imp
Explorer Addict
- Joined
- November 12, 2009
- Messages
- 4,798
- Reaction score
- 779
- Year, Model & Trim Level
- 59 Ranchero F250 D'Line
@Skip Towne @CDW6212RWill do
Be aware the cap has two sealing surfaces. The spring-loaded one seals to 16 psi (or whatever rating cap is), the large rubber ring on the very underside of the cap must seal on TOP of the radiator neck, in order to seal the vacuum created as the coolant in the shut off engine shrinks as it cools, that vacuum pulls the coolant that left the radiator as it expanded, back into the cooling system out of the overflow bottle.
Any nicks or imperfections on the top of the radiator neck can cause loss of that vacuum, resulting in outside AIR being drawn back into the engine. Found often on these new-fangled plastic tanks: the filler neck can develop tiny cracks, hard to see. imp