I'm waiting for other parts to get done in my power steering and alternator refresh, so I decided to take today to tackle one of the WYAIT things I'd put on the list with parts off the car. Apologies if this has been addressed already but I thought I'd share.

Here was the state of the sealing foam on the cover of my wheel well liner:


Some material was already missing, apologies for the blurry pictures


Looks OK, so long as you don't touch it (cue Spinal Tap reference)

When I went to clean things out things pretty much just disintegrated, which is why the pictures here are taken near the trash bin. I just dug things out with my finger. What wasn't oil/ATF/I-don't-know soaked came off pretty easily but left behind a good bit of residue and foam material on the walls of the trench. What was soaked also left behind a good bit of residue on the walls of the trench but with a lot more foam material still attached.

I cleaned up the trench with sparing use of brake cleaner (mostly just acetone) and paper towels, learning a couple of things in the process:

1) If there is adhesive that was used for the sealing material, it comes off pretty nicely with acetone
2) The blue shop paper towels absolutely disintegrate when trying to scrub with any kind of force with brake cleaner (I haven't tested with the chlorinated brake cleaners, so I can't comment about that stuff)
3) Regular paper towels are great with brake cleaner and stand up to scrubbing this part way better. It only ended up taking me a couple of those to get to this point:




There are still issues with the cover, but I don't have a plan for this just yet and it's been addressed in the past. Until it really lets go, I'm rolling with this part for now:


Not a part of this DIY but also not looking brilliant

I measured the trench and came up with a couple of solutions. The first is a rectangular profile EPDM foam. This looks the most OEM but I was not able to find something with the correct dimensions without an adhesive backing. The white bits you see peeking out are the adhesive backing, which I did not remove:



You can see the foam and backing on top of the cover



Because I didn't like the idea of the adhesive, and on top of that the adhesive was on the "wrong" side (meaning difficult to get in position if I wanted to use it: I'd want it at the bottom of the trench, not the side, and jamming the foam in with the adhesive on the side seemed tricky at best), I found this other foam with the right diameter to wedge itself into the trench, but it's definitely not OEM looking:


Round profile, closed cell, good contact with trench sides

I ended up going with the square profile material and leaving on the adhesive covering (the white tape stuff that peeks out a bit). I ended up using just over 5 feet of material, which is a bit of a bummer because it is sold in 5 foot lengths. The good news is that I still have the other side of the car to do and PET indicates that more will be required so the 10 feet I bought will let me do everything I need to.

For those that are interested, here's what was on the packaging of the square profile material:



Finally, here are the links for where I bought things:
5/8 inch diameter, I chose orange but also comes in white: https://www.mcmaster.com/1578n26
5/8 x 3/4 inch profile EPDM foam: https://www.mcmaster.com/1566n165

ETA: From Stan's feedback, below, maybe this is a better choice to get things to sit proud (which mine currently does not): https://www.mcmaster.com/1566n166

I didn't inquire with vendors so I don't know what they offer or how it compares on price but I always recommend going there first; they're an integral part of the lifeblood of keeping these amazing cars going and deserve our support. I just wanted to see if I could figure this out on my own and this is what I came up with.

If anyone wants the orange cord, let me know and it's yours for the price of shipping.

Cheers

 

the factory foam is still available in different lengths and reasonably priced,Roger has it
the idea with the foam is that it will sit proud of the channels so to block off air once its in position thus reducing road/ wind noise

 

“I didn't inquire with vendors so I don't know what they offer or how it compares on price but I always recommend going there first;”
You should have followed your own advice. The stock foam is cheap (less than the $50+shipping you spent), readily available, and is a better product. Got mine from Roger.
The stock foam is open cell foam coated with a light cover coat/wrap to keep it from absorbing moisture. There is no adhesive, what you cleaned out was the cover coat.
It friction fits the channel and sticks out about 1/2” or so, if IRR, and is soft enough to conform and somewhat seal the edges.
Filling the channel but not sealing really accomplishes nothing.
Don’t feel bad, we’ve all tried to reinvent the wheel only to find the wheel is cheaper and works better.

 

I used spray expanding/insulating foam, cut if flush when dry, and undercoated over it.

 

Just did this job...the seals and the front covers, which were improperly attached and cracked badly. Like you, I tried to find a good local foam alternative but couldn't find anything in the dimensions needed to properly seal the wings. Just buy the OEM foam, it's like $40 bucks and will last years. So many expensive electrical systems behind the front wheel wells that need protection.

 

Thanks everyone for the feedback. I agree about a lot of the things said but a question:

Part of what I wanted to avoid was an open cell foam, which Billu references above, and which is what it looked like the original foam was. From a sealing perspective, isn't a closed cell foam preferable? I spent a good bit of time trying (and failing) to get the right orientation of the foam, meaning that the casting and cutting orientation would end up with the totally closed face exposed. This was the best I could come up with, though I didn't measure the dimensions well enough, and it's made from a material (EPDM) that is used in more challenging applications (things like the side marker gaskets) which see a lot more impact from the environment. I figured that in a more enclosed space, it would be good for just about forever.

Your thoughts on this are appreciated.

Cheers

 

The stock foam is $6 for 32"

 

@ROG100 : That's a great price

 

I was originally going to used open cell foam used to seal window air conditioners but didn’t because of it soaking up moisture
Original is a coated open cell foam, easily compressible but coated to keep moisture out.
When I saw what it was and how cheap it was, using anything but the real stuff seemed to be foolish.
The fact that the coating was gone after 30 years.....
Not a problem.
I will probably be gone when the new foam needs to be replaced.

 

Actually although it's good that the stock foam is still available - I think it was always a poor materials choice by Porsche for long term usage in that application. I have thus far always replaced with the stock foam - but every time I take the splash shields off (usually >5 years between) it has deteriorated to a mushy, friable mess that falls apart as you touch it - much as you described in your initial post. Since my car has been in Phoenix for >20 years it sees very little rain/moisture yet it seems sodden/oily. Note that yours had already lost all of the actual sealing area - which is that part that sticks out of the channel by ~1/4" all round.

I am now in the process of replacing mine with some left over material I had previously used for under-hood insulation pad. Its 3/4" thick and closed cell vinyl/nitrile foam that is water, heat, oil & chemical resistant. It does need to be cut intro strips for this, But it cuts OK (super sharp knife) and lasts extremely well, I expect this to be much more durable than the stock material. My under hood pad has been on the car since ~2006 and still looks and feels exactly like new. It gets a whole lot of heat cycling and exposure to oil etc fumes with zero impact. I've also had a small piece laying outside for years also with no ill effects It's expensive stuff (aircraft grade) but totally worth it to me, I don't mind paying more to avoid the need to do this over and over again. BTW gluing into that channel is not needed or recommended - a friction fit is stock and quite sufficient. I'm over-sizing mine for a slightly snugger than stock fit.

https://www.wicksaircraft.com/shop/soundproofing-foam/

Alan