The Radiator Cap Assembly in my 87 got a substantial crack in it (Not honestly sure how) and I'm looking at replacements, none of the local stores carry them, but mazdatrix does. However, they have an aluminum one and a plastic one. The one in my car is plastic, so i figure aluminum is probably stronger, but it is also 10 bucks cheaper...Why is this? Is this logical choice not the best choice, would i be better off with the more expensive, plastic one? Got a picture with the part numbers for you guys.

 

Then again i just realized the aluminum one doesn't have an overflow tube, which I'd assume i need...I guess that just answered my question. Sorry for wasting the space with this thread, you can lock it or whatever you guys do.

 

only go with the plastic if your radiator does not have the pressure release nipple, otherwise always use aluminum over the plastic as it will outlive the car where the plastic one will eventually fail again.

 

They're semi-pricey. My car came with the plastic one with the overflow tube. It broke and I used a plastic one without an overflow... I ran into the problem of the coolant slowly spewing from the hoses. I bought a used one with the overflow tube for $13 from a forum member. Solved my problem. So, I agree with Karack... Go with what your car requires.