Clearing the HVAC drain
 

This is copied from another thread - and I had no photos when I wrote it. I borrowed a few from other posts. I will be doing the annual HVAC drain clearing and HVAC filter change shortly - and will try to remember to take more photos at that time to add to this. Meanwhile.. this should be enough to get people started.

The overflow is from the gasket around the cabin filter. Water will drip out as it soaks the bottom 2" of the cabin filter.

Before pulling the hose out you must:

1. Remove panel under the glovebox. One torx screw. Disconnect the lights/socket so you can move the panel out of the way.

2. Remove footwell vent tube. Pull straight down toward the right side of the vent. It has a plastic clip that goes over a plastic oval nubbie on the body. The left end is simply a push fit into the vent outlet in the HVAC box.

3. Get the cabin filter out. On a 955/957 it's a headed self-tapping screw. I seem to recall buying a special socket for it - probably 5mm. Remove the screw, then reach up with your finger past the end of the door and pull the catch gently back. On the 958 there will be no screw - just the catch - unless the catch has broken and the screw added (that's an official Porsche fix.) Be prepared for a deluge of water (I used a broiler pan to catch it - about a quart..) Put the cabin filter aside to dry out, or throw away and replace (recommended.)

4. Standing on your head (not really, but it feels like it) remove the bastard clamp that holds the drain hose to the HVAC housing. A mid-sized channel-lock seems to be the best tool. Squeeze the two ears on the clamp, and move it down on the drain to where the drain isn't over the water outlet. This should be obvious when you see it. On the 955 I owned there was no clamp. I doubt if a clamp is needed unless you have passengers who like to stuff their toes up under the bottom dash panel and push the hose off the HVAC box. I assume that's why Porsche added a clamp.

https://cimg8.ibsrv.net/gimg/rennlis...3e1eb29b90.jpg

Borrowed from a post by ocmacman (thanks!)

https://cimg3.ibsrv.net/gimg/rennlis...0a0c8564b6.jpg

Bastard Clamp!


5. Pull that end of the hose off the outlet in the HVAC housing. Be prepared for another quart of water. Have something to catch it in.

6. Pull back the carpet near where the hose goes through it, and grab the large round flange on it and pull it toward the rear of the car. It will pull out of the firewall. It has a flapper closure at the end - chances are that's stuck closed from munge or spiders.

7. Clean the inside of the hose. Then consider removing the flapper. I didn't, and I'm still thinking about it for next time. Is it better to have a flapper that might stick, or to invite bugs up into the HVAC (I have mud-wasps around my house - they're always looking for something like that to build a nest in..)

8. Reinstalling the hose is easy - except for the bastard clamp from hell. Push it back into the hole until the grommet on the end seats in the firewall opening. The big rubber flange goes behind the carpeting not outside the carpeting. Then wiggle the other end back on the fitting on the HVAC box. If the clamp is there - reinstall it I guess. Or take it off and throw it away. Your choice.

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Next you have to mop up the water in the footwell. Using your plastic trim removal tools (you have these right? If not - visit Harbor Freight, identical to the ones the parts places sell, but 1/8th the cost..) You can sort of pry the edge of the carpet out from under the door sill guard. I would love to talk to someone who has removed the door-sill guard, since it appears to be part of the kickplate on that side of the footwell, and it doesn't look trivial to remove.

Lots of towels and big sponges pushed under the carpet will help dry it out. Leaving it propped open for a few days will help it dry out.

Be prepared for cuts/scrapes and bruises. Using the AC will actually speed up the dryout time since it dehumidifies the air helping the water to evaporate, and go out the HVAC drain like it should have to begin with.

Good luck. It's not a complex job, just awkward working location and that damn clamp.

This video should help

I have a 958. Do not pull the tube out of the firewall (like I did). It's very difficult, if not impossible, to reinstall the grommet so it seals properly without pulling the carpet for better access. There's about an inch or more of carpet and padding hindering access to the metal firewall that the grommet snaps into. It's like pushing a wet noodle. Better to blow, push with a pipe cleaner, or suck debris out from the clamped end. You can also crawl under the car and reach up to clear debris from the end that protrudes through the firewall.

I pulled mine out last year and reinstalled best I could. I should have reached up from underneath the car to check that the end was protruding, but I didn't. Now I have a wet carpet drying in my living room. I haven't pinned down a leak, HVAC drain was clear (obviously), cowl drains are clear, rear washer hose is ok. So, until it rains later this week, I'm going with the assumption that my HVAC drain tube didn't make it through the hole when I reinstalled it *or* some water splashed in through the hole because the drain definitely wasn't snapped into the firewall and properly sealed. While my carpet was out, I reinstalled the HVAC tube properly snapping it into the firewall. Even without the carpet and padding in the way, it was still very difficult to install.

It is a bitch to reinstall. You can't push it back through from the firewall.

I removed the passenger side hood strut and snaked my arm down behind the engine to work it through. It took some doing and my arm bears the marks from the effort - it's a VERY tight fit! - but I got it through and sealed in about 10 minutes, once I figured out how to get my arm down there.

Hopefully, that's what was causing my water leak. I'd hate to think all the scratches and cuts were for nothing!

Funny - I did. The trick is to pull the carpeting away from the hole so you're facing the bare metal of the firewall, wet the part going through the hole (a bit of soap makes it even easier) then compress the lump on it inwards, closing down the drain passage and push. Once you have one spot under the lip of the hole, continue compressing and working it into the hole until the entire thing is seated in the hole. Took about 5 minutes, and I was doing it in a motel parking lot while we were on a trip.. The hardest part of the job is the bastard-clamp (see the first post here) which somehow :icon501: has gone missing on mine. The firewall photo in the first post is borrowed, but it shows the area with the carpeting pulled down and out of the way. The rubber membrane on the firewall is only about 1/8" thick, and there is a hole cut in it where the drain goes that is about 1" larger than the hole - so you can get to the edge/lip of the hole.

Mods - can you add this to the HVAC Drain DIY (or delete this if it's not useful)?
 

I had the HVAC drain issue in my 2014 Basic B*tch Cayenne this week. We plan to sell the car in less than four weeks when my Macan (hopefully) comes in. So, I checked out the DIY thread and girded my loins to deal with The Bastard Clamp (TBC). GREAT GOOGLEY MOOGLEY - I hate that clamp, and trying to position lights in there so that my old eyes could see was also a pain. I futzed around with the channel pliers for probably 20 minutes before I changed my approach.

I am posting this because I think I found a way to make the clamp less bastardy. You need your channel pliers, a pair of vice grips, and the right size zip tie (not too big, not too small - see the third picture below).

- Loop the zip tie around/under the "wings" of TBC (see first pic below)
- Use your channel pliers to squeeze the clamp with one hand while you pull the tie to tighten the zip tie with the other hand (this is easier than it sounds)
- Tighten it as far as your can. You will likely not be able to tighten the zip tie enough to eliminate the need for some sort of pliers to finish the job. If you do, that's awesome.
- With the zip tie about as tight as it will go, clamp on the vice grips as shown in the second picture below and push TBC back towards the firewall. Then you can follow the awesome instructions from the DIY.

The purpose of the zip tie is to create the ability to use a pair of medium-small vice grips to finish the job of pushing the clamp back towards the firewall (and pulling it forward, back into place. Maybe just a pair of vice grips would have been all I needed, but I could not get everything to clamp properly with the vice grips until I limited how wide they had to initially open (so they could close down far enough).

Yes - I have dogs with short hair. Why do you ask? :)

https://cimg1.ibsrv.net/gimg/rennlis...b9b978e524.jpg
Start with your zip tie positioned like this, and use the channel pliers to squeeze the bastard clamp with one hand while you tighten the zip tie with the other.
https://cimg0.ibsrv.net/gimg/rennlis...1650e8135d.jpg
With the zip tie as tight as you can get it, lock on some small/medium vice grips and push the bastard clamp back towards the firewall.

https://cimg7.ibsrv.net/gimg/rennlis...3656ee213d.jpg

I can’t understand why everyone with a base Cayenne removes that valve unless its full of water and you need to drain the area around the cabin filter., On the VR6 it can be reached by hand using a flashlight, but you do need a step stool. As an alternative, I use a coat hanger and a flashlight and give the flapper a flick and poke around inside it every 6 months. It will never plug again. This preventative maintenance takes 2 minutes. I’ve had the swimming pool on the floor and R&R that valve...never again for me. This of course doesn’t work on V8’s, no room.

I am still drying out my car, three hours after I drained out a bunch of water (mostly on to towels and my rubber mat), then cleaned out and blew out the line. My new cabin filter is on order. I knew to do this because I followed somewhat normal logic:
1 - I had a problem with water draining into the passenger footwell
2 - I searched and read the forums, which led me through diagnosing my problem
3 - With the problem determined, the DIY section showed me what to do
(since I service my car at the dealership, I expected THEM to be do the preventative cleaning - now I know I have a lot more to do, thanks to this site).

I thought I could help others with this problem, but that DIY thread is closed, so I posted something here with a title that I hoped would catch the mod's attention, so they could add it to the other thread.

Also - for the record - anyone who wants to avoid this problem (or try unclogging the line the easy way, first), this is the flappy valve that needs your regular love and attention. It's up against the firewall on the left side (think about where your toes in the footwell would meet the firewall). If you just look down the left side of the engine, then down and further left on the firewall, you can't miss it (with good lighting). I didn't see a good picture from this perspective anywhere (apologies if there is a picture out there).

This is covered elsewhere, but if you've got a clogged HVAC drain line, your cabin filter is likely soaking wet and needs to be replaced. Check the DIY threads for that.
https://cimg4.ibsrv.net/gimg/rennlis...c248b11be6.jpg
Clean me!

I'll add this thread to the DIY..

One way to avoid the hassle of putting the bastard-clamp back on - is to buy the correct tool for it. Channel locks are sorta close, but there is a tool made specifically for that horribly designed clamp.

The other way is - don't put it back on. I didn't. It's in the spare tire well now. The hose has not come off. My '06 955S didn't have the clamp - I assume from the factory, or from someone else removing it and not replacing it and it never came off. It would take quite a bit of toe-play to get a toe up where the hose is and dislodge it. Mine hasn't. Been about 20,000 miles since I tossed it in the trunk.

And I guess one could also simply install a normal screw clamp - made to be operated by human beings with a screwdriver or nut-driver. Harbor Freight has kits of them for small money, more than adequate for this use.