Hi All,

I have a 2015 Cayenne S with 78k miles on it. I was recently driving and suddenly the temperature started to spike and then drop while on the highway, so I figured it was probably just an electrical issue and kept going until I saw a warning that said engine hot, shut down. So I pulled over and turned the car off. I let it cool down and then got it home since I was fairly close. I noticed afterward that there was some coolant on the floor of my garage, so I refilled it and it continued to overheat when I would drive it (not long-distance, just in the neighborhood to check). I kept looking and saw that the vent tube had a huge crack in it on the driver's side, so I replaced it. After replacing the vent tube I refilled the coolant, and let it warm up to check if there were any leaks, nothing was found and it was not overheating at idle, so I decided to drive it around a little bit (neighborhood again). As soon as I started driving the temperature started climbing, so I turned it off and let it cool down. I assumed there was an air bubble in the system, so the next morning I put the car on an incline took the radiator cap off, and let it run so any of the bubbles could get out. After quite many bubbles got out I capped it, let it cool, refilled the reservoir, and drove it around the neighborhood for 10-15 minutes and all was fine. I decided to take it out for a longer drive and as soon as I went down the street (.25 mi) the temperature started climbing (only got to 206) and I saw a puff of white smoke so I turned it off and coasted it to the nearest parking lot. The puff of white smoke makes me think the head gasket might have blown out at some point. Scouring the forums, it seems like head gasket issues are quite rare on this vehicle and Porsche supposedly has systems in place to "kill" the car before any damage happens due to heat, but the puff of white smoke is worrisome. I checked the oil cap and didn't see any milky residue, so I am hopeful, but not sure what else it could be. I also do not smell any coolant in the exhaust fumes.

I will more than likely get it towed to a shop at this point, but wanted to see if anyone has any thoughts on what it might be.

 

Its possible you have some coolant in the engine bay which evaporated off causing the smoke, but from what you have described it sounds like you need to thoroughly bleed the coolant system which is not easy to do on these cars without a vacuum purge.

I just did a coolant flush on my car (after my driver side vent tube failed too) and it took me about a full day of bleeding using one of those "No leak" fill jugs and lots of squeezing the radiator pipes to finally be satisfied that i got all the bubbles out...

I have never heard of anyone blowing a head gasket on these cars so far, so hopefully it isn't that... I would double check to make sure your coolant is actually bubble free.

 

OP,

After you repaired the leak, the cooling system needs to be refilled via a vacuum refill tool and process. Search is your friend, e.g https://rennlist.com/forums/cayenne-...ant-flush.html as is AllDataDIY or Mitchell's

 

Thanks for the insights.

The smoke did smell like oil instead of coolant and the water temp was only at 204 when I saw the puff and decided to pull over instead of risking damage, so I am thinking some oil got in the intake. Doing some more digging online I found that in a lot of cases when the car is parked on an incline for a while which I was doing in an attempt to bleed the system oil pools in the turbo and there may be a puff after that. So I am hoping it was that, I have the car back home now after it cooled in the parking lot for a while. There were no issues while driving it back and I also drove around my neighbourhood for a while and no issues at all.

I am going to purchase one of the vacuum bleeders (unless someone is in Atlanta that has one and wouldn’t mind letting me borrow it) and seeing if I can properly bleed the system. Hopefully it’s just a couple more pesky bubbles in the system and all is good.

 

Thanks CAVU! I did see that thread, quick question, I see a note in there from you that the thermostat cannot be activated. Do you just mean that this should be done while the engine isn’t too warm or maybe even off? It seems like I just need to place the vaccum unit on the reservoir, let it build a vaccum and then close the valve on the vaccum and let it pull in fresh coolant to reach ambient pressure. Does that seem right?

 

The caution about the thermostat not being activated was straight from Porsche repair instruction via AllDataDIY. I would be guessing as to why. AllDataDIY does not yet have the 2015 Porsche in it but Mitchell's DIY does. There are several steps involved and in your case, a bleeder valve assembly set to service position, some coolant will have to be drained before initiating the vacuum fill process, etc.

 

Thanks! I had searched AllDataDIY but didn't see anything there. I will purchase Mitchell's DIY and go based on the instructions there.

 

Good Plan. I do not think we have a DIY for coolant refill, so take lots of pictures and notes and be the first!

Good luck with the servicing!

 

Yup will do for sure!

 

I am having the same issue with my 2014 base Cayenne! Any updates on yours? I pretty much went through the same steps that you did with no luck yet. Im hoping you can point me in the right direction before I have to drop it off at the dealer $$$...

 

My '15 turbo temp gauge has me biting my nails while driving. It goes up, then goes back down a little, then creeps back up then goes back to normal. Bi-polar!

The last time it went up up.... Display said pull the f over. I got it towed in and had the thermo and water pump replaced and they found a cracked coolant line. The one that has the problems for everyone. New coolant also and had new plugs installed. All factory oem parts. Now it's doing the same up and down effect, and to top it off I have 2 CEL for the EVAP system.

I'm getting a bit frustrated trying to figure out what is going on here.