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Registered User
Join Date: Aug 2019
Posts: 2
Boxster 987 2.7 overheating - radiator fans only run when AC is on

Hi, got an interesting problem which I have been having for a while.

My '06 987 is in great shape - only covered 100k kms - but occasionally overheats running around town as the radiator fans never turn on no matter how hot the engine gets.

The way I try to avoid this is to put the AC on, which gets the fans spinning.

So basically I know the fans are good (and I assume the wiring too) but what I can't work out is what sends the signal to the fans to get them to operate?

The temp gauge arrow sits vertically during normal running and it is only when I stop at the lights and notice a pool of fluid running out near my right rear wheel that I know I have a problem.

I am assuming the temp sensor must be sending out the correct signals if my gauge is working ok. I tried shorting out the temp sensor wires (to simulate a hot fluid situation) but the radiator fans still won't operate.

In addition, whenever I start my car after it has been sitting for ten minutes after switching it off, the engine compartment fan will run continuously for around 15 minutes of driving. My understanding is that the 987 radiator fans should continue operating when the engine is shut down, and the fluid is above a certain temperature, in order to cool the hot engine down to a set temp.

Any thoughts or suggestions on where I can start the diagnostic process will be much appreciated.
Old 08-29-2019, 04:57 PM
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Join Date: Aug 2019
Posts: 2
Ok, had a Solus scan done today.

Messages say
1. The thermostat is stuck open - I thought this would actually help with cooling as full fluid flow through the thermostat is guaranteed; and
2. The temp sensor is both exceeding the limit value and is below the limit value (2 separate messages).

I guess the first thing to try is a new temp sensor so I'll see how that goes.
Old 08-31-2019, 11:16 PM
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racer's Avatar
Join Date: Jan 2004
Location: Northern Virginia
Posts: 3,081
Sounds like just a bad fan switch at the unit? Thus, only when you run the AC and get its condenser fan running do you get any cooling.

While your in there (front bumper cap removed) be sure to clean out all the road debris that collects down those cooling openings!

if the switch is open, you are merely giving the coolant a longer passage, but its not inherantly cooler. Getting the fan to turn on to blow air over the radiator is key.
1970 914-6
2000 Boxster 2.7, 1987 944
1978 911SC, 1976 914 2.0, 1970 914 w/2056
Old 09-03-2019, 05:19 AM
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Brian Minson's Avatar
Join Date: May 2016
Location: Gilbert, Arizona
Posts: 77
Have you checked the relays under the dash yet? And do you have the most current "blue" coolant cap installed?

Old 09-03-2019, 08:42 AM
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987 , overheating , radiator fans

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