche box from a dealer.
The Bentley Manual details the fan replacement process and Pedro's Garage also has a step-by-step DIY guide. Luckily, replacing the fan does not require removing the front bumper, which can be a PITA, the fan can be accessed from the wheel well.
It took me three hours from start to finish to replace the fan. I disconnected the battery and put the front of the car on stands, with the rear wheels chocked, then removed the driver's side wheel. The Bentley Manual tells you to completely remove the wheel well liner, however if you disconnect the front, it is flexible enough to just be bent back behind the rotor and it doesn't interfere.
The hardest part was getting the bumper strut off and back on, I used a screwdriver as a lever to get it off, and a hammer to get it back on. The only thing you need to be careful of is making sure the fan shroud is back in place properly when reassembling, mine got caught on the plastic fan housing and I had to use a stick to get it around the housing. Also note, that the fan shroud stays attached to the radiator support bracket you remove, I tried to disconnect it, but it isn't necessary. The rest of the replacement is fairly straightforward.
I reconnected the battery and tested the fan before reinstalling the fan shroud and radiator support bracket.
Overall, this repair cost me $175 for the fan, $15 for two day shipping, and three hours of my time. I already had all the tools, which didn't include anything exotic. Basically 10mm and 13mm sockets and/or wrenches, a couple of screwdrivers (including torx), pliers, and a hammer/mallet.
Replacing the fan solved my overheating issue. It's amazing that one fan can cause the engine temps to spike so much.
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