Copilot

First time poster in this forum! Starting this thread to both seek help and also hopefully document the fix.

Driving to dinner with the wife the other night, got a "coolant low, refill immediately, do not drive on" warning. Stopped (thinking it was probably a faulty sensor as I hadn't noticed any leaking), and sure enough - low coolant in the reservoir. Filled it up with water to get back home (probably 24 oz or so, thank goodness we had some water in the car) and by the time we got home it got the warning again, with some noticeable coolant coming out the bottom of the car. Pretty strong coolant smell too.

Did some basic diagnosing and lightly pressurized the coolant system with a coolant system tester and found that sure enough, I have about a 3/4" crack in one of the ends of the "Y" on the engine coolant vent line under the intake manifold. I pulled the panels off the bottom and found that the coolant was basically dripping down off of one central point, right at the bottom of where the bellhousing connects to the transmission (and seemingly dripping down through it). I've attached a picture of the leak at the bottom for reference. The coolant vent line is obviously cracked and needs to be replaced, but it also doesn't seem like the type of crack/leak that would cause that significant of a leak that quickly - which makes me concerned there may be another leak that I haven't discovered. I've not found a lot of info about main coolant leak sources on the 3.6L V6 TT motor... lots of stuff about the 958.1 V8 rear coolant line, but I have no idea if the V6TT has the same issues or not. If anyone has any ideas or guidance, I'd be grateful for the insight.

I'm going to go ahead with replacing the engine coolant vent line, but am kind of winging it because I haven't been able to find any good repair manual sources for the 2016 GTS (AllDataDIY stops at 2015). If there's a good source for purchasing accurate repair manuals, let me know. While I'm comfortable enough figuring it out on my own and am reasonably mechanically skilled (previously rebuilt a 996 3.6L engine and swapped the V8 on my old 2004 Cayenne when the first engine died), it always helps having a checklist/guide/torque specs to go off of.

Thanks in advance!

RAudi Driver

The only thing you'll need the manual for is tool list, bolt tightening sequence and torques. Not too familiar with the 2016 Gas but if it's anything like the 958.1 turbos where the turbos are down on the sides, getting into that valley should be a piece of cake.

BrendonSF

How many miles are on your GTS? Might be worthwhile to overhaul all of the piping while you've got the manifold off. I had a leak on my '16 GTS in there as well and spent about $3k at an indie shop for a full system overhaul. Around $1,800 of that was parts if memory serves right.
I recall reading about one other GTS (similar year, similar mileage) recently reporting the same issue. The reality is that a cooling system refresh at 100k is typically pretty smart preventative maintenance.

Copilot

Just a touch over 70k on the mileage. Good call - I'll take a look at everything when I get the intake off. Probably goes without saying but i'll at the very minimum be draining/flushing the whole coolant system.

Also, I realized - the 2016 GTS shares the same engine as the Macan Turbo, correct? AllDataDIY has the manuals for the 2016 Macan, so I may just grab a one month subscription since all the engine instructions and torque specs should be the same.

Eyeballing it, it really just looks like the only "complicated" portion of removing the intake is disconnecting the fuel lines from the rail/distributor running over top. Looks like a different/newer style connector than past Porsche engines so I have to buy a couple of fuel line pliers but with the right tool looks like it shouldn't be too bad. That, and looks like I have to disconnect about 15 different sensors.

BrendonSF

Yeah, same engine as the Macan Turbo. It's involved, but doesn't look like rocket science.

Copilot

Update on the leak:
It's fixed! After everything, it does look like it was just the coolant vent line, nothing else leaking. Like many things Porsche, many hours of labor to replace a $60 part...

Overall, it's not the easier job, but not the most frustrating. I ended up finding the following DIY on a Macan forum that helps with most of the procedure: https://www.macanforum.com/threads/c...cluded.173262/

There's a differences w/ the Cayenne GTS/S that I think are worth noting:
First - safety - disconnect the battery completely unless you want a serious fire risk. In step 3 below, you'll see I mention removing a fuel line. It's right above the starter. If you're an idiot like me and you forget to disconnect the battery, you might accidently touch a tool to the starter and create a spark/arc near an open fuel source. It was incredibly stupid of me to forget to disconnect power, so don't be like me.

Modified Cayenne GTS/S steps:
1. For the intake plenum, there are four bolts/studs on the throttle body that this locks onto. You don't need to remove the bolts at all to remove the plenum; just disconnect the hoses attached to the plenum, release a catch tab on the drivers side of the plenum, and then rotate a quarter turn. It then pulls right back. Pretty easy/smart design.
2. There is come kind of fuel line/distributor type harness over the top of the intake that the Macan doesn't seem to have. While you could disconnect the lines to make it easier, it appears to need some special tool beyond normal fuel line pliers. I opted to just unbolt it from the intake and then remove the intake from underneath.
3. Underneath the intake, there are two solenoid valves, a aluminum fuel line crossover between the fuel rails, and the secondary air pump. Disconnect and remove the fuel line.Unlike in the Macan procedure, I didn't fully remove these, I just unbolted them, disconnected the wire and then move them to the side. The bracket they are attached to is connected to the engine with three torx bolts. These bolts need to be loosened so you can move the bracket, but you don't need to fully remove the bracket to pull the coolant vent line out, you just need it to be loose enough to maneuver the line out.
4. The Macan procedure talks about removing the engine wiring harness cover. Don't bother. Getting the fuel line disconnected from the hose/hose clamp behind this assembly is incredibly difficult, even with a remote/flexible hose clamp tool. So instead, I just cut the bad coolant vent line at the point where it passes behind the wiring harness, which allowed me to pull the rubber coolant hose that it connects to out from behind. Then, I was able to attach hose clamp pliers and remove the nipple. Then for install, you can open the hose clamp with a set of remote pliers, maneuver the hose back down behind the harness, and connect.

Install is pretty simple, the traditional "reverse of removal". Key torque specs are 10 NM for the intake manifold bolts. I've attached an image of the bolt order; but it's pretty common sense. Additionally, I replaced all the intake manifold and throttle body seals. Not a major cost, maybe $20-30? FCP Euro sells a kit.

mistermct

So I just went through the same process, this is a great write up. Took me several hours as this was my first time working in this engine bay. I took a few photos of the broken coolant line to share.. the failure mode is alarming as the tube and part going into the head are basically disintegrating. 50k miles.


Split coolant vent line

Copilot

Nice job getting it fixed. Mine split in exactly the same place and exactly the same way. I don’t know if I mentioned mileage, but fairly low on mine too - 78k miles when I caught it.

Of course, the car was back on the road running for about 2 weeks before the brake pad lights went off 🤦‍♂️

mistermct

I've found one other heat related issue.. the radiator shutter servo has failed. Interestingly, I can move it by hand AND it closes at speed (80-100mph). Not impressed with that that failure state. No CEL just an error code "calibrate servo" and "implausible state". I've zip-tied it open after discovering speed closes it. I'm curious if your servo is functional? Maybe excess engine bay heat is prematurely aging some of these plastic parts? I'm probably stretching but I thought worth sharing and discussing as this failure seems to becoming more common.

BrendonSF

I had my cooling system rebuilt at 105k on my '16 GTS, and at that point my servo motor was also making some strange noises, and had it replaced then. Cheap part, but labor wasn't cheap. Pretty sure there is a DIY on here somewhere. Though the shop told me they had to program/calibrate the motor; not sure how important that is though.