oldman40

After driving for about 30 min highway, I idled for about 15 min. I turned the auto start stop on thinking that I'd turn the engine off. It stayed on. During this time, the engine temp slowly creeped up to over 250 coolant and 240 oil and the engine overheat warning came on.

I cooled the engine down and drive home without issues. The next few days I continued to drive normally without problem. So I decided to try the auto start stop switch again and see if it repeated. Well, it did, so I think there is a reasonable association here.

Wondering if the auto stop switch is failing to restart the water pump or other cooling system component? Fyi-Coolant and oil levels are ok.

drmatara

take it to your dealer for inspection and let us know what was the issue...sounds pretty bizarre

Homeles

Stop using auto-stop?

chuck911

Back in the day these things were all directly driven so everything circulated, at least until something failed. This new engine though is so obsessed with squeezing every last erg of efficiency, it really is hard to know. There are several (I think I read 7?) Is that right?) independent electric pumps just for oil, plus who knows what for coolant. Even if the coolant pump is driven off the serpentine belt, who knows if the pump isn't clutched so as not to be driven unless needed, to improve warm-up time for example.

This is the kind of thing PCA Technical guru Alan Caldwell used to do so well. He'd write an article detailing all these systems, and we'd KNOW. Your hunch sounds right to me. Hopefully you'll be able to chat with the tech and find out more.

I'm curious, when you tried auto ss again, was it as before while you were already stopped? Or were you driving?

991TurboS

I still cannot get used to auto stop. It just creeps me out to have the car cut off like it does. I use it once in a while, but the engine going off and on is just too unnerving for me.

Jim M.

I use auto stop all the time and have never had an overheat issue, even in our Texas summers.

I'm not sure there are any electric pumps for oil when auto stopped. My oil pressure goes to zero PSI during auto stop.

oldman40

i tried it while driving. it worked fine during the drive time, only when I stopped again and idled (auto ss did not shut off the engine) that the overheat recurred. the over heat didn't respond to turning off the auto ss. to me it suggests a coolant pump failure since that heated up abnormally first and the oil second.

again my suspicion is a coolant pump failure, not oil.

agree and scheduled. will repost with their "diagnosis" and see what everyone thinks.

chuck911

My understanding is ss should stop when you do and start when you go. So if its idling its not working right. Right?

rnl

No. Battery voltage and engine temperature are among various factors which may dictate if the car turns on or off without regard to the status of the auto ss button

neanicu

" Thermal management

In the new 911 Carrera a thermal management system was introduced as a sports car specific requirement with the aim of reducing fuel consumption by directly controlling heat currents.
It was ensured above all in the design that a reduction in fuel consumption at partial load range was achieved without disadvantage to full throttle operation. The system must also permit rapid controllability and be lightweight.
The required changes to the engine consist of a single-slider map-controlled thermostat and a shut-off valve in the bypass circuit. The separation of the functions of coolant temperature regulation and bypass circuit shut-off offers advantages in temperature regulation and permits a heating boost in the warm-up phase with a weight-optimized design.
The system in the basic engine consists of only 3 additional components(shut-off valve and bypass line with tube).
With thermal management,the coolant throughput through the engine is completely suppressed by closing the shut-off valves in the early phase of the warm-up. This leads to faster warm-up of the cylinder head and liner. In the second phase,the shut-off valve is opened and the engine oil and transmission oil are warmed directly,reducing friction. "

atzonline.com


Just a little info about thermal management in the 9A1 engines found in the 991.
It seems to me that the water pump is driven off the belt,which means it's still a mechanical pump(Engine spinning means pump circulating coolant).
Your issue sounds very weird and interesting to me in the same time. Really curious to hear the diagnosis!
My bet goes to malfunctioning shut-off valve,which supposedly stops coolant flow in the warm up stage. It probably does the same thing when pressing the SS button.

MJBird993

I'm wondering if the reason the S/S was not stopping the engine is because the management system recognized that the engine was going to overheat, and so it kept it running to keep the water circulating. So the S/S may not be a cause, but rather a symptom.

Either way, something is amiss. Hopefully the tech will find it out rather quickly.

StudGarden

Seems like SS was somehow inhibiting cooling based on what he said. I always disable it except long road trips to get the sailing function. Even then it's muscle memory that it gets turned back off approaching an off ramp.

The gas it saves is so minuscule anyway and in most cases it puts the engine through another start cycle when even Al Gore would say it wasn't worth it. In those occasions you know you'll be sitting for a while in between moving, you can always re-enable it then.

One or two red lights on the left to have fun. One red light on the right always.

oldman40

Happened again today with coolant beginning to overheat but this time with auto ss completely off and the sequence started after pushing the e park brake at idle. Over heat process began almost instantly after I pushed the button despite having just been driving highway and city for 50 min with no issues. Dealer visit scheduled after xmas, will let you know what is found.

drmatara

What year is your car, MT or Automatic?

Z356

Look at his signature on his posts! Manual on a MY2013 Carrera S Cabriolet!

Louis: Good luck & keep us posted!

Saludos,
Eduardo
Carmel

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