art911

Hello,

I am experiencing higher than normal coolant temperatures. Car is 2001 3,4 C2 and the temperature reaches 100C instead of 84-85 that it was usually working.

Does this car have 2 fan stages ? How can I tell If both are working ?

What else should I look at ?

Thanks
Art

David A

You might have a bad water pomp,it would be a good idea to change your coolant and ad a 3rd center radiator if your car is manual.

1999Porsche911

Your engine temperature was NEVER running at 84 - 85C once it was fuly warmed up. Thermostat is set for 83C. Around town, it is common to see 100C and you will see 105F + at times also. If you want to reduce the temperatures, you will need to increase the airflow past the radiators. High temperatures in these engines is caused by too low of coolant flow combined with insufficient airflow at lower speeds.

Here is my fan mod that many have done to eliminate the problem:

Radiator Fan and Engine Compartment Fan Switch Mod


The 3.4 996 runs extremely hot when driving around town in temperatures higher than 75 degrees. This mod is a way to reduce coolant temps back to a safer level, helping to reduce oil temps and improving performance.

The mod consists of installing a switch that will allow you to turn on the high speed radiator fans at any time, while maintaining the automatic operation of the fans. We do the same for the engine compartment fan.

Radiator Fans

Connect a wire to the ground of the 2 high speed fan relays located on the relay carrier located in the driver’s side foot well. The relays are #20 and #22. Feed this wire to where your switch will be located. Connect the wire to one side of the switch. Connect another wire from the other contact on the switch and then connect the other end of this wire to a chassis ground point.

With key on, this switch will now immediately turn on both radiator fans providing maximum cooling. When you turn the key off, the fans will continue to run for about 5 seconds until the relay shuts down. Your fan operation remains normal when the switch is off.

BruceP

Are you reading your temp from the gage or from the OBD? Also, anything different about the driving conditions? To me, the operating temperature you describe isn't unusual; I'd be more concerned about a change that you can't explain.

My car will routinely exceed 100 degrees celcius in slow traffic on a hot day. I've never heard the fans come on, but have had them checked and I know they're working. Yes, I believe they are two speed fans, to answer one of your questions.

art911

First of all, thanks to all the suggestions. I have had this car for two years, and never experienced this before. The problem is that the higher than normal temperature is combined with a very low oil pressure. I get 0,5 on idle and doesn't exceed 3bar at 5k rpm. What about that then ???

I don't get a low oil pressure light though

Art

1999Porsche911

Regardless of what oil you use you will never have coolant temperatures of 84-85C. However, a hotter running engine will also cause your idle pressure to get as low as .5 bar if you are running Mobil Water in the crankcase. IMO, I would first get rid of the 0W40 and move to a weight oil that will better protect your engine. IF your pressure reading is in fact accurate at 0.5 bar, you have greatly increased your risk of bearing damage as that is not nearly enough pressure to maintain proper clearances. Throw in a 5W50 or 15W50.

pszikla

The lower oil pressure can simply be that since oil becomes thinner as the temperature gets higher, it is your higher temp. that is lowering your oil pessure.
When you start your engine and while warming up, your pressure will likely be much higher.

BruceP

Um, no. You see those two numbers? 0 and 40? The first one is the cold viscosity, and the second one is the hot viscosity. Under any halfway normal circumstances, a warm engine won't thin the oil for heaven's sake.

I think you should see a mechanic about your oil pressure issue (which may well be related to the cooling, since oil plays a role there, too). My car, which 1999 would tell you operates at dangerously thermonuclear temperatures, operates at much higher oil pressures than that at 5,000rpm. You have a problem, it probably won't get better by itself, and if it gets worse it could cost you an engine. Far from engine heat causing the oil pressure problem, I think the opposite might be the case.

1999Porsche911

You clearly do not understand oil. Take a look at the HTHS Viscosity and cSt specs of a Mobil Water versus even their 10W40. The 10W40 is clearly the better choice. A 0W40 oil does not have the same high temperature protection as does the 10W40, regardless of what the marketing states. The weight indication only tells you what the non pressurized flow rate is of the oil is, from which, NOTHING can be concluded as to it's benefits to an engine.

pszikla

Bruce, although you are partially correct in your statement on multigrade oil, it defientley does change viscosity with temperature regardless.
I do agree that ART911 should probably have the car checked out for his own peace of mind but perhaps this article will fill in some blanks on oil viscosity including multigrades versus temperature.
Notice the last graph that shows viscosity versus temp for a multigrade oil.
Cheers
http://www.wearcheck.com/literature/techdoc/WZA007.htm

BruceP

I was simply employing some rhetorical economy. I understand oil very well, and the idea that the oil being hot would lead to low oil pressures under anything close to normal circumstances is absurd. The gentleman that started this thread has an oiling problem, which is contributing to higher operating temperatures.

BruceP

I don't know which of Mobil's competitors you work for, but you are in no position to declare what I do and do not understand. When you start your own car company, let me know. In the meantime, you are a stranger on the internet with no discernible credentials. I stand by my advice to the original poster that he should have someone look at it who knows what they're doing. There is at least the strong possibility of an oiling problem which is causing his operating temps to rise, and that means his engine is at risk.

michael.s.under

Very common for P cars to seem running high temps, do a fan mod ^, clean your radiators, add a radiator. I did a coolant flush and added water wetter. Seemed to help. My car hates the AZ heat.

1999Porsche911

So, let's make this clear...you are stating that a 0W40 oil will NOT have a lower oiil pressure than a 10W40 oil at the same engine speed and oil temperature? If that is the case, then you are dead wrong. The fact is, 0W40 will ALWAYS have a lower oil pressure. If you don't know this to be fact, then lay off the advice.

BTW: I never stated that I do not run Mobil oil.

BruceP

Don't put words in my mouth. Here are facts:

1. I have the same engine as the poster.
2. I run Mobil 0W40, as recommended by Porsche.
3. My oil pressure is higher than half a bar at idle, even with the engine at 100 degrees C.
4. My oil pressure is much higher than 3 bars at 5,000 rpm, again, regardless of temperature.
5. The poster was not asking about a normal operating condition. He was asking about a change he noticed, a change that did not seem to coincide with switching oils.

It is therefore simple, pure logic that something is wrong, and that something is not his long standing choice of oil or lack of a third radiator or fan mod. If nothing changed in his circumstances, then something has gone wrong in the motor. This is immutable.

Stop preaching your same old story and help the guy out. If you can't help, then holster it until the next time someone asks about oil viscosities.