SM_ATL

Part 1

I do not mean to light a fire for nothing, but I got increasingly concerned by what seems to be a lingering issue with change over valves in the 991.

Here's a picture of the part in question (the part number is 7PP906283B, now replaced by 7PP906283C):



Based on a quick research on the internet, it looks like Porsche was aware of the issue for early 2012 builds and that launched a recall campaign (WC-43) intended at replacing 8 of these valves.

In my case, my sport exhaust stopped functioning and 3 out of the 4 change over valves I have checked were bad (I did not check the others).

There are also various threads about 991's built at different times that have had heating/cooling system issued. Again, the same part was the culprit.

I find it intriguing that it has been going on for so long and that Porsche has apparently not resolved the issue.
The first concern I have is that you may not always detect that something is wrong: it is only when my sport exhaust stopped working properly that I discovered it, but the valves controlling the symposer and the intake flap were already bad. The second concern is that I read that this part would be used in more critical components (PDK).

Change over valves (simple solenoids in fact) are a very common part and Pierburg, the manufacturer, supplies it to a lot of car makers, including for the previous 911 models. This part number is specific to the 991 and seems to be the one having an issue. They may not be sealing properly allowing moisture in, causing the valves to malfunction over time.

I am not posting this to alarm you but to keep this in mind and report if you had other issues resulting from the failure of that same part.
Having already had 3 bad solenoids, I intend to drop the car at the dealership to get it checked.

SM_ATL

Change Over Valves failure - part 2 I found the following schematic about the vacuum system in the 991 Service Information book (you can buy it from Suncoast BTW):



It confirms my fear that more critical items can go wrong due to failed solenoids: i.e. shut off valves for engine coolant or ATF (= automatic transmission fluid for PDK). The Porsche document nevertheless mentions that "electric solenoid valves in the vacuum system are fully diagnosable (short circuit/open circuit); electrical faults result in an entry in the DME control unit and the PDK unit". I nevertheless did not get any alert for my failed solenoids and will definitely get the other ones checked ASAP.

neanicu

I understand that the one for your PSE was bad because it stopped working,but how do you know the rest were bad?
Also,having an electrical circuit to activate or deactivate them,most likely there will be a signal wire coming directly from the PCM. If one of them goes bad,it will not send the correct voltage to the PCM,in which case a fault code will be set. How did you or the technician figured out the electric change over valve for the PSE was bad and not something else,since no code was set?(besides the obvious-that you couldn't hear a difference with PSE activated)

SM_ATL

-WhenI had PSE, I was basically in loud mode all the time. I then got an aftermarket exhaust (AWE Switchpath, very happy with it) and started to use the quiet & loud mode and noticed at some point that the exhaust was stuck in loud mode. Possible explanations were: 1/ failure of the exhaust valves (they were fine) 2/ disconnected or molten vacuum lines (they were OK) 3/ engine vacuum pump not working (checked that it was fine) -> 4/ the only remaining explanation was a failure of a solenoid.

-Solenoids can be easily tested: you remove them and apply 12V voltage and simply listen if you hear a 'click' indicating that the solenoid is functioning (a simple 9V battery and 2 wires is enough to build a DYI tester; I also double checked with an actual 12V source and using an OEM connector and got the same result).

I then did some research on 991 forums and found out that failed solenoids were the cause of similar problems for a bunch of forum members.
One more thing that tipped me off is that when I asked the dealership if they had that part in stock they actually had 4 of them available. According to a tech, this is something that they typically do not have readily available and order from the Porsche warehouse. The fact that they keep it in stock at the dealership is one more indication that there is an ongoing issue...

neanicu

I guess we can go back and forth on this all day...it will throw a fault code. Do you have PIWIS to check for faults?
These electric change over valves might be more complex than the same principle purge solenoid valves found in the fuel systems.
They are definitely influenced by vacuum(the vacuum at idle is not the same with full throttle or anything in between). Should hold vacuum and when voltage is applied they should open.
How do you know the PCM is providing 12V all the time? Do you have a wiring diagram? Changing parts because you " think " they're faulty or because the dealer does not have them in stock is not the way to go...

SM_ATL

This is NOT how it happened.
I started by researching similar issues and found a large number of relevant cases where Porsche recognized the issue and replaced the solenoids.
I tested them myself and then got the car double checked by an indy who is a former Porsche tech. Solenoids were mechanically stuck and it wasn't a matter of voltage applied or vacuum level.

The point of my additional comment about parts being in stock etc. is that several dealerships tend to deny that there is an issue or even claimed that there was never a campaign about this (there was: WC43: replacement of all 8 solenoids).

You do not have to believe me or consider I am not competent enough to make these statements, so be it.

neanicu

Please do not take my post the wrong way...I am not trying to challenge your statements past my knowledge and I do admit I am not particular familiar with this system in case.
I am merely trying to understand technically how is it possible for a number of units to be faulty in the same system and not trigger a fault detectable by the PCM.
Yes,there is a possibility to be mechanically stuck,but to not trigger any kind of " red flag " in a modern complicated computer controlled system is what makes me suspicious... If the valve doesn't open when the computer supplied the necessary voltage and command it OPEN should automatically trigger a fault...but I'll definitely take your word for it and admit it is possible...
Glad you had it figured it out and hopefully many will benefit from your advice.

Noah Fect

It sounds like they are designed to apply either atmospheric pressure from the intake or vacuum from a dedicated pump to a mechanical actuator, based on the solenoid position. Is that the correct interpretation?

The advent of "coast mode" has probably brought an end to the practice of using manifold vacuum for anything important.

neanicu

I wish I had an answer how the particular ones in the 991 work,but I don't...
Maybe SM_ATL can chime in...
Judging by the diagram he provided in his initial post,it certainly seems a " Mechanical vacuum pump " is involved...

CSK 911 C4S

I just had one replaced on my 13 C4S today.

It tossed up a coolant system failure message on the MFD.

All gauges read correctly and no over heating noted... did find that I had no heat when I tried to take the chill out of the cabin one morning.

The tech did say the system fails in the "safe" mode so as to not cause damage to any components. Time will tell when more die.

BTW they have a box of them on the shelf in the parts department.

StudGarden

^ I wonder how much these will cost to replace out of warranty if its still an issue.

CSK 911 C4S

Doing a quick search the part is $42.

Finding which one is faulty is the trick. The tech said it was a generic fault for the system and doesn't identify which one took a crap. Once I told him I tried the heat he knew exactly which one to pull and test.

Fortunately for me my 13 is a CPO car so I have 88,000 miles left on my warranty.

STG

How many of these do our cars have?

Same part # for all?

Anyone have locations of them on the car?

Amazing the issues that can be caused by all the things these things control.

Thanks

duxsi

The number of COV's depends on if you have PDK or MT.
I believe (from a bad memory) that PDK's have 8 and MT's have 6 CoV's.

STG

I have PDK. Duxsi, nice to see you on the board! Been a while. Having some work done on my car and wondering if I should just change over to the lastest versions. My car is a 2012.5

I know some got changed as part of a campaign already at some point.

Curious what version they're on now. Might call Sunset and find out.