Cause and Effect - Did mechanic cause new issue with car

I took my mustang to a mechanic two weeks ago because the car was not producing heat inside. They said it had to do with the coolant cap and charge me $100 to fix it. Yesterday, the car started to smoke and I took it in again today and was told that coolant and gotten onto belts in the car and started melting them. It seems a little to close to them working on the engine two weeks ago and the car all of sudden having issues. The bill is now up to $700!!! If this was caused by the mechanic not tightening things properly then I would like to know. Thanks!

Did you get it fixed or is it an estimate? You can check to see if the belts are tight yourself. But it’s too late if the work is already done. What year Mustang? It’s really about the coolant, but I’m not sure whether you know what type is used. It’s probably ethylene glycol, but want to be sure. If it is ethylene glycol, it is compatible with many rubber materials.