for the cost of a tenner and a couple of hours of your time it'd be worth doing them as it sounds like they could be on there way out. if you leave them then they'll only get worse and will do it on start up hot or cold but do no permenent damage. they don't really cause a problem with you crank case pressure though but something that does connect the 2 is rings but only a slim chance it's them unless you've got space ship miles