Power loss, hissing noise and burning smell Mk1 Mondeo

[DocSteve]

Hi - posted this in Ford but prob should have gone here.

Have recently bought a Mk1 Mondeo estate with possibly only 50k genuine miles on clock. Anyway, only issue was a temp gauge that seemed to be reading too low. Took it to Halfords autocentre and they checked all cooling system and replaced the temp sensor. They reckoned rest of the car was in good shape. On taking it out of the garage I immediately noticed a lack of power and a hissing / scraping sound coming from under the bonnet on acceleration. I pulled over and noticed a smell of burning. Can't see any leaks or obvious damage. The noise seems to be originating from around the cambelt area.

I am obviously taking it back to them tomorrow but want to try and form an opinion of what they could have done to it in order that they don't try and claim something not relating to their work. It seems quite odd that it was fine when driven in this morning and now in this state after being in the garage!

Any ideas most welcome - I am struggling to tie this together. It's dark and I can't really see very well under the bonnet unfortunately.

Thanks
Steve