HOW TO REMOVE PETCOCK - 1998 Buick Regal

There is a mesh filter built into the petcock on the tank. It's up inside the tank. You would have to empty the tank of fuel BEFORE you remove the petcock tap.
There might be an 'inline' filter fitted as well. Start at the petcock and follow the fuel lines to the engine. If one is fitted it will be a small tube shaped insert in the middle of one of the pipes. Something like the image below.

Bleed tank, remove petcock and replace.

DON'T. They always crack. If they don't crack, then they leak when you close them. If you want to drain your radiator, remove the lower hose. No pro ever uses the petcock

Some cars don't have it, if this is the case you have to remove the lower hose, refer to the manual of the car or a dealer to see if your model have a petcock valve.

Only option is to remove and replace petcock.

Place a drain pan under the petcock.
Slowly turn the petcock CCW
Be careful to avoid contact with the flow if the car is hot
Open the petcock several turns until the flow is constant.
Remove the radiator cap to allow air into the radiator
once flow has stopped, close the petcock.

Is there anything more we can help you with?

open petcock at bottom rear of radiator. if not petcock, remove lower radiator hose.

If you can remove it, you can replace it either with the correct size NPT pipe plug or another petcock. I generally use a plug with teflon tape on the threads and drain by removing the lower hose...It's faster and easier than using the drain!

You will need to remove the radiator cap. Then you need to locate the petcock (drain plug) on the bottom of the radiator. Remove the petcock by carefully loosening it. You may need to use a pair of pliers but be careful not to break the petcock. When you reinstall the petcock make sure not to over tighten it, it should be snug but not tight.

Most are difficult to get to and so many don't work correctly that it it's almost silly to even use it. Far easier is to simply remove lower hose from radiator. It works better and faster. Just be careful though...Don't do hot or you may get an unwanted scalding bath!!