Radiator cap leak cured

ratwing

Active Member
Ever since I got a small dent on the top edge of the rim on the filler, the dished metal washer in the cap no longer seals and water leaks out and drips down the rad onto the ground - I've got an expansion bottle not a tank.
I can't knock the dent out and don't really want to drain/remove the rad to solder on a new filler neck, so whilst thinking what to do I made a cup of coffee and noticed the jar lid had a plastic wad (100gram jar of Carte Noir, others might have similar wads) that looked about the same diameter as the dished metal seal.
I prised it out, measured it and it was about 2mm bigger than the metal seal, after cutting a hole in the middle for the spring it fitted inside the rad cap perfectly.
The wad is a thin foam plastic, I don't know what type, but so far it's stood up to the heat and seals perfectly.
 
I think you've just solved half the worlds motoring problem.
I going to get a coffee and see whats in the grains . Well done . Hope the seal lasts. If it doesn't, at least your on the right track.
 
some rad caps have a rubber layer some don't in my experience. The rubber layered ones always seem to behave better though.
 
The caps with a double seal are designed to work with an expansion tank or recovery bottle. As the top of the neck is sealed when the engine cools a vacuum is created in the radiator this then sucks water back from the recovery bottle as long as the pipe in the bottle goes below the water level in it.
 
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