Leaking fuel tank access cover

[canuck]

Hi everyone - recently noticed 10 litres of clean diesel fuel in the bilges of my 2017 Bavaria 37C and on investigation found that the 6" screwed access panel on the top of the tank was leaking. I could tighten it
I am a bit surprised that there is an access cover at all in the top of the tank, especially since if I fill the tank to the top of the filler pipe, the cover would be under a pressure of two feet of fuel oil. I obviously need to not fill too full in the future, although this is hard to regulate.
I have a diesel heater installed and I am wondering from other posts if the access cover was added because of this.
Does anyone else have this access cover, and what would be the best way to seal this to avoid a future problem.  Am thinking of cleaning it up and siliconing it in place, but not sure about the effect of diesel on silicone? 
Any help would be appreciated. !!
Nigel

[tiger79]

My 2014 Cruiser 37 only has a round plastic access cover, moulded into the tank, with an O-ring seal.  If your access panel is leaking, perhaps you could replace it with a new one.  Tek Tanks have some - https://www.tek-tanks.com/product-category/tanks/tank-accessories/inspection-hatches

[Yngmar]

I am a bit surprised that there is an access cover at all in the top of the tank

Funny, most who have a tank without a inspection hatch complain about the lack of it (for tank inspection/cleaning).

Am thinking of cleaning it up and siliconing it in place, but not sure about the effect of diesel on silicone?

While you can find diesel resistant sealants on the market, you will be unlikely to find one that sticks to the HDPE the tank is made of, even if de-greased thoroughly, so that idea is not going to work.

So only compression seals (gaskets, o-rings, etc) will work here. Did you inspect if the hatch has an o-ring that maybe just needs replacing, or if the lid is cracked? Worth checking out how it is supposed to seal and find out why it doesn't, before looking into replacing it.

[Lyra]

you will be unlikely to find one that sticks to the HDPE the tank is made of,

I did find something that seems to do the job, which I mentioned here in the past - http://eclecticproducts.com/products/seal-all.html

[Yngmar]

you will be unlikely to find one that sticks to the HDPE the tank is made of,

I did find something that seems to do the job, which I mentioned here in the past - http://eclecticproducts.com/products/seal-all.html

Hmm, quoting from their datasheet:

Not recommended for use on Styrofoam™, polystyrene, polyethylene, polypropylene or polypropylene plastics

[Impavidus]

Canuck.
The issue in my opinion will be based around the O ring that seal the inspection cover, not the tread or anything else. The seals used on all Bavaria  tanks from black water to diesel only have a limited life span. Especially when exposed to chemicals, or a harsh environment. All the O rings are standard sizes but you need to either find the supplier or OEM to replace them as part of your routine maintenance. Most Bavaria's were also not supplied with the special tool to remove and replace the inspection covers so you will also need to make one of these. It's quite simple you just need two bolts and a piece of timber or aluminium bar. Drill two holes  in the timber that correspond with the distance from the finger holes at 108 degrees (opposite each other) fit two bolts through the holes either hex head or socket head. Whichever fits the finger holes best. Use this to either re - tighten or remove for inspection the hatch. I Have just helped a fellow Bavaria owner replace the black water tank and fresh water tank O rings on his 37 C 2005 the Diesel tank is showing signs of the same O ring failure. You may also want to check your deck fillers O rings to water, diesel and black water. these also have a limited lifespan.

Hope this helps.

Ant & Cid SV Impavidus       

[Salty]

Thanks Ant for the tip regarding deck filler “O” ring seals.

[Lyra]

Hmm, quoting from their datasheet:

Hmm... they may have changed their specs (or just want to keep it safe and not promise anything).
I found my correspondence with their technical service from 2012 where they said it was OK for polyethylene (but not suitable for polypropylene) . Anyhow - my fix is still holding.

[Odysseus]

Try to get a silicon "O" ring in preference to nitrile and if pos get some plumbers silicon grease, that does not contain any petroleum product.. you can find them on EBay, in the automotive section,.

Hope this helps

Odysseus
Bav 38

[canuck]

Thanks everyone for your input.  I will need to wait for a bit until I have used up some more fuel so I don't make a mess when I remove the cover.  It seemed easy enough to unscrew with a plumbers wrench, in fact I was able to overtighten it so that it jumped the threads on the cover. Seems strange, so it could be that the seal is mushy and too easily compressed.  Will find a more suitable seal.
Thanks again !