hi i just bought a 2002 seat ibiza 1.2 and when i accelerate it makes a noise like a quiet thud and is onyl when i accelrate the garage believes its nothing to worry about and left it at that and i just wondered if anyone could let me know what it is its only done 57000 miles the garage said it could be the engine mount but i just want to make sure and get it sorted
thankyou for any reply or help

also when i put clutch down and up but dont do the noise everytime