I take my car apart quite often and gave up on those things, I found a tywrap poked through the rad with a nylon washer on it works great. O
n the fan side use another tywrap slid over the first one to hold it all together. I use this method to hold my fender covers on AND most of my front bumper
it has not ever given me any problems.
Use good quality tywraps and you will never have any issues IE: T&B TY27MX type military spec, available at any electrical wholsalers ( Eecole)