Steam boiler is leaking and I can hear a hissing sound when it is heating up. Kitchenaid has discontinued this product but I understand the boilers are Gaggia. Do I need to replace the Group Gasket?

You will need to test for where the power stops & check the fuses on each boiler for continuity. If you find any blown then replace the thermostat on that boiler along with the fuses. The thermostats are different rating for each boiler, don't mix them up. It's highly unusual for both boilers to fail at the same time. Occasionally one of the boiler elements can fail, there are 2 elements on each boiler, check them for continuity. If you have any boiler leaks then replace all the seals on that boiler, the steam one is the one most likely to leak. Buy your own seals using the old ones as samples from someone specialising in O ring supply. There are 5 seals on each boiler. Do not purchase rubber or silicone seals, only use Viton seals, they are high temperature.

You need to replace the boiler top that includes the elements. When one element has failed the other one stops as well if it is included in the circuit, it's the same as having a broken wire.

Test each element for the correct resistance. Check the thermal fuses for a circuit, they are held onto the top of the boiler with a screw down bracket. Check for a circuit through the thermostat.

Check the 2 thermal fuses on the top of the boiler, if they are blown replace them and the thermostat. While you are at it replace the seals in the steam boiler, there are 5 of them in that boiler. If the fuses aren't blown check the element for continuity, sometimes one will fail.

It sounds like you have the cup warmer turned on. But if that's not it there is a leak in a connection coming from the bolier. If you open it up it will be obvious where it's at. Don't wait too long because the moisture will effect the electronics.

Sounds like the safety thermostats on the machine is tripping because the machine is overheating or the circuit breaker is tripping because machine needs more amperage.

Relay will be fine if you fix the real problem. Get some new seals (5 of them) into the steam boiler and check for leaks from the teflon tube at the top of the steam boiler. When you have it apart tip it upside down, you will be surprised how much hidden water there is.

Hi
Machine 2 is the steam manifold leaking. You have to remove the hose clip in the back of the steam manifold. Remove the hose. Grab the trough in the back and pull up to expose the manifold. It will push out the front. If its white is very old, and if its black its a newer one. If its metal it is priobably the O-rings just need to be replaced. I still have the white one in my machine, because I cool the manifold off after using and that won't let it crack from the high heat after steaming. That is what causes them to crack.
Machine one, I would check under the red boot covers by the boiler for a bulge in the hoses. That is usually where they rupture. Make the new hose(tube) a little longer to prevent this from happening again.

It is possible that one of the 3 coils could be damaged, or there is alot of mineral buildup in the boiler, or the vent valve is not operating properly.
Try this, after turning the machine open one of the steam wands and leave it open until you hear a slight hiss with a little steam coming out. If that makes your machine heat up faster then the vent valve needs to be replaced, and your element is fine. If it takes just as much time, then the element is suspect.

Open the steam valve when you turn the machine on that will vent out the boiler, keep it open until it starts to hiss slightly and produce small steam bubbles, then close and machine should heat to temp. If that solves your problem then the vent valve needs to be replaced, until then you can turn using the steam valve open trick.