Dirty Radiators or bad waterpump?

[GForce83]

Hey guys -

quick question for you. I have a '00 996 cab with 44k miles. When I drive on the highway, engine temperature runs completely normal at 180. But when I slow down in traffic, is slowly eases up to 190 and then when I drive again, it slowly goes down to 180.

It doesn't sound like a waterpump issue. Does it sound like i need to clean my radiators?... i hope it's nothing too major. I just noticed this a few months ago. I changed the coolant and it hasn't helped. I live in TX and the temp is already upto 90 degrees. Let me know what you guys think... Thanks!

[Loren]

If your water pumper had failed then it would always be hot. 190 is not that high you have a minor problem.

I suggest the following:

1. Are you sure both fans run - one in each front fender well. They have two speeds slow (when the coolant is hot) and fast when the AC is on (or the car is very hot).

2. If you have never cleaned the debris from the front bumper air intakes it is probably worthwhile to do that. Several folks have written up the process here.

[GranburyChuck]

Hey GForce,

I too live in Texas (Fort Worth). My car was experiencing increasing temperatures recently (just as the weather is getting warm). Usually it rides at the bottom edge of the 0 on 180. When I stop at a traffic light for a couple of minutes it would rise into the far side of the 0 on 180. This is after I had cleaned the radiators. I got a lot of junk out of them but most concerning was the tar that had built up inside the fins. I assume this came from road construction on highways were I live. Temperature was still increasing more than I had expected. So I looked at the radiator fans. One of them was not working. I swapped out ballasts for the fans and this indicated the ballasts were okay. I had to replace fuses several times. I came to the conclusion that my resistor (located under the nose of the car below the radiator) was out. I replaced this ($90 from Park Place Porsche). I could tell my old one was burnt out by doing electrical check. I started the car and noticed a burning smell. Shut the car off and looked under where the resistor was. It was smoking. I reached up to check the fan was free (car off) and burnt a hole in my hand on the resistor. When that cooled I reached under the car to spin the fan blades. Drivers side hard to turn, passenger side spins freely. So it was the fan all along. Ran out of time to do the work myself (this is my daily driver) so I took it to Autobahn Porsche. I think it was around $500 to replace.

So my take on it is this: when car is cool reach underneath and spin the fans on both sides just to make sure they spin freely, second clean the radiators (only takes about 2 hours unless you have to spend 3 hours cleaning out every little fin). That is the easy work. Also check the fuses and ballasts (this is if you find your fans are not working). As Loren points out when the temperature of the car is up at operating temps and the A/C is on then the fans should spin at high speed (can hear a definite loud whir sound and placing hands down by intake can feel sucking air).

[perryinva]

This may be a stupid question, but I just spent 4 hours removing my front bumper cover, and drivers side fender liner to replace the series resistor and clean out the radiators(all went well, bought resistor for $58.24 +S&H from Sunset), and I was wondering ..why does the bad resistor prevent the fan from operating at high speed..I thought it was only needed to drop the voltage for low speed fan run? It's moot because everything works great now but just curious.

[GForce83]

Hey GForce,

I too live in Texas (Fort Worth). My car was experiencing increasing temperatures recently (just as the weather is getting warm). Usually it rides at the bottom edge of the 0 on 180. When I stop at a traffic light for a couple of minutes it would rise into the far side of the 0 on 180. This is after I had cleaned the radiators. I got a lot of junk out of them but most concerning was the tar that had built up inside the fins. I assume this came from road construction on highways were I live. Temperature was still increasing more than I had expected. So I looked at the radiator fans. One of them was not working. I swapped out ballasts for the fans and this indicated the ballasts were okay. I had to replace fuses several times. I came to the conclusion that my resistor (located under the nose of the car below the radiator) was out. I replaced this ($90 from Park Place Porsche). I could tell my old one was burnt out by doing electrical check. I started the car and noticed a burning smell. Shut the car off and looked under where the resistor was. It was smoking. I reached up to check the fan was free (car off) and burnt a hole in my hand on the resistor. When that cooled I reached under the car to spin the fan blades. Drivers side hard to turn, passenger side spins freely. So it was the fan all along. Ran out of time to do the work myself (this is my daily driver) so I took it to Autobahn Porsche. I think it was around $500 to replace.

So my take on it is this: when car is cool reach underneath and spin the fans on both sides just to make sure they spin freely, second clean the radiators (only takes about 2 hours unless you have to spend 3 hours cleaning out every little fin). That is the easy work. Also check the fuses and ballasts (this is if you find your fans are not working). As Loren points out when the temperature of the car is up at operating temps and the A/C is on then the fans should spin at high speed (can hear a definite loud whir sound and placing hands down by intake can feel sucking air).

This is exactly what I'm looking for. Thanks so much for the info. I'll let you know what I find out.

[GForce83]

I originally removed the bumper and cleaned the radiators, but was still noticing the problem.

I found out it was some crap stuck between the radiator and the condenser nothing else. I took it to the dealer and they cleaned it out for me. Thanks to everyone for helping me out.

[KevinMac]

I originally removed the bumper and cleaned the radiators, but was still noticing the problem.

I found out it was some crap stuck between the radiator and the condenser nothing else. I took it to the dealer and they cleaned it out for me. Thanks to everyone for helping me out.

So does it run consistanly @180. Because everything I have read in PCA is the variation between 180 and 190 is not a problem.

From PCA

"I have a 2001 C4 Cab with 17000 mi. In ambient temperatures above 80 temp needle reads about 200-215 degrees, or about 1:00-1:30 on the gauge. Cooler ambient temps result in cooler running, although it is always above 180. Cooling fans are operative. Dealer says this is normal for the 996.

Is it??

Your dealer is correct, this is normal. I checked with Bruce Anderson on this one. Here is what he had to offer; "Water temperature is not as critical as oil temperature... as long as it isn't boiling it is still doing it's job. Higher ambient temperature equals higher engine temperature. Too hot will have an engine temperature light blinking. I have seen coolant belch out the breather overflow without turning the light on. The non tiptronic cars have two radiators and the Tiptronic cars have three. If it's a track car you might want to add the third cooler."

Edited June 6, 2008 by KevinMac

[White987S]

Ever since my car was new, and every time I wash it (2-4 times per month) I take the leaf blower, and blow out the front radiators. Lots of crap comes flying out each time. I do this dry, prior to washing, when everything is dry and again after the area has been wet, and a little more stuff works out.

This works for me.

Might not work for other owners who are starting out with a dirty or clogged radiator.

Just an FYI.