Gas tank outlet gaskets and how to make them

[raygreenwood]

OK, next mini-project. I finished this two months ago but it’s been busy.
Ok….the real date….started to post this too many times…..
I mostly finished this at the end of January and it’s been this long. My apologies for stalling on all my projects. While it seems like I post a lot…it’s all from my phone either standing around at clients waiting on process…or sitting in parking lots waiting for other things. February, March and April…on the road 1-3 days a week and back almost every day. 1500 miles per week driving…because I am taking care of my parents and one has been in the hospital and into physical rehab…..and got out last Monday! Woo-hoo! No complaints at all….take care of your family!

OK!....gas tank inlet/outlet gaskets!

If you have ever tried to buy a new gas tank inlet/outlet tube gasket….you can’t.
Yes, you will need one when you have to clean out the gas tank and/or when that damn sock filter finally clogs up. The first and only one I found and was able to buy was in the early 90’s at a dealer.
It was a coated gasket paper very similar to the red coated paper O-rings that come on “banjo” style fuel pressure fittings for CIS injection and fuel filters.

One would think that you do not need a new gasket more than once in a lifetime…..but…with the high miles I drove and the filthy fuel we were getting ….as I noted in my “fuel strainer” how too….three times I got pulled over to have to pull out the sock filter and clean it. This gasket always leaked after re-install.

So…rule #1…get the damn strainer out of the tank! Rule # 2…put in a new gasket and keep a spare.


The part # is: 411 201 203

Ok…the parts list description says “rubber seal”.

A few original ones that I have seen from the factory on cars in the junkyard…were indeed a hard, flat, black rubber ring. They had to be Viton or similar…and very thin…roughly 1/32” maximum and they have to be pretty hard for rubber…like 70 durometers or higher (for reference a tire is about 50-55 duro)
If they are not that hard…they squish out from tightening the locking nut as they age…and you leak.

I know this…because I tried a WIDE range of rubber types (that I could find thin enough) when I needed to replace mine the first time. They all squished out and leaked. I finally had to order one from the dealer, took ages to get in and I could ever order one again….because they were listed “NLA”.

The new part I bought…was as I first described. It was a hard, tightly packed, fuel proof gasket paper with a rolled or printed (may have even been sprayed on) outer dressing on both sides. It was probably polyester or urethane looking back on it. It worked very well.
It was just like those banjo fitting gaskets you find in CIS fuel systems.

Later on, I had to make my own gaskets.

So, the gist is this:

If you try to make these out of rubber sheet….they will squish under pressure. With time and age, they keep compressing. You will see fuel seepage.
You will tighten the nut. It will stop seeping. A few months later…some hot and cold cycles and driving vibration….it seep or drips again. You tighten the nut again and it stops dripping…again.

Typically, you get about 3-4 cycles of this and then the little raised ring sealing bead on the gas tank mouth cuts or grinds through the rubber gasket …and you get a real leak.

The general process:

NOTE: I should say up front that this “how to” is as much or more about how to make coated gaskets as it is about making the actual gasket for the gas tank outlet.

1. You need to find a thin gasket paper. A 1/32” is a maximum. A 1/64”. It needs to be listed as fuel resistant. This can be a little harder than you think. It needs to be a fairly hard and smooth surface. Not too “fuzzy”

NOTE: I made this group of gaskets twice. The first time using a gasket paper that I bought just for this about 15 years ago. I used the same paper back then with Permatex Indian Head Gasket Dressing and it worked well.

But….2nd time around….this gasket paper had changed spec. It was too rough and had too much “tooth” so Indian head was miserable. It had to go on too thick (6 coating passes) and therefore was too prone to cracking….so I had to start over and look for new materials/

Here are the first sheets using the old gasket paper and Indian Head Shellac. Note how thick they look. And…not all of the little pinpricks in them. That is from the surface texture. This gasket paper is poor for this use.
Here is a view of both sides of this gasket paper

Note that the left side has a mechanical screen pattern and the right is smooth. This is because paper is ground in a special mill with water or solvent and the batter or mulch that is made is spread on a screen to dry in a kiln.

2. You can use a range of sealers to coat on top of the gasket paper as long as they are fuel proof or fuel resistant.

NOTE: if it seals properly…the fuel will not get to the part where the gasket is “pinched” tight to seal. And…if the gasket paper is really fuel resistant….the fuel will not travel laterally through the paper. Most of these types of papers are made with an adhesive or rubberized binder filled with cellulose, silica or beached vegetable fiber and cast into a sheet under pressure.

3. You need to flatten the sheets. Most of these gasket papers come in a roll and are all screwed up. I first cut them into strips of the right size to work with (more on this in a minute) and then dip them in hot water for a few minutes. Then lay them flat on a sheet of glass, squeegee them dry and cover with another piece of glass or non-rusting metal or aluminum. Generally,…a weight.

Let them dry for a half day, lift the weight or glass, air them for a few minutes or blow dry them for a minute then flip them and put the glass or weight back on top. The object is to let out trapped moisture. Do this about three times over a day and a half. They should be nice and flat like you ironed them

Do not use too much heat…at this point in time….or they may try to curl as the binder shrinks.

Here I have three strips that are laid out to dry on a glass sheet. I am squeegeeing some excess water off with a plastic squeegee.

NOTE: the gasket sheet size. Since you will be coating these with a plastic vinyl squeegee, you want the width of the sheets to be less than the width of the coater squeegee.

4. Tape them down on the glass with the tape lapped over the edge about 1/8” on all sides. Use scotch tape. Yes, it’s a bit grippy…but it is very thin and has a uniform thickness.

It is important to have the tape on each side of the strip of gasket paper. They act like rails for the coating squeegee to ride on so there is a very small, uniform thickness gap between the coating squeegee and the paper surface so that you leave a layer.

5. You will be using a vinyl or tape application squeegee like this:

You can usually find them in any paint store or in the bodywork section of the auto parts store. Buy a new one for this. Don’t use a crusty old one or the nicks in the edge ill leave streaks.

6. Squeeze out a mall puddle of sealer, mostly in the middle.

7. Keep the squeegee at about a 70° angle and uniform pressure and make a single pass to the other end. Lift the squeegee, grab the puddle of sealer with the edge and flip the angle to 70° in the other direction to make a second pass.

Yes…this is the old gasket material and it is not taped. Just an example of the squeegee angle.

This first coating will be thin and ugly with paper showing through. The object of this first coat is to fill and seal the surface. Do not use heat to dry it ….YET.

Let this air dry for a minimum 4-6 hours.

8. Peel up the tape, flip the sheets over. Tape them down and repeat on the second side.

9. With the first layer down on the second side, put a second coat on just like the first. It should be nice, solid coating and should cover fairly evenly. Dry, flip and repeat

10. At this point, with two layers down….you should have a nice semi-gloss surface probably about .002” to .003” thick…..depending what sealant you used (more on this later).

11. Then we draw on the circle pattern with a compass. I first used a compass and caliper to figure out what I needed. More on that later in this document. Here is the sizing of the gasket and the cut lines

12. Then we use a compass cutter like this to cut them out. This is a VERY nice tool. Its still a little flexible. Years ago, this was made of metal but now is made of plastic but still has excellent blades and accuracy.

Here I am cutting test ID circles on cheap cardstock to get the compass cutter set up to the exact size I needed. Work on a self-healing, vinyl cutting pad. You will thank yourself.

The cutting:

First tape them down to the cutting mat. This is important so that they do not move after you cut out the center so you can use the same center pin hole for the compass to cut the OD.

Draw centerlines. You will need them

Yes…that screw…I added to try and make a kind of micrometer setting. Don’t bother. Does not work well and not needed. Just cut circles in cardstock and adjust and cut again until you get it right.

A few done and some with the notches cut in them

A finished part…almost.

13. Once we have the basic “rings” cut out, then we mark the notches for the fins on the inside and trim them cut with a sharp #11 Exacto blade.

14. Then….hang them up and take a small paint brush and some sealer and paint all the cut edges to seal them. I used cheap clothes pins and turn them around after each side dries.

Here is how they fit on the inlet tube

Here is the gas tank opening and also with the finished gasket in it. Notice that there is a raised ring (red arrow) This pinched the gasket against the inlet flange…so this is the actual sealing area. The yellow line notes that the notches are actually slightly off center from the center line. As you sketch these out…measure carefully.

I made the gasket OD slightly oversized from the inlet tube flange…so the gaskets would center themselves in the tank opening.

OK…..the really nice paper I found you can get at NAPA. Its Fel-Pro Karropak and is 1/32” thick and listed as fuel proof. It’s a big sheet so it’s actually cheap for what it is.

The sealant I chose is Permatex Moto-seal. It’s a fast-drying solvent based elastomer that is high temp, slightly tacky when cured and very fuel and oil proof. You can get this at NAPA and other FLAPS. Its very similar to Yamabond and Hondabond. Any of these will work as long as they are thin, pliable and fuel proof.

I have 9 of these gaskets. I will be making another batch of about 10-15 soon. If anyone needs one, they are cheap enough that I will just drop one in an envelope and send to you.
Ray

[Pepperbilly]

Ray,
Wonderful presentation as usual. I actually reused mine…it was still flexible and fit perfectly again. Have not tested it yet so it may or may not hold. I’ll take you up on your offer because I may need one. I can PM my address to you again or you may still have it.

Bill

[raygreenwood]

[jlrftype7]

Sigh, the lengths we go to , to keep old jewels on the road safely....
Very nice write up Ray , as usual.
VW should be paying you for all this historic work since they probably threw out all those important details years ago during the usual paper tossing that goes on once a decade or so at Car Companies.
_________________
'68 Westy- my first VW and vehicle/Bus- long gone.- sold it to a traveling Swiss couple....
'67 Type 3 Fastback, my 2nd car- gone
'69 Semi-Auto Stick Shift Beetle-gone
2017 MINI Coopers, our current DDs
‘84 Tin Top - Hilga....Auto

[raygreenwood]

[big bus mike]