I just noticed yesterday that the local hardware store is now selling "GORELLIATape" . I''d sand the area good and than try some of this, which is advertised as "SUPER STICK TAPE". If that fails, then empty the tank and have Jack VERY gently smooth over the leak with a very broad tipped sodder gun. This should melt the plastic and seal the hole.
Thanks for the ideas. We don't know the composition of the tank. Guess we will call Blue Bird to find out.
The leak is in such an odd place. I am going to upload some photos to show the leak's location more clearly. BTW, the tank capacity is 100 gallons.
First, is the tank all black polyethylene or is it stainless steel, painted black? --Can't tell from the photo. If it's the black PE, you only have one real alternative and that is to look up a plastic tank fabricator in the phone book and get them to hot air weld the tank. In my prior life, this was the only way we found to repair cracks in PE that had any chance of holding, especially if there was any tank flex involved--and you have plenty of that, sloshing down the road.
What ever you do make sure to get ALL and I mean ALL the RTV cleaned off before starting. It has silicone in it and this will prevent anything else from bonding in that area. Thoroughly scraping, wire brushing and then thoroughly sanding might do the trick. I'd even try to hit the area with a mini-sand blaster.
After cleaning, the JM Weld might do the trick if it's a stainless steel tank.