MACHINE GETS HOT ON TOP RIGHT HAND SIDE.TRYING TO LOSE VENTILATE

Try this, push in on the knob when the flow stops, if that works, then the tap rod needs to be replaced. If your machine has the plastic steam valve assembly, try to get the stainless steel steam valve, I noticed that you have replaced once.

This means the water cannot flow through the machine. Normal fix is to prime the machine (turn water dispenser on, fill a cup) or descale the machine. Go through the menu, select descale, enter, then turn the steam knob fully anti-clockwise. You should put the descaling solution in the water tank first.
If you have the auto-descale in the menu then run it. Run the solution through the machine twice. Then rinse well.

The steam valve assembly that the steam knob on the right hand side connects into is probably faulty. When you're steaming if you hear hissing coming from behind the knob then this indicates the connections into this assembly are leaking steam, and also hot water, which is why you're getting puddles under the machine. You can get a replacement steam valve assembly that fixes some issues with the original (part code SVM-17, available from www.partsguru.com) and will prevent the leakage, or you could simply try opening the top of the coffee machine and removing the tube that runs from the boiler into the steam valve. It has two o-rings that provide the seal where it connects into the steam valve assembly, and if you lubricate these with a food grade silicon lubricant it may fix the problem. My Gaggia is 7 years old so I decided to replace the whole assembly which costs about $50 and that solved the problem completely.

Try this run the hot water cycle for a few seconds, it that works, try steaming if you get the message again clear it by running the hot water cycle and then go to steaming, this time push in on the knob after you open it, it that works, then the tap rod or the valve assembly needs to be replaced.

Check the end of the steam wand, that could be blocked, if not then try this push in on the knob after you turn it open if that works, then replace the steam valve assembly.

if you open the side valve to let the steam go out or to ventilate you say it leak under the machine try it agan it look like a leaking pump

There is an air lock in the hydraulic line of the machine, thats why it is calling for ventilate, if hot water valve is open and it is still calling for ventilate, then it is possible that the valve is blocked, it might be at top of the wand or at the tap rod assembly.

Try this, after opening hot water valve, push the knob in when it asks for ventilate. If that works then contact your nearest gaggia distrubutor and ask for a new stainless steel steam valve assembly.

The leak is most likely from the steam valve, you will have to either buy and replace the o-rings and the pistons in the valve or just buy a new valve assembly and replace it. Easiest solution get the new valve assembly.

The steam and leaking in the upper right corner turned out to be a leaky valve. I may have been able to fix it by just replacing the O-rings. However, the only place I found to get the right rings was in the kit to replace the steam valve assembly.