Flange sealant question.

[boosted]

my new alloy sump is leaking...from alloy to cast joint.

I used clear 250 degC rtv silcone on alloy to cast bottom of rx8 engine....but after heat cycle its weeping in a few places. I used this several times with standard sump spot on but does not appear to be up to the job with the alloy sump.

Searched for sump sealant here there and everywhere but not sure what i need.....i even went to VW but they want £21 for a long half filled tube that will do half a sump.....( there sumps are alloy and strip there drain plugs threads lol).

any personal recommendations ?

[Alexsavv]

Try and stud your sump onto the engine, would give a tighter hold