I originally wrote this how-to post on sealing a gasket when I discovered black streaks on my RV from the gaskets around the outside light fixtures. Like previously revisited posts, everything in purple is information I added to the article. Enjoy.

Sealing a Gasket on the RV

Many years ago, I heard the term “gasket” in reference to cars. I assumed a gasket was a metal thing for a car’s engine. Thirty years pass between the first time I heard the term and now. In between, my vocabulary, apparently, didn’t improve because, recently, in the Oliver Owners’ Facebook Group when the discussion turned to sealing an RV gasket, truly I had no idea what people were talking about.

Shortly after, I called another Oliver owner on the topic of bugs and the composting toilet (which you can read about here) and our conversation circled around to gaskets. She talked about the black streaks from her outside lights. Then she went on to explain the solution for sealing them. First, of course, she had to explain what gaskets were. (Thanks, Melissa.)

After my phone call with her, I examined my own gaskets. Sure enough, I found the telltale sign, faint black streaks running down the trailer from the black ring around the outside lights.

So, in case you are wondering, a gasket is:

a ring of rubber or other material that seals the junction between two surfaces, generally to prevent leaks.

Here is the step-by-step of how to seal an RV gasket. I’ll be honest, this is not a topic I’ve seen on other RV blogs so I’m unsure if other brands of RVs have gaskets for outside lights or for other components. But all RVs have outside lights so my hope is this post is helpful to more than just fellow Oliver owners.

Captain Tolley’s Creeping Crack Cure

Isn’t that a great name? Mostly it’s known as Captain Tolley’s since it’s the only product of the London-based company. It was developed by, yep, a Captain named Peter “Tolley” Jordan. In his 30+ years on boats, he discovered most leaks were not from big obvious sources but, rather, tiny cracks. This led him to develop a product to seal those tiny cracks.

It comes either in a 2-ounce bottle or an 8-ounce bottle. The 8-ounce bottle is a much better deal but I was pretty sure the job wouldn’t take very much so I purchased the 2-ounce bottle.

Two years later and I still have the first bottle I purchased (though it does get gunky at the spout).

Bottle of Captain Trolley's for sealing a gasket and the packaging.
Captain Tolley’s Creeping Crack Cure. Try to say that three time fast.

I’m going to share the text from the package because, even if you don’t have gaskets, you’ll see it is handy for tons more things than just gaskets. It says, “Compatible with: wood, rubber, glass, hard plastics, metals, fiberglass, ceramics, existing sealant, stone, brickwork, concrete.”

It’s described as “A unique penetrating water-based sealant. Formulated to be so thin that by using capillary action it gets into fine cracks. Sets to form a clear flexible and strong seal.”

Instructions from Package

  1. Cracks must be less than 0.8 mm wide, dry and grease-free.
  2. Apply sparingly at 30-minute intervals until filled.
  3. Rapid absorption indicates large leak, so check for drips.
  4. Wipe off any excess immediately with a damp cloth.
  5. Allow 2-3 days for curing. Repeat if necessary.
  6. Do not use below 50 degrees F.

This wasn’t part of the package instructions, but after speaking to a service person at Oliver, it was recommended that I add another coat or two every six months to keep a good strong seal and to protect the rubber gasket.

This is good advice. In the two years since I first sealed the gaskets, I resealed them twice more. And the reason I thought to reseal them was that the black streaks were back. Since the streaks are an indication the gaskets are beginning to break down, it’s much better to seal them before that happens. So now, it’s on the list as a semi-annual chore. This figure might be different for everyone based on the climate, direct sunlight your rig is exposed to and the quality of the gasket. In other words, watch it closely.

I sealed mine during my stay in Long Beach, Washington.

Hack: Sealing a Gasket, a Pictorial

Bowl of water, blue rag, q-tips, Captain Trolley's in package and alcohol wipes.
Supplies. It’s a very inexpensive hack.

Supplies: Bowl of Water, Alcohol Pads, Towel, Q-Tips and Captain Tolley’s

I used Q-Tips because that’s what seemed best for the very narrow gaskets of my project. For your project you might prefer a sponge or a paint brush.

Outside light surrounded by black rubber RV gasket. An alcohol wipe in a person's hand as gasket is being cleaned before sealing a gasket.
The alcohol wipes take a lot of black with them.

Wash the outdoor light, the gasket and the surrounding fiberglass with water and towel. Dry. Follow that with a swipe of the alcohol pad. Not only is it another chance to pick up any debris, but it also will dry out any water to help ensure a good seal.

A white strip of sealant along the rubber gasket of an RV outside light.
It goes on white but dries clear.

Apply Captain Trolley’s

You can see that the product goes on white but it dries clear. It’s quite runny so best to apply in several thin coats rather than trying to do one thick one. Use the wet rag to wipe away any product that doesn’t get on or stay on the gasket.

As it says on the instructions, let each coat try about 30 minutes before applying the next coat. It took me four coats to do the job. You can test it by wiping the gasket after each coat to see if black still comes off on your finger, rag or alcohol wipe.

Outside light on an RV.

Pat yourself on the back for another successful DYI RV hack.

After the initial sealing, the gasket will likely require less coats. In my case, I applied four coats the first time and two coats for each of the subsequent resealing applications.

The real test actually comes after a few rain storms. Be sure to check the gaskets again then to make sure no portion of the gasket was missed. Then on a regular basis thereafter add another coat to keep those ugly black streaks at bay.

Pro Tip: Don’t decide to do the project when you are so close to an active fire that ash falls like snow.

Close up of an outside light on an RV covered in gray and black ash flecks.
The ash was coming down so rapidly, it was a bad idea to reseal the gaskets when I did. No doubt, ash is sealed into the gaskets now.
Close up of an outside light on an RV as well as the top rim of a window covered in gray and black ash flecks.
You won’t believe this but I cleaned all of the ash off, resealed the gasket and this is what it looked like thirty minutes later when I went back around for the second coat.
The fire was so close, the air smelled like a camp fire, the sky was gray, the sun an eerie orange and Quill was covered in ash despite me dusting it off a couple times a day. The fires were part of the crazy fires in the west during the summer of 2020.

Other Easy DYI Posts

To see products recently purchased by readers or to browse and shop at Amazon, follow either of these links. Huge thanks for your support.

Affiliate Link Disclosure. As a result of being an Amazon Affiliate, I earn from qualifying purchases.