sealing leaky plastic tank?

dontrinko Thu Oct 15, 2015 8:34 am

I have a tank plastic tank that has a back plate that leaks around the seams. I tried super glue but the fuel seems to dissolve it. Any suggestions ? Don

pkrankow Thu Oct 15, 2015 8:45 am

RTV?
Aluminum safe sealant?
Visit your local auto parts store.

Make sure your choice is aluminum safe since you will probably use it for plastic to aluminum or aluminum to aluminum and so little is needed a tube lasts a very long time. Regular RTV silicone is acidic and will erode aluminum, eventually destroying thin parts.

Phil

fredvon4 Thu Oct 15, 2015 9:14 am

ON a Cox Reed tank to Back plate- there is a small raised section on the tank back and on the perimeter mating surface of the tank a very shallow groove...some folks saliva wet a cotton thread to add in the groove, I personally use Permatex Anaerobic gasket maker as it seems fuel proof and doesn't react to the aluminum or plastic and will not set hard and glue the pieces together

http://www.permatex.com/products-2/product-categories/gasketing/anaerobic-gasket-makers-flange-sealants/permatex-anaerobic-gasket-maker-detail

I also us a 2/56 bottoming tap to chase two extra threads into the case after surface facing the back of the case on a flat glass or other flat surface using 600 grit wet dry paper and oil to remove the original raised burrs from the drilling of the 4 holes

Reason...Cox had an exact screw length..Estes and other sources are not true length and some too long... There is plenty of depth remaining in the holes and by adding a deeper hole I don't worry about false tightening and always get a good tank to back plate seal.

The Du Bro Cat No 360 2/56 tap and drill is NOT a bottoming tap...I just grind off the lead in tip and have a bottoming tap that works just fine...much cheaper than the shipping cost of the real bottoming tap from McMaster or Grainger etc

The 4 tank to case screws get a twist of cotton from a Q-Tip, about a 0.5 inch long, turned clockwise near the head of the screw...not very much just enough to foul the threads in the tank back plate hole

dontrinko Thu Oct 15, 2015 9:46 am

Thanks; This actualy the back plate to a Testors 049. I have some permatex on order that is resistand to oil , gas and several other solvents. Don

fredvon4 Thu Oct 15, 2015 10:14 am

Not trying to be snarkey ----my comment below is so YOU can get better information

This is the Cox Engine Forum BUT we all have many kinds of model engines so there is a place for Non Cox engines

You asked in the Engine Forum for Cox Engines so I assumed it was a reed valve Cox .049 you needed help with

don't sweat it as most all of us just want to help. When you ask questions please describe whet we are trying to work on so you get relevant answers

dontrinko Thu Oct 15, 2015 11:12 am

I get good answers here so.... my question was generic, my problem is specific. Thanks, Don

gcb Thu Oct 15, 2015 9:28 pm

dontrinko wrote:I get good answers here so.... my question was generic, my problem is specific. Thanks, Don

BTW, One of the solvents used to soften CA glue is nitro methane.

George

dontrinko Fri Oct 16, 2015 7:27 am

Thanks George, CA was my 1st try and the back leaked like a sieve. The only good part was that it was easy to remove. I next tried some gasket cement I have, Still leaks.
I have some Permatex on order that is supposed to be resistant to Gasoline, oil and other common solvents. Don

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sealing leaky plastic tank?

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