What if your car does not have a radiator cap? Can you still put the pressure tester on the overflow jug to check it that way? - Quora
![Amazon.com: Steelman No. 4 Sized Steel Radiator Test Adapter Cap Replacement for Steelman Cooling System Test and Purge Kit : Automotive Amazon.com: Steelman No. 4 Sized Steel Radiator Test Adapter Cap Replacement for Steelman Cooling System Test and Purge Kit : Automotive](https://m.media-amazon.com/images/I/71G6lTniKZL._AC_UF894,1000_QL80_.jpg)
Amazon.com: Steelman No. 4 Sized Steel Radiator Test Adapter Cap Replacement for Steelman Cooling System Test and Purge Kit : Automotive
![Went to go top off my coolant, cars cold but the cap is real tough. Just wanna make sure I don't need to relieve pressure in case the top pops off : Went to go top off my coolant, cars cold but the cap is real tough. Just wanna make sure I don't need to relieve pressure in case the top pops off :](https://i.redd.it/k9nz2ttfa4y81.jpg)