Please help.... Brakes are squishy new master cylinder>>

2003 Toyota Tacoma my son purchased it for his first car. Brought it to the shop for squishy brakes they said it was a bad master cylinder. So they replaced it still squishy and now the shop is saying well IDK what's wrong with it. Well money doesn't grow on trees any ideas not looking to throw $$$ down a rabbit hole on what it might be.

 

I’d start with bleeding the brake lines, air could be in the lines. May require an quart or two of fluid to get all 4 corners. It depends where the air is and how much.

 

The shop claimed that was already done then wanted to change the calipers that they had already told me were fine. I get the feeling they think I'm a dumb chick who knows nothing.

 

research, this is a common and complex issue with Toyota trucks, I took mine to a Toyota dealer who used a BG brake bleeder machine on mine finally got it acceptable pedal, use the SEARCH function for help on it

 

This sucks. However, when ever somebody says can you help, this and that was done already. Unless, I really trust the person or group, I still have to start at the beginning. Not a professional auto mechanic, 30 years in computer/software. Trouble shooting is the same. You start at the beginning with the simple and obvious.