Hi there I have a 1999 Subaru Forester, yesterday it was 40°C (104°F) weather in Australia and my car was sitting in the sun all day, so the car was probably over 80°C (176°F). I got five minutes down the street and my car started making the most horrendous high pitch squeeling noise, it sounded like metal scraping against metal and it would lower in volume and vice versa. It wasn’t a consistent noise, it would sound like it would rubbing and then it would grind, if that makes sense. I touched the wheels to check if they were hot but they weren’t overheating. It didn’t make the sound when I reversed or was in park. I’ve just had all the break pads and rotars fixed and replaced. Today is much cooler and I went for a drive and the sound had gone. I’m nervous to drive it to work as that sound was horrible but I kinda have to. Is there anyway to know what that sound could of been??
I had a problem, also in Australia, also in extreme heat (only in summer) where the car driving/timing belt (or something) was drying up and started squealing, but it wasn't at all like metal, it was more like very high pitch humming. It may be completely coincidental, but here is a video of my issue.
I went down to a mechanic to check it out (we thought it might be the belt) and they pretty nicely took a look at it and he said he just greased it a tiny bit rather than replacing and everything was golden.
It happens a little bit in dead of summer these days, only when I'm stopped. Video should explain it.