This is a complicated question to answer for several reasons. The short answer is: It largely depends on your specific GPU vendor and their terms as to whether they'll give you any grief.
The long answer is: The FTC has deemed warranty void stickers to violate the Magnuson-Moss Warranty Act if enforced incorrectly. What does this mean? Well, simply taking your components apart and performing maintenance on them cannot void a warranty in and of itself. As long as you do not damage the product during your maintenance of the product, the warranty should remain intact.
Where this gets tricky for computer components is that the manufacturer may argue that your changing of the cooler could cause it to operate out of their original specification and if the card were to be rendered inoperable, they may pin the blame on your modification. You'll want to reach out and get clarification on this/read the fine print of their terms in order to determine if such a clause exists in the warranty. For GPU's in particular, most are fine with allowing users to install water blocks on cards without voiding warranties, but damage occurring as a result of a water leak would still void the warranty.
Do also keep in mind that if a manufacturer does allow you to upgrade your hardware without voiding warranty, they may still have terms that require you to restore the card back to its original configuration prior to shipping it out for warranty support.
I've included an example of one of our protection plans terms below so you can get an idea of what common terms look like. The context for the below quote is "limitation in coverage as a result of":https://60a99bedadae98078522-a9b6cded92292ef3bace063619038eb1.ssl.cf2.rackcdn.com/documents_MCCESTC09.13State.pdf
Damage resulting from unauthorized repair; software virus; or electrical wiring and connections; damage caused during delivery or removal, improper installation, or setup including, but not limited to packing, unpacking or assembly, user facilitated minor adjustments and settings outlined in the product’s owner’s manual, external antenna or local reception problems, inaccessible products or parts, negligence, misuse or abuse whether willful or not. Repair of resolution (pixels) failure must match the factory minimum standards before an authorized repair occurs
The "unauthorized repair" portion pertains to taking it somewhere else, that third party breaking the product, and then trying to get it covered by our protection plan. The portion highlighted in bold is what would specifically pertain to your question in regards to modifying a product with an aftermarket cooler. If you were to damage the product due to improperly installing the product (or an upgraded cooler on said product) or during assembly of the product, the protection plan would not provide coverage for the damage.
Hopefully this makes sense. I would recommend checking with your GPU manufacturer for more details on their warranty terms and if you have questions about one of our warranties, I'm happy to clarify if needed.
I understand you are concerned about your temperatures, this does appear to be common for load intensive games, though I would check with PNY directly about any warranty violations for several of the reasons Michael mentioned earlier regarding potential damage from the modification, or needing to revert the change before warranty claims.
Their support options can be found on their website at https://www.pny.com/support
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