It fits round the bottom of the valve to lock the lid when pressure is built up

pressure use a 1/4 turn of the top against the bottom to undo the locks after the pressure in the pot has been released by removing the safety valve
any pressure at all in the pot effectively stops the lid from turning

Picture?

Make and model number?

replacement parts can be found easily on amazon. here: Amazon com OXO Good Grip Pop Container parts I hope this was helpful. Cheers

The problem that you describe is more likely the check valve. Follow the air discharge tube from the pump to the tank. The brass or aluminum fitting at the tank is the checkvalve. Clean debris in valve or replace valve with generic. Should cost about 20 dollars. Make sure that the air discharge tube is clean of carbon deposits so that the new valve will fail. Good luck

just buy a new cooker

Typically the lid seal has an opening all around the center and it must face up and fit inside the lid, once is fitted inside the lid cover, lubricate the bottom of the lid seal with soapy water and place it on top of the pump casing. Then apply pressure at the side tabs to snap the lid back in place, note that you may have to use a big C-Clamp to be able to put the lid back on.

I think E2 means open circuit in thermocouple in center of bottom. E4 means no contact on pressure sensing switch at edge of bottom. Mine had E4 error. Took out switch and used fine sandpaper to clean contact points. Now it works fine.
Remove 3 screws in bottom. Remove bottom cover by turning it ~1/4" to clear tabs. Remove switch at edge of bottom with two blue wires going to it. Clean contacts and replace.

Removed the 3 screws on the bottom. There is a relay near the circuit board. Kind of looks like an old morse code relay. Just tapped out "E 4" in morse code. Plugged it in and it works fine.

That's right you will need New Black lid Actuators fitted top and bottom also new retro link supports if you still have the factory plastic ones and maybe a new RFI module if you'd had a F1 fault. Sounds like you've been told this, so now all you need is to get quotes for all these parts to be fitted at a cheaper price. cheers

Before you attempt to dismantle the Bosch Tassimo, you need to determine how/where it is leaking. (1) Before making a drink with the unit remove the cup tray and ensure the bottom where it fits is dry. Replace the drink tray (2) Make a drink or use the cleaning disk, put a cup under as normal and start the cycle. (3) After the drink is made or a clean cycle remove the bottom cup tray and see if the bottom where it fits is wet.
If it's wet you have two (2) problems
(1) The pressure valve on the top of the heater is staying open, usually due to using water that has lots of calcium in it. (2) The pipe that leads from this pipe to the bottom tray is leaking (it's not a good fit in any of these machines, and causes water to drip from underneath.
Don't take it apart yet! Buy some de-scaler from AP-Wagner.com and run this a few times, it should clear it. If it doesn't you have no choice but to open the thing.
If you have the model with a filter use it and change it when it tells you. If you don't have a built in filter, don't use water directly from the tap, run water through a Brita filter or similar
If the bottom tray doesn't get wet, take it apart to see where it's leaking. 99.99999999999999% of the time it the valve.

So how to take the thing apart.
(1) The sides (silver or black) slide to the rear. However, you have to put something in the back between the side and the rear cover to pry them apart while pushing to the rear. It's very difficult. I use a 6" steel ruler. You have to bend the sides to overcome the catches that hold them in place. You'll see a small rectangular slot at the back of each side. They will come off eventually.
(2) Once off you'll have to remove the lid where you put the disc in. Remove the 4 screws under the lid deck. (3) Remove the water pipe screws (2) and the bar code scanner screws (2). Be careful of the barcode scanner the cable is very, very delicate (I always unplug it from the circuit board and remove it completely, lift the black tabs at either side of the cable). Lift of the lid assembly. (3a) Remove the screw from the underneath the unit at the back, this allows the front to move out. (4) At each corner of the top carefully pry the locking mechanisms until the top is free. Remove the pink (thick) pipe and the pink (thin) pipe and turn the top around out of the way of the heater unit. A coiled steel spring will drop out, it's easy to replace when the top is back on. (5) Where the thin pink pipe goes to is a back pressure release valve carefully pry the clips apart and remove. Take out the rubber O-ring and the valve. Carefully remove any calcified deposits from under the rubber (blue) valve. (6) Reassemble valve (7) Reassemble top, and lid taking care with the bar code reader. (8) Test before replacing the sides
The thick pink pipe that descends from the top, that you removed earlier goes to the bottom tray, you will notice it is very loose (they all are) and it leaks. Put a tie wrap around it to seal it.
Good luck, it's not an easy fix, they were never meant to be taken apart to be repaired - not very ECO friendly. Let your MP/Congressman know, these should end up in a landfill because of 50 cent valve, and they don't come apart.