As the market place should be aware, CPC radiator caps have a unique annular seal that not only seals the surface of the radiator neck but also the inside of the neck to help prevent any splash back when there is pressure in the cooling system and the cap is turned to the safety position.
No other cap in the market has this feature but it has caused some problems when it comes to testing our caps.
When fitting our radiator caps to a tester the first thing to check is the position of the blow off hole in the adaptor.
All adaptors require this hole to allow the cap to release when it reaches pressure. Similar to the overflow tube on a radiator neck releases pressure either into the atmosphere or an overflow bottle.
Some adaptors have this hole in different positions, which is what has caused us some grief in the market place.
Because of the annular seal in the CPC Radiator cap, the step part of the seal goes into the inside of the adaptor and in some models sold in the market place our seal actually covers this hole, that then does not allow the adaptor to release pressure so the cap is then rejected when in fact there is nothing wrong with it.
Please when you next test a CPC radiator cap check this process and make sure you are testing correctly.