I have a radiator that has started leaking oil, by its bolt.

I assume that cause can be that metal is a bit rusty around the bolt, as it is easy to remove the paint when scratching and a bit of rust is below.

Facts: from the factory it had a transparent silicon but it is not stopping the leak anymore. The bolt seem very tight

Should i remove the silicon, remove rust and apply a sealant? Untight the bolt, remove rust, apply a sealant and tight the bolt again?

1 Answer 1


Usually a bolt/fitting that should seal from liquid(oil,water) will either have a sealing washer and/or sealing/plumbing tape/paste on the threads.

Would remove the bolt, clean surface and threads, apply tape/paste, and replace the bolt. Might want to turn the radiator so bolt/hole is pointing up.

Check the hole/surface for cracks. Using a sealant(silicone) on the outside to seal usually will cause leaks, not a good practice.

  • 1
    Yeah, some sort of sealant on the outside sounds like the last person applied a band-aid, and the adhesive has finally worn off. Do a proper fix this time.
    – FreeMan
    Mar 15, 2022 at 13:49
  • is there any risk about removing the bolt? i mean that maybe it is not designed to be removed Mar 15, 2022 at 14:36
  • Bolts are usually designed to be removed. The only risk is that it is a drain bolt, so once removed the oil will want to drain out. Why I suggested to turn the radiator up. If bolt is near or at the bottom, then most likely it is a drain bolt/stopper. If near the top, probably a filler bolt.
    – crip659
    Mar 15, 2022 at 15:13

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