if the overflow tank cap on a 89 IROC does not screw down snuggly,goes on ,but does not appear to tighten when turning,can this cause an overheating situation??trying to clean out area to work on car to solve the new overheating problem that has occured recently,the fans are not running when the gauge reads past 220,so going to change thermostat,flush system(even thou recent fluid replenish)and check on sensors,the one that controls the primary fan(ECM control)on passenger side between plugs?thanx for any advice ,help

 

sorry but no. The cap will have nothing to do with your overheating problem.