I haven't used my espresso machine in a while because it occasionally blew a fuse. Upon inspection, I found some leakage, which I am currently addressing by disassembling, cleaning, and sealing all connections.

I also examined the Fluid-o-Tech roto pump and noticed that the outer bearing is deteriorating. Therefore, I might need to replace the roto pump once I've addressed the leakage.

What do you think caused the fuse to blow? Could the leakage have led to a short circuit, or might there have been excessive resistance in the roto pump?

Far more likely that the water caused it than the bearing. Those things can stall on start up for a couple seconds without the motor drawing enough to trip the breaker. (Remember, when it's trying to "boiler-fill", it's not trying to heat either boiler, so it's not drawing anything close to the "15 or 20A" that it is allowed.)

Thank you for your feedback. My intention is to securely reconnect all connectors, ensuring there's no unintended water leakage.

Most of the wires, except for the ground, are encased in white plastic protectors. Do you know where I might source these? Some of them, especially those exposed to heat, have become brittle and are cracking. If I can't find replacements, what would you recommend using? Shrink tubing? I'm uncertain about the precise English term for the plastic protector.

I would call them Faston Insulators, or Faston Boots...
https://canada.newark.com/te-connectivi ... price=true
They're available at any electronics stores or hobbiest places... Like Radio Shack if they still existed... In my neighborhood we'd go to a "Sayal" https://secure.sayal.com/STORE4/
There will be something similar near you. Or just find an online retailer.

BaristaBoy E61 wrote:Shrink tubing should be fine. Is your outlet GFCI protected?
Water leakage is the likely cause of an occasional fuse blowout.

Yes, all my outlets are GFCI protected.

The photo in post #3 shows discolouration and maybe a bit of charring. This is not normal heat damage, which simply causes brittle plastic. This sort of damage indicates localized heating, usually caused by a corroded or a loose connection. You need to take a close look at the connector on the black wire and the matching male connector onto which it mates. If I'm right, you need to replace that female connector and brighten up the male counterpart; a brass brush is ideal for this, but a bit of crocus cloth will do too.
PS, this is unlikely to be the cause of your fuse blowouts, unless your load centre has an arc-protected breaker on that circuit. However, if you just reinstall that connector with a fresh boot, you'll soon enough have another problem to repair.

crocus cloth??

My opinion (and just that) is that if one needs replacing because of corrosion they all need it (or soon)...

If the heat that has darkened the faston boot hasn't yet made the insulation on the wore hard and brittle, then the wire is okay, but it would be good to determine the source of the heat. If the faston inside the boot is making good resistance-free contact, then carbon on the switch's contacts is the issue and you could consider cleaning them to hope to get a few more months use while you await the arrival of the replacement. (You could measure the resistance through the closed switch for peace of mind).