Answer
Aug 04, 2025 - 04:45 PM
Are you referring to a rubber block-off plug or cap used to seal off a coolant line or bypass hose, like when you’ve removed the heater core or blocked off a xxxx on the intake or water pump? If so, the usual method is to use a worm gear hose clamp or spring clamp to keep it secure. The plug should sit fully over the pipe, and the clamp should go behind any flange or bead to keep it from sliding off when pressure builds.
Make sure the surface of the pipe is clean and free of rust, corrosion, or coolant residue. Otherwise, the plug may slowly work loose under heat and vibration. Also, double-check that the plug is rated for the temperature and pressure in that part of the system. If you're dealing with a capped coolant line, pressure can spike when things heat up, and a cheap rubber cap might not hold.
If you meant something else by “dormant plug” — like a freeze plug (core plug), intake vacuum cap, or even a block-off plate — let me know and I can steer you in the right direction.
