As jon@work says is the pump running, making a whirring sound ?, it should stop after 20-30 seconds or so, if it doesn't there is a problem and if it runs continuously it's going to make it kin hot as it's not supposed to, has a very hard job to do.
If not whirring to start with and getting hot it is seized, so just have a listen, they're not quiet so will easily hear it even with bonnet shut.
tabetha