Here’s Why Your Car Might Pelt You With Little Bits Of Foam

Imagine you’re driving down the road and you get hit in the face with a small, soft object. Then another one. Then another one. It’s a particularly unusual situation because your windows are up, your sunroof is closed, and as far as you can tell, you’re the only person in the car. You manage to pick up one of these pieces of debris and realize they’re little bits of foam coming from deep inside your dashboard. This isn’t the sort of foam party you were expecting, right?

It’s easy to take your car’s heating and air conditioning for granted. After all, heat in a combustion-powered car is just a byproduct of igniting gasoline vapors, and air conditioning is one of those things that just makes life easier. However, it probably shouldn’t come as a surprise just how many parts are needed to make these heat-exchange systems work. For either, there’s a heat exchanger outside the car hooked to a heat exchanger inside the car to pump warmth or cold into the cabin depending on if you’re blasting the heat or the air-con. An electric fan blows air across these elements, and from there, things get a little complicated.

Obviously, you don’t want full heat or full cold out of every vent all the time, which is where a series of blend doors deep inside the dashboard come in. These flaps regulate the hot/cold air mixture and guide air through specific ducts so you can defog your windscreen, blow cold air on your face, or warm your feet. Obviously, these doors need some sort of sealing so air doesn’t just go around them, so some automakers have used open-cell foam. It’s light and effective, but it can also degrade over time. See where this is going, yeah? Eventually, some cars will live long enough to see their HVAC foam break down. Once it starts to crumble, the stream of air from the blower motor sends it out the vents and into your face. Annoying and mildly hazardous at first, but let it go on, and you could lose effective heating and air conditioning. That’s a big problem.

Perhaps the most notorious cars for unexpected blend door foam parties are 1999 to 2005 Volkswagen Golfs and Jettas, although other Volkswagen models of the ’90s and early 2000s are similarly affected. This Reddit post does an absolutely perfect job of showing the chunks of foam that’ll be flying at a driver’s face as this problem happens, and let me tell you, you don’t want a bit of foam in your eye at 70 MPH. Is it exceptionally subpar foam? Perhaps, although some of the notoriety likely comes from Volkswagen selling a ton of these things.

Unsurprisingly, Porsches of the same era are similarly affected, with visibility of this problem getting a boost for several reasons. Firstly, Porsche sports cars are generally occasion cars, only used in nice weather. As such, they don’t deteriorate quite like mass-market economy cars, meaning they’re likely to grow old enough that this is a real problem. Secondly, Porsche owners have a social community, so you’re likely to hear about this problem online because Porsche owners are online.

While turn-of-the-millennium Volkswagens and Porsches are the most notorious offenders, they certainly aren’t the only cars that can suffer from degrading blend door foam. Here’s a post from the ToyotaNation forum in which one Camry owner experiencing foam disintegration asks “what are my options, really?” It’s a good question, so let’s run through a few potential paths forward.

Option 1: Remove The Entire Dashboard

If you want to go by-the-book, getting to those blend doors will require a whole lot of disassembly. See, their housing sits behind the dashboard, which means the official procedure for models like the 996 Porsche 911 and Mk4 Volkswagen Jetta involves removing the entire dashboard, then anything else in the way of the evaporator case. Removing the evaporator case also generally involves evacuating the air conditioning refrigerant, something you can’t really do safely at home. Want to farm the whole process out to a shop? Be prepared to bust out a comma. Removing an entire dashboard and the heater box behind it is an incredibly laborious process, and once you add the cost of air conditioning refrigerant and blend door rehabilitation, you’re likely looking at a four-figure bill. However, let’s say you drive a super-basic Mk4 Volkswagen without air conditioning. If you want to do this job at home, HumbleMechanic has an awesome video guide to doing it the right way.

Option 2: Oscillating Tool Hackage

Unsurprisingly, some people don’t want to remove their entire dashboard, and depending on the car, will take just about the easiest route forward no matter what the aesthetic results might be. On fried egg-era Porsches, it’s not uncommon for owners to pull the center air vents out and attack the ducting with an oscillating tool to gain access to some of the blend doors and seal them up with aluminum tape. However, this doesn’t give access to all blend doors, and the resulting patch-up of the HVAC ducting with aluminum tape is a bit unsightly. Sure, it might remedy a few symptoms and not take much time, but it’s the sort of thing that would make my eye twitch if I saw it on a nice car. Still, if you bought a high-mileage Boxster with a questionable title for like $3,500, this route might be for you.

Option 3: Getting Surgical With It

As far as these alternative good-enough blend door fixes go, there’s one that stands head and shoulders above the rest, and that’s by going in through existing holes. On a Mk4 Golf or Jetta, that would be through the access panel behind the dashboard. On the 986 Boxster and 996 911, that would be through the cowl. Pull the wiper arms and cowl plastics, and the heater core is effectively right there. Remove a few fasteners, plug a few lines, lift out the heater core, and the blend door housing is right there. Unfortunately, it’s not easy to reach each blend door, but it can be done with an inspection camera and a long piece of stiff wire. YouTuber John Salt recently posted a phenomenal video detailing this method, along with an inexpensive STL file for 3D printing blend door plugs. Remember, don’t use PLA for this, it could melt. This is probably the route I’ll go when it’s time to do the blend door foam on my 1999 Boxster, or I’ll just pay a specialist to do a dash-out job because I’m saving a boatload of money by doing my own suspension refresh.

Obviously, living with disintegrating blend door foam is aggravating, and that’s before we get into the financial side of things. Adding insult to injury, many commonly affected cars aren’t worth more than a few thousand dollars. Once you subtract the recoup of selling say, a 2002 Jetta for a slightly nicer Jetta, it might work out cheaper than having the blend doors repaired.

However, there is another way of looking at this problem. Even in the rust belt, many of the more notoriously affected cars are now more than 20 years old. Up here, you won’t find an overwhelming number of early-2000s Honda Civics or Chevrolet Cavaliers still doing daily duty, but you’ll still see Mk4 TDIs smoking about. Sure, they might have holes in their front fenders, but likely due to a combination of general anti-corrosion measures and careful maintenance, they’re still going long after the end of their expected lifespan. They’ve outlasted their vent foam, so what’s one big pinch-me bill to keep them on the road even longer?

Top graphic image: Volkswagen, YouTube/HumbleMechanic