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81 Avanti Gas Cap and Sunroof Seals


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Hi folks.  

Brand new Avanti owner here.  Just got an 81 yesterday, and have 2 first orders of business:

- no gas cap.  I have heard that there are inexpensive Stant and NAPA ones for later Avanti's, but not sure if they are year or engine specific.  Mine has the regular 305 engine.  Any 81 owners with advice on gas caps?

- i did not intend on getting one with a retractable sun roof, but I did.  and of course it leaks like an indoor waterfall.  Before I start tearing into it, does anyone have advice/source on replacement seals for this?  i've heard that leaks are common.  The motor seems to work fine.

- Oh, and if there is any advice on car covers, I'm in the market for one immediately until some miracle makes room in the garage.

I intend on having many questions as the year goes on!  Hi everybody.

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I don't think there's anything special about the gas cap, your Avanti should have a standard filler for unleaded gas, so any low-profile gas cap meant for unleaded fuel should be OK (it just needs to clear the filler door, and since the gas filler door locks, there's no need for a locking cap).

I formerly owned an '80 Avanti with a sunroof and collected some info about them as I came across it; I emailed that info to you just now.

You may be able to find seals here: https://secure.cougarpartscatalog.com/Mercury_Cougar_Sunroof.html

Car cover: you did not say where you live... weather is a very important factor in car covers; one piece of advice: if you live in a dry sunny area, avoid Budge car covers, I've had several and they don't last anywhere near as long as they claim.

Edited by WayneC
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Here is the gas cap on my 81, RBQ-3318 - click left and right, 2 shots


I, too, have a sunroof but wish I didn't.  I ran across several articles on dealing with them.  Apparently the guides that the glass panel uses when it opens come unglued from the bottom of the fibergass top so there is a method to get them glued back up that does not look too difficut.  Where does your sunroof leak on the inside?  Here is one of the articles


Ed M


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Hi Wayne and Ed.  thanks!

I checked that cougar site, and it seems to be for ASC sunroofs.  Are you saying the weather-stripping is the same for the ASC as for the Skytops?

That Bob Johnson article is the same one I'm looking at!  Mine is clearly separated from the roof, so thats one issue, and it drains into the cabin on the driver side by the door, as if the drain tube is disconnected or broken or?  Not sure how to get to the drain tube itself to check it.

ALSO: related question, per the article above, it seems JB Weld was the go-to adhesive, but this was all a couple of decades ago, so wondering if that is still the case, or if there are any newer better adhesives to consider?  Since this seems to be a common failure.

Wayne, you said you emailed me some material, but it has not arrived. 😞  Javier@Cinefont.com 

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I'm not all that knowledgeable on sunroofs, just collected info in case I needed it. I think the ASC info may have come with the papers I got with the '80 I owned, so I assumed it referenced the sunroof on that car... don't know if they still carry parts for that sunroof model, or even if the company is still in existence, you'll have to research it.

I misspoke about "email" (there's no way I could get your email address) ...check your profile to see if there is a message there for you.

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On 5/27/2021 at 10:38 AM, R2W55 said:

there is an article in the latest issue of the Avanti magazine about sunroof repair

Hey thats great!  But as a noob here, how do I access the magazine?  I paid my membership, which I thought included access to the magazine, but how do I bypass the paywall of the JooMag popup?  It keeps asking me to subscribe and pay for the magazine.  😞


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I don't think your membership includes access to back issues; new issues are mailed to you. So depending on when you paid your membership, you may or may not get the "latest issue". Unfortunately, I was late renewing, so I don't have that issue, either.

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  • 3 weeks later...

I've found most sunroof leaks are caused by clogged sunroof drain tubes causing the "ice cube tray effect" when the watwe backs up into the sunroof channel and spills over/into the inside of the car. Check the drains first for blockage. As a side note, Avanti II sunroofs drain into the hog troughs so there is no way to blow compressed air "backwards" into the drain tube to move the blockage. Using compressed air in the "reverse flow" method is effective, however, it can also blow the drain tube from its fitting causing an bigger drain problem. I've found the blockage is up high near the roof when some leaves got into the drain tube and clogged them. I take a piece of wire smaller then a coat hanger and run it down the drain tume hole located in the sunroof channel. Then pour water into the drain hole. If the drain is clear, you will see water draining from the front section of the  hog troughs. 

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