DIY - $20 Trunk Seals + Graphic Analysis!

Hi team. Here's a DIY thread in two parts -- something for everyone! Today we'll save $330 by finding a sweet non-original trunk seal for our cars and put that money toward some nice carpet or something!

Part 1: Replacing your long gone, damaged, or deteriorated trunk seal by finding an Lincoln LS at the (North American) Pick-N-Pull.

This is a Lincoln LS. Cool cars if you're into them; I feel like Ford really tried to make them worthy of attention, at least based on how many individual strips of rubber were attached. The rubber seals all over this model make it useful to us. I've never ridden in one but I suppose they're pretty quiet. You'll need to find a POST-FACELIFT (2003-2006) model for this to work; the particular seal off the 2000-2002 cars is to thick.

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Here's the location of the part -- it's the roof seal that runs from the A-Pillar to the C-Pillar. You'll need the seal from BOTH SIDES to have enough length for an E9 trunk. I've already plucked it from the car at the point that I took this picture.

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Get them before they're gone; Ford doesn't seem in the mood to keep producing rubber seals for its cars from this era. You won't find this part new, in other words. However, FYI, the Lincoln part numbers for each side are 1W4Z-5451823-AA and 1W4Z-5451822-AA.

Here's another donor candidate: It's a Jaguar S-Type. It shares Ford's DEW98 platform with the LS and the Thunderbird from the same time.

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The wrecking yard I got these from asked for $10 per strip. Bargain! Here it is attached to my coupe:

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You'll need to cut the custom-molded parts off each end but then you should have two nearly identical strips to apply to your car. The profile of the rubber does change slightly in the middle of each strip and I chose to have the thicker part be at the back edge of the trunk and the thinner part be along the back window. And the result? So far the trunk requires a firm slam to close but gaps all seem correct. I closed a piece of paper between the lid and the seal and felt friction as I slid the paper back and forth.

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Now, this would not be very interesting except that this turned out to have one amazing superpower -- no glue is required, unlike with the original part. It pushes onto the sheetmetal edge that sticks up at the perimeter of the trunk opening, the edge that serves as the backing for the original seal. I've actually applied and removed this strip a number of times as I was experimenting and I'm really excited about how I can take it off and change it around without it taking any paint with it. Except for originality I think I'd recommend this part or something like it over the original strip just because you can take it off, clean out dirt, and look for rust any time you want to. But is it quite as good as the original? I did a little analysis which I'll post as Part 2 below.
 

Blinkling

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Part 2: How to go to significant effort to validate your $20 expenditure (plus the $80 you spent on the other seals that didn't quite work out) and also provide a method for selecting seals for vintage cars in the future:

Here I am with my contour gauge beginning to analyze the actual profile of the E9 fenders and trunk lid:

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After each profile I collected I plunked this contour gauge onto my flatbed scanner:

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...and opened the image in my favorite CAD program. I traced the profiles and generated the following sections which I used to analyze a number of rubber seal profiles.

Original BMW seal along the back of the car (above the tail lights):

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Same original BMW part, but now the section is along the left fender:

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During this exercise it became pretty clear that the original shape was ideal for the application. The main advantages to finding a different rubber seal product would be to 1) save money, 2) have a plan if the BMW part became no-loner-available in the future, and mostly, 3) find a superior product which requires no glue for application and hence won't tend to trap water in this rust-prone area. Below are the Lincoln part from Part 1 and a bunch of profiles from the Steele Rubber online catalog (Steele Rubber Catalog). Some look to me like they'll work and some do not! If you know of any products that might work, please post about the and I'll draw them and try them out in the digital realm.

Lincoln LS roof rail trim as shown above:
Pros and Cons: See Part 1 of this post.

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Steele Rubber Part 60-0078-99
Pros: Similar shape and material to original part;
Cons: Would require glue.
Advantage?: Cost and availability.

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Steele Rubber Part 70-3385-99
Pros: Press-on fit, no glue needed;
Cons: Shape isn't ideal.
Advantage?: Cost and availability, no glue.

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Steele Rubber Part 40-0513-85
Pros: Pretty close fit, soft, spongey rubber;
Cons: Requires glue.
Advantage?: Cost and availability, no glue, more compliant (but less durable) material.

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Steele Rubber Part 70-3590-99
Pros: No glue needed;
Cons: Oh yikes, might be too much squishing required!
Advantage?: Cost and availability, no glue, guaranteed no gaps in sealing :0 .

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Steele Rubber Part 70-3586-99
Pros: Would be perfect if it were 30% bigger;
Cons: Probably won't work but darn if it didn't look perfect. Also, it's not sold by the foot.
Advantage?: Probably none but a sample would be a nice thing to have.

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Steele Rubber Part 60-0732-99
Pros: Looks like a good shape, made out of spongey rubber.
Cons: Durability, needs glue.
Advantage?: Cost, availability.

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Steele Rubber Part 82-0030-99
Pros: Soft, spongey rubber, snug, squishy fit;
Cons: Needs glue; might be prone to coming unstuck due it its high profile; durability.
Advantage?: Cost, availability.

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Conclusion: Stick with the BMW part for originality and certainty in fit; experiment with one of these alternatives if cost or removability are a priority.

As for me, I'm sticking with the Lincoln or Jaguar bit for the time being! Thanks for looking!
 

Marc-M

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One thing to keep in mind is that new or different seals will put pressure on the aperture that closes on to the new seal, and in some cases, you will not get the door/ trunk lid to sit flat due to the pressure placed on it…
 

Cornishman

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Blinkling , great work
If you could find something that actually worked on the two engine bulkheads and still allowed the hood to close that would be fantastic. New or donor, and affordable would be even better.
 

Blinkling

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And good of you to note the Jaguar S type as the Lincoln is even more scarce as e9's in Europe....
A Corolla would have been better but alas. And Volkswagen rubber parts appear to be glued on, at least sometimes!

The 2002 trunk seal worked but closed much harder than the correct seal.
The trunk seal for a E60 5-series wagon (I think?) was heart-breakingly close. It was pretty much the perfect circumference but it took a ton of effort to close.

One thing to keep in mind is that new or different seals will put pressure on the aperture that closes on to the new seal, and in some cases, you will not get the door/ trunk lid to sit flat due to the pressure placed on it…
This seems extremely true for the hood....

Blinkling , great work
If you could find something that actually worked on the two engine bulkheads and still allowed the hood to close that would be fantastic. New or donor, and affordable would be even better.

I think this is the RealOEM section that applies:

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I'm not a fan of this diagram.

We're talking about parts 17 and 18 that run parallel to the firewall, right? 18 is by the hood latches and 17 is right below the wipers, at the trailing edge of the hood, yes?

Here are the numbers:
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I guess you can see which ones I've clicked on...

My understanding is that 17 is the one that everyone is having trouble with.

18 is this guy, 51711810531:

Pardon my rust.
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That's one of the few seals that came installed on my car and it's perfect, judging by the shiny mark it leaves across the underside of my hood:

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There's also the one in the front that seals against the hood right above the radiator:

Pardon the paint overspray from the 80s.
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Is it part 11? It also is a good fit in my car. What are everyone else's experiences?

Allow me a day or two to get out the contour gauge again and we can see about the perimeter of the hood....
 

HB Chris

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#11 is the two seals under the large windshield seal in each corner by the A pillar. All part numbers are here.
 

Cornishman

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Seal 18 is the one that I am having trouble with, it keeps my hood too high.
I feel that my WnN replacement from about 6 years ago is too stiff or too large. It seals well, but I can’t get a good hood close gap.
I am happy to experiment with alternatives, and even happier if they cost less than a meal for two..
 
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