Can modem goes dead?

I don't know how to say this but I am feeling that my internet connetion is slow. I like to know can modem goes dead?

If the interent connectoin is bad can it be due to the room as its hot and I didn't turn on the fan or air conditional. Trying to save cost but later on I see that the modem is like burning up.

I am using ADSL modem. I used to have a CPU with internet inside but later on I think its spoiled and didn't get it to fix at all. That's why I bought the modem. I think having the external modem is better as we can see it. If its internal like my CPU I can't see it and no idea why it just spoiled.

Tell me what you think.