ejdoherty911

Stock thermostat. I don't mess with the coolant, bad idea. I purchase OEM coolant, I wouldn't even consider anything else and follow the directions exactly as far as 50/50.

tharbin

ohlins, don't think about the coolant like it is antifreeze. Always run the recommended mix as it is actually like buying concentrated (enter your product here). The water is to turn the concentrate back into full strength coolant.

docmirror

Um - don't want to be a noodge, but 'coolant' is synonymous with antifreeze. The job of the coolant is to transfer engine heat to the radiator for dissipation. Since ethylene or polypropylene glycol is a lower thermal coef than water, using less in the mix will improve the cooling capacity of the 'coolant'.

For the OP, I would suggest the low temp T-stat. I put one in a few weeks ago, and it's a great investment. I do not track, but I was sitting in city traffic today with the AC on full and the temp around 90F and the gauge never got over the tick at 180. It used to sit between 190 and 200 on the gauge.

tharbin

Anti-freeze is not synonymous with coolant. It is true that anti-freeze can be used as a coolant and it is true that anti-freeze is a component of most coolant mixes but not all coolants (e.g. water) contain anti-freeze therefore they are not synonymous.

The point was that there is more to a coolant concentrate than just its anti-freezing properties and that each coolant concentrate is engineered to work best at specific concentrations.

Yes, I'm well aware that water has better thermal conductivity than anti-freeze mixes. When I was growing up it was common to add anti-freeze in the winter then flush the system and replace with water in the spring. There is more to modern coolants than merely conducting heat away from the heat source, they also contain corrosion inhibitors, possibly a component to lower the point of solidification appropriately, possibly some lubricants even coloring agents.

Thank you for your information to the OP about the low temperature thermostat. I have been looking for post that contain real-world results from their use. After a one or two hour ride at 75-80ish mph and then pulling into stop and go traffic when it is 110+ out frequently makes me a little nervous because, while the cooling system eventually catches up the system seems overwhelmed for the first few minutes after entering traffic.

speed rII

This or some electric problem that makes the ignition timing late.
Doubt that it's the timing thou...
Dirt inside the radiators will reduce heat dissipation, even if the flow is still close to normal.

Mayby test with some coolant cleaner and a good flush first? If there is dirt/smudge in system, you should try to clean the whole system, not just the radiators.

996R

Here I do experience exactly the same issue as ohlins8990 describes. I live in Southern Alberta, so heat would not be the biggest issue. Also changed water pump, thermostat to 71C, new expansion tank cap.
still comes to a boil when idling too long. The last thing I can come up with is clogged radiator. Since its going from left to right(as I read somewhere), I'm about to change the left radiator(or both) as soon as I learned of more issues with the 996 radiators.

Youri Ko

Stupid question, but can anyone provide some info about the "A/C hack" - I did google it

Thanks

JimmyB

https://rennlist.com/forums/996-foru...agnostics.html

Youri Ko

Thank you Jimmy

Slakker

Just double checked. Needle in the middle of the 0 on 180 is 217degrees according to the AC.

speed rII

From the link that Jimmy B posted:

"Forget about the climate control "diagnostics" - they are pretty much worthless.
I have both a PST2 and PIWIS tester and those climate control "diagnostics" never match up with the Porsche tool readings.
Buy the Durametric software/cable and get the same information Porsche gets with their expensive diagnostic tools." -Loren

I would do as Loren suggests

Slakker

Except that the Durametric doesn't show engine temp for the '98/'99 model years.

CarlOrton

So, why is it that the a/c panel shows one temp, and the tools show another? Different sensor locations? Just trying to learn....

Macster

That's normal behavior. At highway speed air is being forced through the radiators and the coolant kept cool(er).

If you slow from highway speed to surface street speed without the air flow through the radiators the coolant temperature will rise and can rise until the radiator fans are switched on to at least low speed (by my observation at 212F).

High speed is switched on if the temperature climbs to 216F.

It can take some time before the temperature comes down. There is a lot of hot coolant and it is hot because the engine is hot and there is over 400lbs of hot engine.

Might add that every new MY one of the points Porsche makes is "better aerodynamics" and "better cooling".

Unfortunately with a '99 MY you are starting with a car that has the original cooling system which mainly differs in how efficiently air is routed through the radiator ducts and this is somewhat determined/affected by the aerodynamics of the car.

This aerodynamics is important.

I can tell you my 2003 Turbo can cruise down the highway -- and has -- in 118F ambient temperature at highway speeds (75mph -- this in AZ) and the coolant temperature gage needle doesn't get above the "180" hash mark. The A/C was on so the fans were on but the cabin was at a cool/comfortable 72F and the cabin fan was not runing very fast at all. The temperature is of course hotter than that being around the 200F. (The temp gage is a very crude/imprecise "instrument" and is really only good for knowing the engine is cold, warm, hot (up to temperature hot), and too hot.)

In even less heat -- 116F -- my 2002 Boxster's coolant temperature was "pegged" at 226F and both fans were running at high speed. I had to shut off the A/C because it was blowing hot air. Might note while the coolant temperature was at 226F it didn't get any higher. No warning lights came on and the engine was unaffected as that was years and hundreds of thousands of miles ago.

The above highlights the difference in aerodynamics and of course cooling capacity. The Turbo has 3 radiators, the Boxster just 2.

Be sure the radiator duct rubber sheeting is properly positioned. I've seen this sheeting move out of position but why I do not know. The passenger side of my Boxster has the sheeting hanging down into the opening in the bumper and I know this can and does affect the amount of air flow through that radiator duct.

I have in the past managed to when the car is hot from being run and then sitting in the sun force the sheeting back into place without having to take off the bumper cover. It takes some effort as it is pretty heavy/thick rubber.

With the fans running on low speed do you feel about the same amount of air being blown out from the fans' exhaust side? With the engine up to temperature is the air about the same temperature? You can get two relative inexpensive digital thermometers and tape them so each's temp probe is in the air flow and then check the temperature reading.

Just because a fan is running doesn't necessarily mean it is spinning as fast as it should be. I had one Turbo fan that was running yet the air flow from behind the fan was pathetic. The tech checked and found no fan motor stage errors but did note the fan motor was drawing lots more current than the fan motor on the other side and I had him replace the fan motor.

In another case -- earlier -- I found one fan not blowing any air at all. What had happened was the fan motor shaft had snapped. Tech said he had never seen a fan motor fail like this.

For tracking often times the track prohibits the use of anti-freeze. So many use a water wetter. This will not protect the engine from freezing. Whether it contains any anti-corrosion additives or additives to help lube the water pump seals I don't know.

I do not know if this water wetter is "better" at cooling then a proper blend of anti-freeze and water.

My advice would be to install a 3rd radiator.

I'm relucant to advise you to make aerodynamic changes but one change that has been proven to be helpful in the past with other cars is to install an air dam. This of course hangs down and forces air to flow around/over the car rather than under the car. This lowers the air pressure under the car and this lower pressure helps pull air through the radiator ducts.

But you want to be careful the air dam doesn't deflect and create lift.

Woodman71

TIL there's such a thing as "water wetter."