Longtime Piper pilot discusses how to replace a Piper Cherokee door seal, with 16 pictures to help guide your way.

By Mike Jones

Having a pleasant return flight from Pittsburgh in my Cherokee 180, I glanced over my right shoulder to see an arc of clear blue sky surrounding the upper-right corner of the door. This observation went along with the sudden realization that the far-right carpet piece directly under the door was missing. During the rainy overnight, it had become soaked from a leaky door seal, and in my haste to dry it out before departure, I somehow left it on the ramp! “I guess it’s time for a new door seal,” I thought, “and maybe some carpet!”

Getting Started on a Piper Cherokee Door Seal

While there are several door-seal options available, the seals I chose are offered by Knots2U at Burlington airport (KBUU) in Burlington, Wisconsin (Photo 1). Not only have I had good luck with their products in the past, but I am also just a short flight to Burlington from my home base in Kenosha, Wisconsin.

I discussed the replacement process with the folks at Knots2U face-to-face and learned that it is imperative, after removing the existing door seal, that you check for wear on the door hinges, replace those if necessary, and realign the door to the airframe before attempting to install the new seal. The instructions for doing all this come with the seal. After providing my aircraft serial number, the correct Knots2U part number was located and purchased, along with the Knots2U recommended glue remover and seal adhesive.

Back home, I read through the instructions and carefully followed the procedure to check for wear in the door hinge. You detach the lower door brace by removing one screw (Photo 2). Be sure to capture any washers, the screw and bushing, and put them in a safe place where they will not get lost (Photo 3). You will not need to reinstall them until the job is done.

Gently lift up on the door while it is open part-way. There should be no play in the hinges. If, while you do this, you can see the door wobbling back and forth as I did, you know the hinges are worn and need replacement. Fortunately, Knots2U also has the hinges, washers, and nuts in one kit, and clevis pins, washers, and cotter pins in another! I flew back to KBUU and picked up what was needed — you should check for hinge wear first, so you can order all parts at once.

Click on a photo for a Piper Cherokee door seal popup slideshow.

Removing the Piper Cherokee Door Seal and Hinges

To properly remove the old seal and install the new, the door must be removed from the airframe, even if your hinges are OK. Remove the cotter pin from the bottom of the hinge clevis and, while supporting the door to relieve the stress, tap the clevis out from the bottom (Photo 4). In my case, someone long ago had replaced the clevis pins with AN bolts and nuts! If you have that configuration, simply remove it, and be careful not to mar the paint on the airframe while you do this work. (Ask me how I know.)

To remove the hinges from the airframe, you must loosen the interior trim panel just forward of the door frame, enough to get a tool on the back side of the nut securing each hinge (Photo 5). While keeping the nut from turning, place an adjustable wrench over the external hinge and unscrew it. Do not drop the nut inside the side panel or you may have to remove the entire panel to retrieve it. It really helps to have another set of hands, and I have to thank our own Scott Sherer for coming over to help out and share his experience with replacing hinges on his Arrow.

The new hinge kits will have everything you need, including the hinge itself, nuts, and washers in two thicknesses for vertical adjustment of the door (and also for placing behind the hinge to make the door flush with the airframe surface). It also contains the clevis pins, cotter pins, and instructions. Install the new hinges and, as the instructions point out, you do not have to crank tightly on the nuts to hold the hinges in place, just snug them up. See the old hinges and the new hinges in Photo 6.

Do not replace the interior trim just yet, as you will have to remove and install the door several times to choose the proper washers to align the door to the airframe. But first, you must remove the old seal. Many of us, in an attempt to cure a leaky door, have also added sealing material to the airframe opening itself, but all of that material has to be removed as well (Photo 7).

Click on a photo for a Piper Cherokee door seal popup slideshow.

Removing the Old Seal

Removing the old adhesive is a slow process. Be prepared to work on it for as long as it takes and try not to cut corners or attempt to speed up the process as, in the end, you will only make more work for yourself (Photo 8, Page 32).

Begin by laying the door on a soft blanket at a comfortable working height. Grab the old door seal with a pair of pliers or vise grips and see if you can pull it off in sections. If you must scrape it off, use a plastic tool so as not to scratch the surface of your door. In my case, the seal came off pretty easily because of its age. However, the old adhesive did not! ! (Photo 9, Page 32). Removing the old adhesive so you have a clean surface for the new seal is where most of your effort will now be focused.

Knots2U sells a glue remover that is not inexpensive, but it works very well and without the fumes associated with MEK or lacquer thinner. Amazingly, it did not remove the paint! Of course, it depends on the kind of paint, so a test in an inconspicuous area would be appropriate.

Wearing rubber gloves and eye protection, apply the gel-like remover with a brush along an 8- or 10-inch section and let it sit for 10 minutes (Photo 10). The old glue will soften, and you can rub it off like it was old rubber cement. Of course, there will be stubborn areas which require a second treatment, and some mechanical help using a plastic scraper or brass bristle brush (Photo 11).

Working on these small sections, completely remove all of the old adhesive from around the door. It should be very clean, but there may be some areas that are just stubborn — that is OK, but don’t give up too soon!

Click on a photo for a Piper Cherokee door seal popup slideshow.

Door Alignment

You are now ready to follow the detailed instructions that come with the new Piper Cherokee door seal and align the door to the airframe. To do this, you select different hinge washers provided in the kit until the door, when it is shut, has a uniform gap between it and the airframe, and the surface of the door is both parallel to and even with the surface of the fuselage along the hinge line.

During this process, you may have to remove and install the door several times, while you utter profanities at the washers and tight-fitting parts, etc. Don’t be discouraged! Though it will not be absolutely perfect, because the doors were basically handmade and hand-fitted at the factory, the fit will be very good and likely much better than before the hinge replacement (Photo 12).

Scott’s experience was a great help here, but again, the instructions provided by Knots2U are very specific about how to do this work. One point — if you have stripes painted on your aircraft that cross the door, and if they were painted when the door was out of alignment, they may jog a bit when the door is properly aligned. Fortunately, I lucked out!

With the door properly aligned, snug the hinge bolts and replace the interior trim panel. If you have not had a break, now would be a good time. You are about to install that brand spanking new seal! In fact, maybe you would like to sleep on it and get a fresh start in the morning?

Click on a photo for a popup slideshow.

Installing the New Seal

With a clean surface on which to place the new seal and the proper adhesive on hand, we are ready for the new seal. But wait — not so fast! First remove the door and put it back on the blanket. Do not try to install the seal with the door on the aircraft.

Take time to study the detailed drawings of the seal and its proper orientation as noted in the instructions. The seal profile is roughly an ‘L’ shape, with each arm of the ‘L’ a different shape and thickness. The instructions show that only one arm of the seal is glued to the door. While this works as advertised for the straight sections, because of the door shape at the corners and the tendency of the seal to fold back on itself when placed around those curves, I found it necessary to put some glue on both surfaces around the corners of the door or it would not close properly and the seal would fold over on itself. The instructions also warn not to stretch the seal around the corners, but to simply lay it in place (Photo 13).

Another point, not covered in the instructions, is how to handle the seal at the door latch (Photo 14). The top latch was not a problem, but the main door latch at the side was. The clearance between the striker plate and the door was smaller than the thickness of the seal that lay against it. Because of this, the seal gets pushed back and folded over on itself when you shut the door.

My A&P, who was consulted before, during, and after the project, as he would eventually have to sign off, suggested I trim the seal around and close to the latch while keeping a bit of the inside angle of the ‘L’ shape to help channel water past the latch. Easier said than done! It was easy enough to trim, but with the exposed foam of the seal, it just did not look quite right.

I cut some extra seal material and glued it along the trimmed area to sort of finish off the appearance. When running the seal along the bottom edge of the door, be sure to position the seal so it will clear the threshold when shutting the door.

Start at the bottom of the door. In applying the glue, Knots­2U recommends putting glue on the door first, one 8- to 10-inch section at a time, and letting it dry. Then coat the seal and, while still wet, press it into place. It will bond fast, and I found this method works quite well. Continue around the entire door and when you get to the beginning, cut the seal with a sharp razor blade and glue the ends together. The seal comes with a small packet of silicone grease. Spread this over the seal and wipe off the excess.

This helps keep the seal pliable and is recommended as periodic maintenance. The hard work is done, so take a break and celebrate!

Installing the Door

Time to install the door with all the washers in their proper place. You did write down where they go, right? If all is well, the door will actually shut! It will take a bit of extra force initially, but after sitting overnight, it will shut much easier, as the new seal adjusts to the fit.

Now is the time to make any necessary adjustments to the upper latch or the side latch. The instruction sheets cover both. For the upper latch, after removing the plate, the bar on which the upper door hook grabs can be rotated in or out to adjust the fit. On the side latch, the striker plate can be loosened and moved slightly in or out to adjust the fit. The object is to have the door as flush with the fuselage as possible.

You may wish to make some adjustments to the wind lacing material surrounding the inside of the door, designed to keep any small air leaks at bay. Removing the trim screws section by section, reposition and trim the excess wind lacing material held under the trim piece to move the wind lace in for a snug fit around the door interior. It should snugly cover the gap between the door and the airframe (Photo 15).

When all the adjustments are complete, shut the door, kiss your bird goodnight, and come back a day or more later before opening the door again (Photo 16). The new seal will mold to the airframe, and the door will be much easier to operate from then on. If you wish to paint the new hinge hardware, now would be a good time. I painted mine white.

Finishing the Paperwork

Ask your A&P for a final inspection of all your hard work and for the appropriate logbook signoff. Offer to pay for the guidance and signoff. You saved a bundle, learned a lot, and he or she will likely help you again in the future. You’ve got it sealed, you’ve got it signed, now take delivery and go for a flight. You will enjoy the noise reduction, wind reduction, and dry carpet!

Mike Jones is an instrument-rated commercial pilot for both fixed-wing and helicopter, a remote pilot, and current CFI. He has enjoyed flying his 1966 Cherokee 180 between its 36 annual inspections. He also ran a webinar for Piper Owner Society members — watch “A Taste of Homebuilding Through an Autopilot Install.”