Radiator Fan and overheating

[RandallNeighbour]

If you owners of older boxsters have noticed that your temp needle passes that second white line to the right of the numbers (180) when you are sitting in traffic in the summer heat, you may want to check two things:

1) Take a flashlight (torch for you Brits) and peer into the air ducts in your front bumper. Is there a pile of leaves and debris stacked up against either radiator? If so, you need to remove it with a shop vac and a long, thin attachment. Then, when the engine is cold, take your garden hose and a sprayer attachment and blast the radiators good to knock off any dirt or dust that has accumulated. We should all do this every six months or a year just as a PM item.

2) If you still experience some mild overheating problems, then you need to do a simple test to see if both fans are functioning. With the car hot and running, put your hand in front of the front wheels below the bumper and see if it's blowing hot air downward on both sides. If I am not mistaken, the driver's side is fan 1 and the passenger side is fan 2, so the driver's side should certainly be on if the engine is hot.

3) If one of the fans is not on, you need to have it tested with a PST tool, found at dealerships and mechanics who work on Porsches. Mine did this last night and found that fan 1 was out.

4) There are two main things that make the fan work. The fan itself and a resistor. My mechanic tells me that the resistors often go out and the fans are fine. If it's just the resistor, the test on the PST tool will activate the fan because it bypasses the resistor. If the PST tool can't start the fan, the fan may be out as well. The "stealership" service dept. usually quotes that the fan has gone out and hits you for a fan and resistor when you take it in for this problem. Retail on the fan is $335 and the retail on the resistor is $52. Of course, Sunset has them far cheaper and you should buy stuff there if you use an independent mechanic and supply your own parts or you do the work yourself.

Why tell you all this? I just decided to start posting everything I discover about my old Boxster when it happens to me so others can have a heads up in advance and not become so freaked out over what could be wrong. Even expensive or bad news is easier to anticipate when we have some information.

If anyone has any contrary info on this (I got something wrong) or has additional info to add to this thread, please do so. I always learn so much from everyone here.

[Brucelee]

Randall,

Good info. Personally, I have found that the location invites debris etc. Getting down there to clean it out is a good thing!

Also, generally, I can hear the fans running if I am in front of the car (and not driving it of course!).

[deliriousga]

Much cheaper relay:
If the "resistor" your mechanic referred to is the relay, then you can get it at Radio Shack for $7. Take the old one with you and match it (there is a switching diagram on the top of the relay). It's a simple, very common relay. If you really want one that's from Porsche, get it at one of the "big 3" 928 parts sellers for $12. The part number is 141 951 253 B www.928intl.com www.928gt.com www.devek.net Get a few for future problems. There are 8-10 of this relay in the Boxster so you will use them some day.

Another way for fans to fail:
As for the fan going out, there can be other things that cause the problem too, but it would be different from Randall's problem with both fans going out rather than just one. If the coolant temp sensor isn't working properly and does not read an operating temp condition, it will not signal the fans to come on.

Keep it on the road:
One thing I did with the rear fan that I will be doing soon with the front ones was to put a manual override switch in. I did this with the rear fan because the engine compartment temp switch died. It's a week wait for the part so I bypassed it until it gets here so the fan is on when the car is on. I put waterproof clips on so I can leave the switch in and just reconnect the fan to the system when I get the part and put it in. Then if I ever have a fan failure while I'm out somewhere, I can just clip the override switch in and turn the fan on as long as it's not the fan itself that has failed.

Debris in the front ducts:
Like Randall said, it's a great idea to clean it out, but there are other problems with the ducts you may want to head off. My PO had a rock go straight through the ducts and wack the A/C compressor killing it. PCNA replaced it, but the dealership's mechanic said he had seen several Boxsters have the same problem and suggested covers that would block big rocks but still allow the airflow. He put them on and I have not had any problems. They also keep the big leaves, etc. out so there's not much cleaning.

[mdimant]

Hi Randall, I have read your posts b4 & you sound quite savvy without being a know it all! I have a 2k Box S & after some intake & exhaust improvements that are very satisfying, I have installed a 160 t-stat and would like to lower the aux fan limits to compliment ths stat as the car runs much better in the warm up phase than at the stock op temp, which I understand is set to assist in EPA compliance. It runs nicely & stays @ the '1' of 180 until I drive it agressively, and it heats up a bit because the fans are not set to help till 210 or so. These temp gauges suck if you ask me & they seem designed to have you think the car is not as hot as it really is! I don't care if the heater is'nt real hot, but when the needle is just on the right side of the '0' of 180 I beleive it to be about 210. From everything I have read on the lower op temps, it is beneficial in all aspects accept mileage, which I don't care much about. These are not gas hogs for the performance they offer. Where or how would you suggest I address this sensor/relay issue to get aux fans in allignment with the stat? I want the fans on @ 180+-. BTW, the stat is a Hypertech #1014 for a '97-02 Vette. Thanks man! Martin 253-514-9002 mdimant@comcast.net