Old Car Interior Plastics Can Turn Sticky And Gross. Here’s How I Fixed It In My BMW

Soft-touch interior plastics were supposed to be a good thing. Instead of suffering hard plastic knobs and handles like schmucks, we would be coddled by luxurious, soft touchpoints that felt great in our hands. And yet, for many it has been a curse. As years pass, the soft-touch plastics turn to mush, and sticky mush at that. Interiors ruined, along with your clothes if the plastic goo really gets everywhere.

I suffered this very problem in my otherwise totally perfect E90 BMW 320D. I recently got it back on the road, and the crankshaft pulley has been holding up great. Less great: the (perfectly valid) complaints from the passenger seat. My girlfriend has never liked the Beemer due to the sticky passenger door handle. The door pull is overmolded with soft-touch plastic, and was undoubtedly pleasant to touch when new. By the time I bought the car, the overmold was dissolving into a sticky mess that made using the door a pretty icky proposition. Something had to be done.

The typical solution is to remove the door handle and replace it with a new aftermarket part. That’s all well and good, but it costs $50 and you have to wait for shipping. I only like spending $50 on fun things, like Lego trains and Lego train tracks. Also, you have to take off the door card to get to the bolts, and I fucking hate taking off door cards. Naturally, then, I spent six months ignoring this problem until fellow journalist Kyle Hyatt mentioned to me that he knew a much cheaper way to fix this. Within the hour I was in the car furiously working away with the energy of the possessed. Stick around for the satisfying removal of goop.

The Problem: Thermoplastic Elastomers

This problem all comes down to thermoplastic elastomers, or TPEs. Soft, rubbery-feeling, and easy to manufacture with, a layer of TPE can be applied over a hard plastic part to create a more premium-feeling experience for the end user. The problem is that TPEs are not very hardy out in the real world. UV exposure, heat, and oils can all degrade TPEs until they turn into a gloppy, sticky goop, and there’s no going back. They’re a widely-reviled part of many automotive interiors today, as they feel great in a new car but eventually turn horrible as the vehicle ages.

Basically, automakers took a material that eventually melts when subjected to heat and the oils produced by human skin, put that material all over the car-interior bits that you actually touch and are routinely heated by the sun. Bravo, gang, bravo.

The Solution: Isopropyl Alcohol

The E90 BMW is particularly well-known for suffering this problem on the interior door pulls. On my car, it’s primarily the front passenger door that has suffered this plague, as the driver’s side uses a different design that omits the soft-touch layer. While the typical solution is to replace the part, Kyle explained that there was a way to clean the offending material instead. This involved using a prodigious dose of isopropyl alcohol.

wait tell me more
does that leave bare plastic underneath?
i'd rather do that than pull the whole door card off.

— Lewin S. Day (@rainbowdefault) February 21, 2024

Basically, the isopropyl alcohol acts as a solvent and very rapidly breaks down the TPE. This allows it to be removed more easily and takes away any remaining sticky residue. I had a bottle of “99% strength” isopropyl sitting on my desk, so I figured I might as well give it a shot. “This will be great!” I exclaimed to nobody in particular. I had dreams of spraying on a light spritz of isopropyl and wiping off the TPE in short order, leaving a nice new door handle.

Such folly.

Okay, we're getting somewhere… pic.twitter.com/5xjlQHc13u

— Lewin S. Day (@rainbowdefault) February 23, 2024

Kyle wasn’t wrong; isopropyl alcohol does ease removal. However, it doesn’t dissolve it into a liquid you can just wipe off. Instead, it just kind of softens it a bit. “Mechanical removal,” as is the industry term, is still required. For me, that meant digging away with a screwdriver, peeling off strip after strip of this horrible black gunk.

The area where the soft-touch had already turned goopy wasn’t so bad. I was able to wipe away with some isopropyl alcohol on paper towels and I got down to the hard plastic handle underneath without too much trouble. The bigger problem was the upper, lower, and back sections of the handle. These areas hadn’t degraded much, and still had a largely-intact soft touch coating on them. It was kind of an all or nothing situation, though. If I wanted to remove the sticky part, I had to remove all of it.

leaving it to soak helps a bit pic.twitter.com/44tWBw9GNi

— Lewin S. Day (@rainbowdefault) February 23, 2024

I repeatedly doused the “good” parts of the handle in isopropyl until it too started to free up, then began painstakingly removing it chunk by chunk. Once I got most of the large parts off the front, I grabbed an old scrap of aluminum shower rail and used it like a scraper to remove large pieces from the back. Once the bulk of it was gone, I repeatedly wiped down the whole handle with a paper towel heavily soaked in isopropyl to remove as much sticky residue as possible.

This took about an hour in total, just to do one door handle. At the end, I was left with an okay-looking hard plastic door handle with some scuff marks from my judicious screwdriver use. A plastic scraper might have been a better idea but, you know, whatever. The final look is a bit glossy but mostly looks like it’s meant to be there.

The final result has some scuff marks from the screwdriver and the isopropyl alcohol left a light haze. Note the divot in the handle—that’s intentional from BMW, to help the soft-touch overmolding grab on to the hard plastic part. Ultimately, it’s an improvement, though not as good as a brand-new replacement part, and it probably would have taken a similar amount of time to swap in a new door pull.

If I went through this again, I’d probably just spend the $50 and yank the door card and get it over with. But for parts that are harder to replace, isopropyl alcohol can be a very useful tool.

In any case, I can now invite my girlfriend and other potential passengers into my car without fear that they’ll complain about the gross sticky door handle. That’s a win. Oh, and my crankshaft pulley bolts are still fine. Thanks for asking!

Image credits: Lewin Day