cistern leaks only when flushed

[Jupiter01]

I've got a close coupled toilet. Every time it is flushed, water seeps out from where the cistern connects to the pan. Is this the doughnut washer and why would it suddenly start doing this?

The bolts holding the cistern down are nylon and don't appear to be involved.

I'd appreciate your thoughts on this.

 

[denso13]

Is this the doughnut washer and why would it suddenly start doing this?

Probably, they don't last forever unfortunately.

 

[Jupiter01]

Probably, they don't last forever unfortunately.

Sure. I just didn't expect a sudden breakdown. It was fine and it's now ****ing it out. Technical term...
Again, only when you flush.

When you fit a new one, should I use any lubricant/sealant?

Thanks again.

 

[denso13]

When you fit a new one, should I use any lubricant/sealant?

No, not required.

 

[dilalio]

Sure. I just didn't expect a sudden breakdown. It was fine and it's now ****ing it out. Technical term...
Again, only when you flush.

When you fit a new one, should I use any lubricant/sealant?

Thanks again.

No sealant (although Plumber's mait is sometimes necessary) but try and match the existing donut as there are quite a few varieties.

 

[Jupiter01]

UPDATE - replaced the doughnut washer and issue has been fixed. Thanks for your advice and comments. Much appreciated. Here is a pic of the old washer.

One further question: the screws inside the cistern holding it to the wall, are rusted and slip through the holes in the cistern. Tempted to use new screws with washers but presumably they will rust too. Can I get some advice on this please.