Hi everyone, finally got myself another aftermarket backbox for my mk3 like the cobra this seems to leak on my oem midpipe which is fine with different mufflers very strange. Has anyone else found a cobra muffler to leak on the flange and how did they solve it?
Many thanks
Did you fit a gasket?
this is an example. find the one that fits your car
Yes gasket is fitted.
Or even this one below.
A crush gasket is needed.
I had a different one on my last NC and had to change it as I experienced a slight leak, a dribble of condensation from the joint too. The crush gasket cured it, just make sure the flange mating surfaces are clean and tighten up squarely.
Hi there nick thanks for your reply, I read somewhere if you use these on a backbox with a flat flange and no recess it can bend the flange? Also I used a flat gasket and that’s what I used on my muffler before and that worked fine however they are slightly different sizes by a few mm.
I fitted a flat washer/gasket previously when I purchased a Cobalt back box, the type that has the two holes in it to pass over the bolts. That wouldn’t seal properly so I got that crush washer in the link. For some reason it still didn’t seal properly with that fitted.
I bought another washer some months later, the same crush washer but this time I cleaned up the flange and spigot that’s on the end of the mid pipe and offered it up with crush washer. It all seemed to fit squarely so I bolted it all up and no more leaks.
I think what could have happened with the first crush washer was the mid pipe spigot didn’t fit squarely in the Cobalt back box flange not make a gas tight fit and in turn not crushing that washer enough.
I also supported the mid pipe end when tightening up the joint so it mated together better.
Thanks mick,
thats helpful, I may give that a go. my only concern is with the crush washer, could it perhaps bend the flanges, if the back box surface doesn’t have a recess in it whereas the mid pipe does.
This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.
