[C320-list] Tightening don onto rubber gaskets?

[Greg Flanagan]

On my fuel tank sending unit the SS screws melded and stripped the aluminum threads in the tank. I drilled out the tank threaded holes, inserted SS screws from below (inside the tank) and permanently attached a flange (with gasket) to the tank with SS nuts. In the 1/4” plastic-wood flange I had fixed countersunk screws as studs sticking up. This assembly never needs to come off.  I attach the sending unit with gasket to these studs. This way I have only SS connections and can remove and replace the sending unit easily. This facilitates getting into the tank for period maintenance. I hand tighten and then apply slight torque with a small ratchet—maybe 10lb.


Greg Flanagan
Hoop Dancer #1076
Sidney, BC 

> On Dec 18, 2017, at 6:46 AM, Graeme Clark <cg at skyflyer.co.uk> wrote:
> 
> I've installed a new fuel sender unit and added some fuel tank inspection ports. I have used 1mm gasket material for the ports (Viton material) and the sender unit had a 2mm gasket supplied.
> 
> I have also used hylomar non-setting gasket sealant.
> 
> Not having looked too closely at the old gasket when i removed the broken sender, I was surprised to find the extent to which the gasket material compresses and squeezes out to a diameter greater than the plate. I dont want to over tighten the screws (on a test piece when I did a destructive test the screws (stainless) sheared before the threads (aluminium) stripped, to my surprise).
> 
> On the other hand I dont want to leave any possibility for leaks.
> 
> can anyone give guidance on how tight i should be doing up these bolts - (no 10 self tapping flanged hex headed) either in terms of torque or in terms of how much gasket squish!
> 
> Cheers
> 
> Graeme
> ‘Jakar’, 1996, Hull 366.