VECTRA PROBLEM - Strong/ violent thud when switching off engine, can you help please ? Thanks

[Fastlife91]

Car, Vauxhall Vectra 1.9 cdti 120 bhp.
Having an issue that has been occurring for about 6 months now, had it booked in at a garage but typical as it wasn't showing the problem as they were looking at it, yet it came back right after I got home.

Here is the problem.

A mechanic was poking around with a pry bar on drivers side wheel area ( the wheel was still on the car he poked the pry bar around it ) he was poking around near the fan belt area e.t.c trying to find the cause of a clunk ( different problem at the time ), not sure what exactly he was poking in that area with the pry bar but he said the mount seemed fine ( not sure how he could have checked the engine mount as I don't think you can get access to the mount just by poking pry bar around the wheel )

Right then from that moment onwards for the first time I switch off the engine and whenever I switch off the engine is a massive thud ( happens about 50 percent of the time, sometimes not as strong ). Been happening for months and caused the pulley on the alternator to rattle, then not long after the pulley burnt out and had to pay £100 to get a used alternator fitted.
The violent switch off still occurs, I'm worried it will loosen and damage more parts if it's not sorted soon.

It seems to be the thud is worse the longer the engine has been running.
It's probably similar to how a bad engine mount would feel on switch off, yet when rock the engine there seems to be no play.

Can anyone please give any ideas to the problem ? Thanks so much

[edgejedi]

Hi, I think you might need to be on the Vectra forums my friend....unless you happen to find a former Vectra owner her who might know.

Try here ? https://www.vectra-c.com/forum/forum.php?