update on overheating- now what?

[jhandy]

Thanks to all the guys that helped out, I cleaned the radiators, they had a lot of junk in there.

I started the car with AC on, Both fans are running. AC off, both fan turn off.
Temp 198.

Then I went for a drive, It is hot outside and I drove max 25 miles an hour around the neighborhood.- AC on the temp went to 205.

Then I turned the AC off, and the temp went to 211!!!!

Stopped the car, let it run, AC off, the engine fan turned on, BOTH FANS UP FRONT ARE OFF, temp went to 217, no light on dash.

I turned it off and now I am worried. I always have the AC on, so the fans where always running, and it never went this high. With no fans, I bet it would overheat.

Whats going on? Are the fans supposed to turn on? At what temp? I guess the sensor may be out....where would that be?

James

[jhandy]

Also,
Why is there not a center radiator fan?
What harm would it be to have the fans running all the time? Replacement fans are 150$- engine- 15000$.

james

[blinkwatt]

I know this wouldn't be a long term fix but couldn't you install a manual switch for the radiator fans and turn them on when the needle is about to hit the '0' on '180'?

[jhandy]

Well that is what i was thinking. i was just going to wire it up to turn in when the car is running.
also i wanted to add another fan the the center. The needle looks fine, It always goes to where it is currently, never has had the light turn in. I think that the only reason i notice this now is due the scangague hooked to the obdII port. I bet a lot of people are hitting 210 and more.

[cnavarro]

At speed, the fans don't need to be run. In fact, I'm pretty sure on a spec Boxster, they remove the fans. At low speeds or stopped, having the fans run will help, and in fact, with the a/c on, at least the passenger fan is always on. I made the same observation that the temp would rise when the a/c was shut off at a stand-still because you're eliminating the last bit of airflow over the radiator. Theoretically, setrab does make some very small fan packs that would fit nicely on the 3rd (center) radiator to help with low speed/ low airflow scenarios.

The fans typically don't turn on until 210F, or at least that's what I observed in my car. I agree, this is too late. I would prefer they came on much earlier.

[Lil bastard]

Sounds like an electronic issue - Fuses (C8 - Rht, C10 - Lft), a relay (there are 4 Hi/Lo speeds, Lft, Rht - #19, 20, 21 & 22), or the Series Ballast Resistor(s) PN# 996.616.101.00.

The easiest is to check the fuses and relays, though I'm betting on the resistor. If you still haven't removed and cleaned the radiators, here's your chance. The resistor is located in the wiring narness to the fans and you just splice a new one in. The fans will work w/ AC on because that is a high speed operation.

The one thing you need to do is get in there and see what's going on. It's possible that some debris has damamged the wiring or resistor, and they are a known weak point, such as the thermo-switch was on older brit cars.

Charles is right that the fans are moot once the car is going 35mph. At this speed, more air is forced through the radiator vanes than the fans can draw through. In fact, the fan blades actually become restrictive reducing the flow that would otherwise take place, though there remains enough to do the job.

If all else fails, the final component is the DME because this is what actually activates the fans. This failure does not throw a CEL but would be seen with a PIWIS or PST2 tester.

[jhandy]

ok, Sounds strait forward. The car stays at 195-198 at highway speeds and shoots up when driving slow.

How do I test/check the relays? Do I have to go buy new ones and see if that works or can I bypass them electrically and take them out of the loop?

as for the resistor, pretty much the same question. How do I know that it is bad? I did a quick code check and nothing came up...I just want to avoid going to the dealer (50 miles away) and start buying things that are not needed.

I just cleaned the radiators, I did not remove them. I will remove them and check behind them to see if there is dirt between them and the oil/thing.
I did notice that a fair amount of fins are bent up. I will carefully fix them and see maybe that helps.

Also I checked the fans with a volt meter, Either they are both going bad or they are fine, they are drawing the same amps and with a volt meter I cant tell anything is wrong.

Again, I bet that this is how it always is because the car is acting fine, and the needle is in the same spot as always, however now that I know the car is getting really hot, I may add a third radiator fan.

I am curious if driving around without the bumper off would make a difference,

I worry that if I take it to the dealer and they mess with it, It will be documented that the car was running hot and if the motor ever blows because of the IMS, the warrenty direct people will use that to not pay for anything. That is how it is in medicine at least.

Sounds like I have something to do this weekend!!
Thanks for all the help

[tradergarry]

Has anyone replaced the low speed fan resistors with radioshack ones? If so I would love to have the specs or part #. Resistors are $80 from Porsche and I need both a piece and I need both. Just replaced water pump, flushed coolant system, replaced radiator cap, hoses, cleaned radiators,etc.
and that's just the cooling system.

[pothole]

The fans on my '97 2.5 turn on at precisely 108 degrees C which is 226 degrees F. Pretty hot, but I believe this is correct, at least for my particular model.

I spent 10 days in Italy last summer. Every day was over 40 degrees C (= 104 F) and the car never went above 109 C (ie just one degree higher than the fan cut-in temp). Think I'd probably rather see the fan cut in around 105 C.

These temps are all via the digi display, not the temp gauge.