dannyk304

Hi all, yesterday my 2016 C2 began to overheat when stuck in a bit of traffic after about 30 minutes of a spirited drive. About a week ago, I got the coolant fault and code was for Vacuum system leak, and after looking over the engine for any loose vacuum hoses (all looked fine) and there was no overheating issue that I noticed, I reset the code with my Autel and it hadn't come back. But yesterday, after about 30 minutes of good driving, and as I was stuck in slight traffic I saw in my side mirror billowing white smoke, oil temp was at 225, coolant at 194. While the oil temp was higher than I normally see it, there was no code or fault at all, the car acted as if it was normal. Pulled over, fluid was dripping from the driver's side - pretty sure the expansion tank excess fluid drain. The radiator fans (front of car) were not running at all, nor were the engine bay fans. When I turn the AC on the fans are running on low speed. The heater works and was actually blowing very hot air. I waited for the car to cool completely and traffic to die down and drove the car home 20 minutes away with AC on and heater blowing on high, oil temp stayed below 200 the whole time. I have checked the forums, I'm leaning to one or more COVs (all of mine are the updated - newest versions) and particularly the Coolant Shutoff Valve on Engine Bypass Circuit. Other thoughts appear to be radiator fan relays but I don't know why the 2 low speed would be fine but the 2 high speed wouldn't on both simultaneously. Other issue I read could be the expansion tank sensor? And last idea I have could be the thermostat. Any thoughts or input will be greatly appreciated. I'm going to switch the coolant bypass COV with the symposer today to see if that does anything but any other ideas for me to check or do while I've taken apart the rear of the car will be helpful. Trying to find out what the coolant shutoff COV is responsible for - anyone know? What else would tell the DME the engine is hot and needs to turn on the high-speed radiator fans? Thank you all for any advice, happy new year.

dannyk304

Update on above, if anyone with some idea can chime in I'd be grateful as I'm a bit stumped. Took apart the entire rear, checked all the possible to reach vacuum hoses and all seemed fine. switched the engine coolant valve bypass COV with the PSE which hasn't been working from the start, cleaned the engine bay, slapped it all back together and ran the car idling to warm up. She came up to temp normally but the radiator fans never turned on with AC off and she started dripping from the expansion tank overfill thereafter. With the AC turned on the fans do blow on low speed. The gauges read normal - the fabulously wrong 194F for coolant and oil hit the high of 210F. However, my Autel scanner measured the coolant at 104 Celcius, so over boiling at 219F. What could cause this? It seems something is not warning the computer and turning on the radiator fans. If it were one fan I'd presume the fan was blocked or broken but for both to go together seems more like a controller issue. Also, while the coolant gauge is a dummy shouldn't it sense a problem at 219F and throw a warning? Shouldn't I get some sort of code/warning of any kind - at what temp does the stupid 194 finally change to reflect an issue? I am stumped and could use some insight, what signals the radiator fans to turn on? Could it be the sensor in the expansion tank? Is it likely that the high speed relays for each fan failed simultaneously? Where are these relays? What might I be missing? Given the original code was P1433 Vacuum System Leak - Coolant System Fault might it be the vacuum pump - would that cause this? The system seems to be holding vacuum as it hissed when I disconnected the vacuum lines from the COV.

barncobob

time for dealer Id say,,just went thru this disaster with my 17 with the known water pump issues.

Autobahnschreck

Real 104° C (or about 219 F) is just a normal cooling fluid temperature for a 991 motor operating in "Normal" mode" . It will be reduced to around 185 F in "Sport" or "Sport+".
The fans will not start running below ca. 107° C (or about 226 F), if not required bei AC.
The dashboard instrument/display indication will remain at 194 F until the true fluid temperature is about 230 F or more.
Onset of boiling will be beyond 125° C (260 F), unless the cooling system looses its pressure due to massive leaks.
You report you saw water dripping out and white smoke, while the temperature indication remained at "194 F". To me this means, your cooling fluid boiled, but at a temperature it does only at athmospheric pressure. My Conclusion: Your cooling system does not keep pressure as it should.
The first suspect for me would be the cap of the expansion tank with its integrated valve.

dannyk304

Thank you! I think may be a great direction to look and I appreciate your insight. I drove the car today while monitoring live data from the Autel and it never went above 95C in sport, mostly stayed below 90 between about 84 and 86, and engine oil remained well below 90 most of the time. Yet...when I stopped the expansion tank excess drain started dripping again. I think you're right about the loss of pressure being the issue. I will change the cap, it looks perfectly fine but and easy place to start. Now, do you think/know if this would cause a Coolant system fault - P1433, Vacuum System Leak code? Again, thank you!

Serge997

Funny I came across this. Got the exact code/warning on my 2014 C4S a few weeks ago. No dripping and temps the “194” for water and 210/230 for oil in traffic. Checked everything and if anything found my coolant level maybe a third of a gallon low.

Spoke to indy, cleared the code and went my merry way. About a week later I get the same code/warning. Again no signs of overhearing. Checked with my scanner and temp was 91c.

That time I didn’t clear the code and made an appointment at dealer (next week). I was 159 miles from home when it happened so decided to drive back using the scanner as a triple check temps were ok. They were.

I’ve had to move the car a couple times after that (2 minutes) and the warning was always there …. but over the weekend had to use the car for an urgent matter and suddenly the warning was gone?!?! It was there when i started driving and suddenly it went away ….

So, can it be that there was a BOV acting up in a place of the system not related to engine cooling that decided to stop acting up?

I don’t want to show up at the dealer and get the “you owe us $150 for nothing because the car has no warning up”, or the “we see the code so we need to spend 8 hours checking all the COVs and even if none is damaged you owe us $1,200 for the eight hours”.

Thoughts? I’ve had warning message in this and other cars before. I’ve never seen one go away on its own.

Joec500

I had something like this happen and I found it was a loose hose to my PSE actuator. I then zip tied the hoses and it’s been a month and never came back. My guess is there is a lose hose somewhere. I would get a smoke machine hooked up to your vacuum system and find the intermittent leak.

dannyk304

Thank you again, @Autobahnschreck, for all of this good information, and the cap was certainly worth a shot but it didn't change anything unfortunately. I am convinced there is a pressure leak in the system given the above information, and looking over the coolant system diagram I am a bit daunted with all the components. However, there appears to be absolutely no fluid leaking anywhere on the car, except from the overfill hose on the expansion tank. I am going to change the expansion tank at this point, just placed the order, perhaps it has a hairline crack I can't see. Is there any other component that you think could fail, causing pressure to drop but not actually leak fluid? If there were any major leaks wouldn't fluid drain from those? Unless it is a COV or some component operating on vacuum that fails and releases pressure - what could that be?

About 20 minutes into my drives, just after the coolant hitting 194F on the gauge but when the oil registered around 200F the "Fault - Coolant System" code popped once again and then when I parked I saw the drip - drops really - of coolant coming from what appears to be the overfill hose over the driver's side exhaust. Every time I clear the code, it resurfaces when I'm back up to operating temp. The car drives perfectly, the temps stay in good range, there are no other codes. The day I had a lot of smoke and a lot of fluid loss I was in "Normal" mode so the coolant temp was at 219 therefore exacerbating the boil. I drive only in Sport now to keep the temps lower, thanks to your info on operating temps. Would a small crack in the expansion tank cause this code - when coolant hits a certain temp the pressure pops something which ultimately releases pressure and generating the code? Not sure why "Vacuum System Leak" is associated with coolant except for the few COVs related to directing the fluid to certain components, but none of these seem to be leaking fluid. Is there a way to test each COV for failure? Everything I've read said a loose vacuum hose or a bad COV can cause the Coolant System Fault...BUT...I feel those would be unlikely to cause a system pressure loss without fluid leaks and be associated with premature coolant boil thus expansion tank overspill. I'm associating the fault code popping up as soon as the fluid hits operating temp and expands, so I think there is a physical leak of pressure somewhere. Thanks again for any insights.

wkearney99

Where does the overfill hose come out? Anyone got a picture of where to look? I had my water pump, thermostat and valve block replaced and seemed to continue to have some issues with a slight coolant smell.

That and have there been any issues with age of vacuum hoses and premature failures? The rubber in most hoses doesn't last forever but failure on a 991 would seem too soon.

dannyk304

It's hard to see - runs down the back of the expansion tank and stops up above the driver's side exhaust near the rear. If you open the cap, you'll see a small hole in the outer ring of the fill neck, which connects to a short hose on the outside and it drips right onto the exhaust pipe leading to the center muffler. It is clearly not from the pump/thermostat location.

barncobob

first time mine overheated it puked coolant left rear...dealer check exp tank etc, put in new thermostat 2X, good for a week, Im on my 3rd water pump in 50K..they replaced pump, valve block, vacuum pump, hoses etc..My new LC 500 is showing up at end of Jan. and Im selling the Porsche...2017 S.

wkearney99

yeah, you did have a run of bad luck with getting that thing serviced.

wkearney99

I have a Targa so it's kinda difficult to get a close look at the filler assembly. I was thinking more about the bottom end of the hose, and where it comes out.

dannyk304

So after letting the car sit a few days, I went to check and it is dripping coolant from the driver's side even when sitting and cold. Without the crazy removal of parts, I took out the engine bay fan and stuck my hand around a bit and sure enough the coolant tank seems to be leaking from the seam along the bottom of the tank. I'm concluding the tank has a fracture/crack. I also learned that the entire country has no Expansion Tanks in stock, they're in Germany and they won't be available until end of Feb/early March. Ouch - I just bought a used one off Ebay that belonged to a car with 13k miles, I'm hoping it'll hold until FCP gets the part. That said, I'm still trying to understand the coolant system a bit - particularly why tank rupture would pop a fault code indicating Vacuum Leak? where's the vacuum connected to this? Most of the coolant flow is pretty simple to grasp but I'm unable to find any information on the bleeder valve operation and the 2 hoses that come off of that - one is called Coolant Vent Line but again, I don't see any information on this. @Autobahnschreck or anyone who may know how this line works, to what it connects on the other end? And might this have any bearing on the Vacuum leak code? Or does the DME just state Vacuum leak by default when there's a loss of pressure in the coolant system in general? Thanks again and I'll follow-up once I've installed the new (used) Expansion Tank.

barncobob

dont U just love all the aggravation.