Porsche 981 Engine Overheating Error! Temperature Sensor?
Burning Brakes
Joined: Jun 2016
Posts: 1,222
Likes: 564
From: SF Bay Area
Yes. It doesn't really work effectively if there's liquid in the system. Also it'll spray coolant out the tool's exhaust and make a mess.
That said, I don't own a 981, but my understanding is that the proper 981 coolant bleed procedure requires using PWIS either during or after the vacuum fill. This is different from the 987. Not an expert here so you may want to verify.
That said, I don't own a 981, but my understanding is that the proper 981 coolant bleed procedure requires using PWIS either during or after the vacuum fill. This is different from the 987. Not an expert here so you may want to verify.
Rennlist Member
Joined: Jan 2016
Posts: 3,563
Likes: 779
From: On a pygmy pony over by the dental floss bush
Yes. It doesn't really work effectively if there's liquid in the system. Also it'll spray coolant out the tool's exhaust and make a mess.
That said, I don't own a 981, but my understanding is that the proper 981 coolant bleed procedure requires using PWIS either during or after the vacuum fill. This is different from the 987. Not an expert here so you may want to verify.
That said, I don't own a 981, but my understanding is that the proper 981 coolant bleed procedure requires using PWIS either during or after the vacuum fill. This is different from the 987. Not an expert here so you may want to verify.
Banned
Joined: Mar 2011
Posts: 10,084
Likes: 1,207
From: Spring Lake, NJ, US of A
Yes. It doesn't really work effectively if there's liquid in the system. Also it'll spray coolant out the tool's exhaust and make a mess.
That said, I don't own a 981, but my understanding is that the proper 981 coolant bleed procedure requires using PWIS either during or after the vacuum fill. This is different from the 987. Not an expert here so you may want to verify.
That said, I don't own a 981, but my understanding is that the proper 981 coolant bleed procedure requires using PWIS either during or after the vacuum fill. This is different from the 987. Not an expert here so you may want to verify.
Rennlist Member
Joined: Jan 2016
Posts: 3,563
Likes: 779
From: On a pygmy pony over by the dental floss bush
No REST feature on 981 cars that I'm aware of. I didn't do any setting of heater or defrost controls from what my car is normally set at, and the ignition was off, so it wouldn't have mattered anyway what the settings were. I believe the concern about needing PIWIS is due to the DME-controlled coolant valves in various places around the vehicle. I assume either the flow control valves aren't completely water tight or they default to open with power (engine vacuum and electrical) off. Whatever the case, when you are allowing the coolant to be sucked back in during the fill portion of the vacuum coolant fill procedure, just let it sit for a few minutes after it first appears the coolant has stopped flowing into the car. There will be no issue according to several shops that do this with 981 cars (vacuum fill, no PIWIS) as a daily part of their business, and according to my experience (albeit a sample of one 981 car).
Track Day
Joined: Nov 2025
Posts: 17
Likes: 2
From: Kerrville, TX
FWIW...I just went thru some of the issues you have encountered with a coolant change, and after numerous start, warm up and cool down cycles, I was finally able to get those annoying air pockets out of the system. I noticed during this process, the ventilation heat would come and go.....now that the coolant level has stabilized, coolant temps have stabilized and ventilation heat is now stabilized as well. I too was aware of the vacuum refill tool and used it, but I don't think I was able to get enough vacuum and ended up with air pockets. I know from experience what a PITA it is to drain and refill the system, SO, my advice would be to continue with the heat and cool down cycles and see if the blockage to the heater core will eventually be bled out before you resort to another drain/vacuum/refill. Make use of the inline bleed valve until you see some positive results on the vent heat issue. Hope it works for you...maybe I just got lucky. I'm from the "old school-air cooled Porsche" club and still learning about these new fangled water cooled P's.
I just now see where you originally posted this subject almost 5 years ago.....you have likely solved the problem by now or given up. Anyway, maybe our collective experiences on this issue will be of some use to the next person who encounters this problem.
I just now see where you originally posted this subject almost 5 years ago.....you have likely solved the problem by now or given up. Anyway, maybe our collective experiences on this issue will be of some use to the next person who encounters this problem.
Last edited by ttu1970; Dec 5, 2025 at 03:34 PM.
