Repair of Second (Zone) Blend Door Through Heater Core Housing

This week, I committed to repair the blend door foam problem with my Boxster 987. I researched everything I could find online and set about repair of the primary mixing blend door based on the method through the heater core housing documented on this forum, YouTube, and elsewhere. That repair procedure addresses just the primary temperature mixing blend door only. However, I really wanted to repair both that door and the zone blend door through the heater core opening without removing the dash. Since the 987 has dissimilar vents from the 986 , repair by cutting the ducts from the cabin was also not feasible. After some trial and error, I was able to repair, fairly easily, the mixing door with the following procedure. I only have pictures of the process after removal of the primary mixing blend door. Supplies: Blend Door Plugs The Original DSP Blend Door Foam Fix for VW Golf Jetta Beetle Passat | eBay RTV Gasket Makers & Sealers | O'Reilly Auto Parts Blend Door Cap The Original DSP Blend Door Foam Fix for VW Golf Jetta Beetle Passat | eBay Foam Tape Neoprene Foam Strip Roll by Dualplex, 2" Wide x 10' Long x 1/16" Thick, Weather Seal High Density Stripping with Adhesive Backing - Weather Strip Roll Insulation Foam Strips Borescope: DEPSTECH Wireless Endoscope, IP67 Waterproof WiFi Borescope Inspection 2.0 Megapixels HD Snake Camera for Android and iOS Smartphone, iPhone, Samsung, JB Weld epoxy for plastic: https://www.amazon.com/J-B-Weld-50139-Plastic-Adhesive/dp/B01IBOK7FE/ref=sr_1_3?crid=3VKVEYPZRE9Y2&dib=eyJ2IjoiMSJ9.uP1OR-u0w1YPIVc3F1cSrRR3UXteTt5-ge4Kbom-Yt_unr-2REGCGHZsqYiC6qIFsrqpFp1YgHT7U4nmOLaNGD_vY1UmbHCyWfmERC3y7wbkYeiiq5wZnUj4WO7TZ0UVaBqho3RNW1ffyss5OL14CSXubmE6HuFg_xmqM-JIJkGg3c4TTGGhf79vdApTyzJ4RqHRI38Ebm7w4O8OkGFpB9uBxAOzBBBEdvHgBnf5APc.iCMN-GZvVnCmJQBD0JnWbclKjPm3M1YfEDO91KoYCTI&dib_tag=se&keywords=plastic+weld+epoxy&qid=1736165231&sprefix=plastic+weld+epoxy,aps,167&sr=8-3&th=1 Course drywall screws: Grip-Rite #8 x 2-1/2 in. #2 Phillips Bugle Head Coarse Thread Drywall Screws 1 lb. Box 212CDWS1 - The Home Depot Steps: 1: Power up the car electrical system and put the climate control selector to middle vent position. This will put the zone mixing door in a position aligned with long axis of the car 2. Utilize the instructions on this very informative video to remove the heater core and temperature mixing blend door: 3. Reach into the heater core housing with your left hand (palm facing aft) and extend your fingers into the opening going towards the passenger cabin. You should be able to feel all four oval cutouts in the zone blend door on the left side (drivers side for North AmerIcan models) of the car. 4. Take a course terry cloth hand towel and wipe the remaining foam from the blend door. My door was easily cleaned due to the age of the foam. Check that the blend door is free of foam using the borescope. 5. Using an oval plastic plug from the kit, insert drywall screw ( FINGER TIGHT) into the plug offset from one side. Coat the plug with RTV. 6. Place the plug with drywall screw between your fingers, extending palm upward ( NOT as depicted in the image above). LIKE THIS: Reach into the opening and slide the plug into the oval cutout in the door. If you drop the plug accidentally like I did, you should be able to retrieve it using a magnet tool. Repeat for all four plugs. 7. Remove the drywall screw using your fingers. The oval properties of the plug will prevent it from turning as you do. If the screw is too tight to turn by hand, move it from side to side and up and down while pressing against the blend door. That will enlarge the screw hole enough remove it. 8. Repair the larger temperature mixing blend door and install it. I used a combination of plugs and foam tape. I also elected to epoxy a new plastic plug to the upper pivot point. 9. After the RTV cures, reinstall the battery temporarily to power up the electrical system and check that the doors move correctly by selecting temperature and zone settings on the climate control panel. Once again, the borescope can be used to view the smaller door. ZONE DOOR FACING AFT: 10. Put the car back together and test the system. Thank you, Joe

I will give this a try sometime soon! Thanks for posting this. I am curious if 3d printed plugs with small magnets installed (and an opposing holder tool) would be enough to hold them for install.... David

Hi David, The magnets might be a completely viable option. I had many frustratingly failed attempts at this door until I figured out that aligning the blend door with the long axis of the car is key to successfully getting the plugs into position. I dropped a couple down into the duct and also found they could be retrieved with a pickup magnet tool through the floor vent opening under the glove box. Joe

Is the repair working propertly without any issues? I think there were some discussions around the door(s) being "heavier" and that's why Porsche engineers placed / attached flimsy foams..... Just wanted to double check before I go down the same path.

My own story regarding the disintegrating foam is very different. Not having the capability to fix it myself, and not inclined to pay a lot of money to those who are capable, I simply put up with it for about 6 months or so and it finally stopped. I'd vacuum out my air vents and interior every couple days along the way. It's been almost two years now since it stopped and I am unable to discern any difference in how the AC ,defrost, or heating system works or sounds. As far as I am able to tell, the systems still work as before. Since I live in Florida, that's my experience. Perhaps in a colder climate there may be some noticeable difference but not here. And at this point, there's no plan to fix anything as I'm unable to anticipate some kind of payback.

Having delved into this on a previous 996, and reading about other methods and solutions to the foam problem, I agree that the issue of just letting the foam fully disintegrate is not as much of a factor in warm climes. (I’m in Florida, also) Wish I took photos of my fix, as it was 6-7 years ago, but I was able to pull out the head unit, cut an opening into the ducting/plenum and after scraping away the remaining foam and vacuuming out the debris, I used thermal foil tape HVAC guys use to seal heating duct work. The results were more than satisfactory.

WTFChuck... Assume that was a 986 ? Different story in a 987! David

Sorry for the confusion, but it was a 996, ( 911 Carrera ). I referenced that repair to agree about the lesser importance of the loss of foam in warm climates. I remember reading some time ago that for anyone living in colder conditions where a warm car is needed, the repair becomes more necessary. It wasn’t a fun job, but I was grateful for the access through the opening for the head unit. Wouldn’t want to do it again.

Hi, 987.1 2008 Boxster S So I did the two blend doors through the frunk job. I will say it is a pain. Takes patience, but in the end can be done. I started with what the OP says ... good general direction. I think the borescope type camera is needed. On the inside passenger side footwell bearing (the fastener that holds the cover up is a screw... so unscrew it (it looks kind of like a push in type...)) after removing the actuator lever, thread the screw back in and pull it out with pliers.... as it kind of snaps in. Pro-tip.... maybe stuff towels around the area when removing the upper door bearing... if it flies loose into the dash it can take a lot of time and effort to find and retrieve! I did several things... -I made some tools I thought may work.... custom 3D printed door plugs for the 'buried' door with a tool with pins and magnets for holding... the pin/magnet concept worked well, but the location was a bit more 'around the corner' than I guessed so I ended up making plywood extensions to reach back... If there is interest, I can post the 3D printed parts.... but don't have time to do the 'plywood' parts right now. -My foam was all loose and failing, but the plastic tape layer was 'hanging around' stubbornly if loosely... I used a coat hanger passed through a bent brass tube to go around the corner and scrape and hook the plastic to drag it out... also used a shop vac adapted down to a small (~1/2 to~3/4") tube to grab some of the plastic and foam.... all looking through the borescope. -Used RTV type glue to install the plugs.... that part was not really too bad. Was helpful having a second set of hands to align/jiggle and inspect when re-installing the removed door. I have air out of the correct vents, cold AC, and NO FOAM! Nice. David

When I see pictures of any of these repairs being made, I get somewhat confused. The original foam appears to have let some air penetrate the system through the foam, right? At least that's the impression I get from the appearance. Fixes for the most part, appear to fill those same holes with solid closures which blocks the air completely, right? Again that's the impression I get from appearance. Blocking those holes completely would result in a different air distribution than original, right? Maybe I'm off base here but the repaired system with completely blocked holes is different than the system design, right? Thoughts are appreciated. Thanks.

Seems most of the foam blew out of my 2010 years ago. Since then I rarely see a chunk stuck in the vents, which a shop-vac takes care of easily. My car spent most of its life in Florida, where the heater was not so critical. I can recall having a few issues with windshield condensation during the summer, but it was so minor that a flick of the wiper did an adequate job. Now that I'm in the mountains of N Carolina it is even less of a problem. Summers, while humid, are pretty moderate and I garage it most of the winter. These days, I'm choosing my battles and this isn't one I'm obsessing over.

On the plastic film between the two layers of foam - is it possible that was the adhesive layer on the side of the foam that attached it to the doors? My thinking was these existed to allow some air to continue to flow through as the doors change position so there wouldn't be a pressure buildup on the upstream side of the door - the pressure buildup could help or make worse the movement of the door - making more work for the actuators. Just my theory - yours is just as good but I like mine.. If I was doing it - I'd probably cover up most of the vent surface with the traditional aluminum tape, and then think about putting some less dense foam in the area the tape isn't covering. And try to find foam that won't melt down like this stuff does. It reminds me of the foam that loudspeaker surrounds are made of.. when it goes it gets really sticky and ugly.

David, Nicely done! That is a way more elegant solution than using drywall screws. I need a 3D printer ! i have enjoyed my repair. In the Mid-Atlantic area it has expanded our top down days with chilly temps. There has been a noticeable improvement in the zone control especially heat through the upper vents. When I started this thread, I didn’t intend it to be a statement that anyone SHOULD accomplish the repair. It was there to allow those considering the second blend door repair the ability to do so without removal of the entire dash. Also, a complete factory spec repair with original foam was beyond my capabilities. i agree. This is not an easy job. Again, well done! Joe

Thanks Joe, and thanks for showing what is possible on the 987/997. I am not sure my hands would have been able to do the drywall screw technique, so my hats off to you for being able to do it. Agree the point is not who should do it... it is that it can be done (and some info) if you want to. David

I am getting ready to print the plugs from what I am gathering I need 11 small circles, 6 medium circles, and 4 of the big ovals for my 987.2 from the Ebay link? Am I correct in this?

That’s correct. You will have a couple of extra plugs if you buy the ebay kit, as I remember. I was also glad to have ordered the “ cap ” for the pivot end on the heater core housing (the one that you saw off). The ebay supplier was in the UK, but it shipped quickly. Good luck with the repair! Joe