Volkert

Sounds like a beaten-to-death subject however I have been having difficulty finding a cohesive overview. I would like to understand how the temperature management works on my 996.1 and what is considered normal behaviour when the cooling system is working optimally, as it was designed. Next question is what kind of modifications are available and what effect those have.

This is what I have derived, which might or might not be correct:

- standard thermostat starts to open at 187F (86C) and is fully open at 210F (99C) (= info from site Pelican parts)
- a LN low temp thermostat starts to open at 160F (71C) and is fully open at 180F (82C)
- car has a right and left radiator on which is bolted as well the AC condensor (l/r)
- right fan comes in at 201F (94C), high setting
- left fan comes in at 225F (107C), high setting
- with aircon on l/r fan also come at a low setting
- read out of temperature on dashboard (analog) is the engine temperature, probably close to thermostat and it reads the actual temperature. Thermostat is situated at entry of engine block cooling circuit so actually represents the lowest temperature found in the cooling circuit
- you can also read out the temperature digitally on the display of the airco unit
What I observed is that even at moderate outside temperatures (70F) after normal cruising at highway when entering the city with stop & go traffic the displayed temperature slowly goes up from 195 +/-5 to 225 when the left high fan also kicks in and then it slowly pushes down the temperature. To me, that does not seem very normal so I am considering either to swap to new the waterpump and thermostat (which I suspect are stock, this is a Jan 1998 car), I could then consider to insert a low temp thermostat (given feedback from ao mr. Raby indicates this makes a lot of sense). There is also a local shop here that claims to do an upgrade to the car that makes temperature management rock solid by installing a high volume waterpump (does that exist?), move thermostat to engine block exit iso entry and reprogram the fans so they kick in earlier.

To complete the picture I also understood that on Mk2 cars things work approximately the same but Porsche "fixed" the temperature gauge so it does not read higher then 190F (0 on the 180) even if the actual temperature is higher. Only when it goes to red zone, it flips to the right.

OK gentlemen, to the startline and go! Looking forward to your observations.

RngTrtl

just my 2 cents, but I live in the southern US and I have to really lay on the car and then sit in traffic to get above 215-220. Thats when its 90-95 degrees outside and humid as hell.

808Bill

I thought I once read that the 997 WP fits and is more efficient (I may be wrong) combined with the LTT you should be fine. Also reprogramming the fans would help too.
Start with the easy stuff and see if it helps...
Are you all tuned up with fresh plug/coil packs etc?

JimmyB

Also third radiator - some cars (tiptronics?) have it, some don't (probably yours). Been done to death on here.

FWIW I had a third rad and low temp thermostat (and new water pump) done at the end of last year, very happy with the result.

Volkert

Thx. How would plugs/coil packs impact temperature management? Or more general question? After addressing heat mgt my next target would be chain tensioners (car has run 85k miles sofar).

Volkert

Schnell Gelb

Just cleaning the radiators/condensers (Search) and relocating the temp sensor for the Purge Fan helps. Cost is zero.

Volkert

Radiators/condensors have been cleaned. Will check on purge fan.

Any feedback on the mentioned temperatures? Are these correct?

Volkert

Flat6 Innovations

The biggest benefit an early car cam see is a 3rd radiator, and use the updated CSF unit.

When I test early cars I am seldom happy with the coolant temps that we see today. The radiators are getting older and seeing some corrosion internally, reducing the thermal exchange capability of the unit.

The biggest issue I see comes from aftermarket bumpers with the wrong type of air inlets, and the proper shrouding to direct all the airflow through all of the radiator.. They stack all the air in at the outboard corners of the radiator, and only the back 1/3 of the radiator sees the proper air flow.

I have been developing an arrangement to help with this, and it has proven to help.

808Bill

I look forward to this new arrangement!

Flat6 Innovations

In the past few years I noticed that lots of cars that came here with intermixed oil and coolant, from cracked heads, and had aftermarket bumpers fitted. Some of the worst had the huge turbo inlets, which people often perceive with "bigger being better".

When I put the cars back together, they also tend to run hotter than normal again, and we have to work to address the cooling arrangement issues t remedy this- else our engine will fail, too.

I know exactly how hot these cars should run, and how the gauge should behave when driving my 52 mile test loop at different ambient temps.

Mike Murphy

OP, pretty much your post is accurrate. My car gets to 104C before the high speed fans turn on and up to 107C before it starts to cool down again to 104C. Only high speed driving gets the temps below that for me when ambient temps outside are high (70-85F). In the winter or below 50F outside, high speed driving has my temps sitting between 89-93C.

Based on all this, including Hartech research, it makes sense to get these temps down rom where they are today. Cleaning the rads, moving the sensors, and doing a low temp t-stat are probably the best bang/buck. A 3rd radiator would be better.

Normally, 107C by itself isn't going to cause a problem if the car is just sitting in traffic, although I still think 107C is too hot. But at that temp, if someone were to open the throttle and put the hammer down, we now have a sudden and rapid increase in localized heat that has to exit the engine and make its way back to the front of the car to be cooled before it goes back to the engine to cool the engine. And Coolant coming into the engine might not be that cool because air wasn't moving past the radiators to cool it down fast enough. Therefore, internal temps could very well be higher than 104-107C, and if oil temps are generally 10-20F higher than Coolant, we could start to see very low viscosities near the hottest parts of the engine, which can lead to a breakdown of the film layer, resulting in metal to metal contact.

Moral of the story - low temp t-stat and whatever else you want to do to get the temps down should increase the life of the engine in hot weather.

And don't worry about winter driving not being hot enough to vapor off any accumulated water as long as you change you Oil every year and don't take many short trips.

Volkert

No aftermarket no-nothing on this baby. I like to keep her stock but with refinements internally.
I have read in some threads as well that after waterpump/LTT replacement still temps were too high and only solution was to replace the radiators themselves as well.

What are some thoughts on moving the thermostat to the outlet (so it acts quicker on added load to the engine)?

Silk

Some thoughts on mods for the cooling system.
Actually my Indy has done them.

- relocate the (low temp) thermostat at the exit of the engine: quicker response to high temperature conditions.
- water pump with more capacity and modified with slightly smaller pulley: especially at idle and slow speed significantly more water is moved compared to stock
- reprogram the ECU to switch on the radiator fans at a lower threshold temperature. Relocate temperature
Sensor to a hotter zone.

Flat6 Innovations

But.... What happens when the response time is too fast? The cooling systems of these cars don;t need that much "help".

But at high speed the pump cavitates. Been there, done that.

These two things can be done, again, the CLT being moved has caveats with warm up times, sensitivity, and etc. The stock sensor is in a poor location, but a strategic location.

dan_189

Any downsides to running a 3rd radiator?

Don't have any problems with the cooling system but we do get hot summers here although winter is cool but not freezing. I'd like to have the 3rd rad for piece of mind and it looks awesome and better than the plastic block off section (might be more of a 6speed mod comment haha)

Now that its getting colder my Mk2 C2 temp gauge is at the start of the 0 at op. temp (my gauge goes 0 - 80 - 120).