Do the hir 9011/9012 bulbs run hotter? I have them in my 02 and the housing where the tip of the bulb sits has changed colors. I dont know if this has been this way prior to the original bulbs as it was never a concern.
By design - HIR bulbs run hotter than standard halogen bulbs. HIR use a spherical bulb shape and special internal coating to focus some of that energy back toward the filament. By reflecting that energy back toward the filament, they can heat it up to a higher temperature than normally possible - emulating the light you typically get from a thinner filament.
That's why bulbs, like Silverstars and others, burn out so quickly. Thinner filament, burns brighter and hotter - releasing more photons. Halogen gas is used to limit impurities that will cause the filament to prematurely burn out - but eventually it will break.
Some claim it can run cooler - buy feeling the housing temperature - though that is not 100% conclusive. You can almost always tell by looking at the shielding (metal cutoff part) that sits directly infront of the bulb - that tends to turn a rainbow of colors over time. Even some regular halogens can discolor the shield - depends on shape and depth of the bulb.
No worries - it is perfectly normal. I'd only start getting concerned if the HIR bulb blows up. Halogens just die - my experience with HIR, is they tend to blow up and pepper the inside of your lamp assembly, making quite the mess.
Probably part of the reason they were quickly replaced in older OEM apps (ex Lincolns, larger domestics). But are starting to make a comeback after some new designs were put out there. No more special sputtered coatings, multi-axis focusing, lower temperatures, better bulb/filament physical support, extended lifespans, etc. Looking like they will quickly become the new standard "halogen" bulbs - to compete with current HID and LED options out there.
