Inside of microwave top peeling and blistering

Most likely if the metal screen in the door is intact. That screen and the metal cover on the back and sides surrounds the insides of the oven reflect the microwaves back into the oven. Just be careful about the peeling plastic inside.

If the oven is working with good heat all you need is to have the machine serviced. the ceramic coating of paint on the inside of the microwave must have corroded and so the blisters can happen. Due to this the smooth surface within is lost and so the roller make a higher noise.
Take the micro wave and clean and scrap off all blisters before a good coat of ceramic/nonmetalic paint is used.

Yes you can repaint it. Use an epoxy based paint and clean the metalwork with sand paper first.
The only health question is if you get the flaking paint in your food - yuk!

i think you might beable to repair it, i found this http://www.designsbysylvanye.com/id66.html. its for art microwaves i guess but it might work <3

The paint plays no role in protecting you from the microwaves. The metal case is what contains the radiation, so you should be just fine.

No, if the cavity metal of the oven is chipped or charred, it will have to be sanded smooth and clean and dried thoroughly.

Then you can apply some high-temperature appliance paint, available from places like Wal-Mart, Lowe's or Builder's Square.

Otherwise, you can have rust and arcing, which can be messy.

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It would be dangerous to do so. Any exposed metal inside a microwave is source for sparks and is extremely hazardous. I would recommend getting the paint job done up, or even better, buy a newer model.

That clear cover (sometimes called the inner door screen) is very important.

It protects the metal mesh / screen from debris and corrosion. The metal screen allows you to see "what's cooking" (*grin*) but prevents microwaves from leaking out of the door due to the precise size of the openings in the mesh.

If the mesh rusts or gets grease or food on it, it can arc, and this can damage the screen, then microwaves can leak, causing a burn or fire hazard. (No "radiation" threat, though)

If no arcing or other damage has occurred yet, you can clean the area squeaky with alcohol, then dry it completely and use the smallest possible amount of clear Scotch tape or packing tape to cover the tear and make sure it's flat.

If this fix doesn't work, or it's too big an area, you will have to replace the sheet, which can be ordered.

You'd have to heat it up with a hair dryer, peel it off slowly, then clean the area with something like acetone, then peel and stick the new one.

If you need to or prefer to order it, I would need your brand and model number to help you further.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

I do have the same problem, but I know they make microwave paint if you can get it from an appliance store or you can order through the web - BUT 2 sites I just looked at said a gloss enamel paint, such as that used to paint "model" toys works just as well. In either case: Smooth the old stuff off, sand lightly (you want no metal dust left -or- damaging any coating on the metal) just sand enough to make sure there's no flakes & it's smooth, then use a gloss enamel paint rather it's approved for microwaves or the Testor's kind.
NEXT -Make sure you DRY with Hairdryer to set the paint, and keep the heat to med or low, don't bubble or scorch your work!) and do not use the microwave for 24 hours!! Leave the door open while drying for several days afterwards if you can. Any fume smells can be absorbed by using -used- coffee grounds and leaving overnight. Google groups was one source the other was a repair listing forum.

Here is a link to buy the paint.
If the microwave is not creating a spark inside when in use, It's OK to use.