Sell the server as fast as you can and buy a different brand. HP has no interest in supporting their servers, especially older ones purchased second-hand. They have switched to a pay to play business model to try to create a constant revenue stream and nickel and dime the IT budgets of companies. As such, you have to have a $500+ per year service contract to even download the main BIOS for your "new" server.
The most likely cause of your fan noise is using a non-HP hard drive, which is another "feature" they have conveniently built in to convince you to buy their overpriced, rebranded HP hard drives. HP die hards will claim it's because third party hard drives don't properly support SMART in their firmware, but shockingly, they work just fine in every other computer out there without fake overheat issues.
There's a reason all of these HP servers are flooding the second-hand market and are cheap as hell. Back in 2014, they announced their paid-only updates (except in Australia where it's illegal) and IT pros have been dumping them left and right ever since.