What could cause a massive thud when switching off the engine ?

[FastLife91]

Please help, this is so depressing and I am hating the moment when I turn the engine off because of it happening.

A ' mechanic friend' at the time poked a pry bar through drivers side wheel area to try find cause of a different issue.
I turned engine off after he did that to walk into the garden with him and it happened for the first time.
Immediately from that instant onward whenever I switch off the engine I can feel a massive thud.
however sometimes goes okay and switching the engine off will be back to normal completely smooth and can't feel a thing, then a few days or sometimes weeks later it comes back, a massive thud.
It caused the pulley on the alternator to rattle eventually it smoked and burnt out the pulley and the alternator had to be replaced and I am scared it will damage more parts.
I have had a few garages look at it and they can't find anything but annoyingly the thud isn't half as bad when it's in the garage or disappears completely and will all the background noise and vibrating from the roads it doesn't seem as bad.

More often than not the thud seems stronger the longer the engine has been running, but sometimes I can be driving hours on end and the thud will be only just noticeable.

Please Please can anyone read this and help tell me what it could be ? thanks.


edit : It happened the exact instant he poked pry bar through drivers wheel area so I am sure it must be related

 

[Lunchmoney]

Any chance you can take a video?

 

[FastLife91]

Any chance you can take a video?

Hey Lunchmoney

I have tried to video it but as it is more felt then heard the video didn't really reveal anything at all, though sometimes you can hear the thud as well as hear it so will try again, it depends on how well the camera picks it up.
Meanwhile do you have any ideas to the cause ?

Thanks very much

 

[Lunchmoney]

Sorry, not an idea at all right now. Thought a video might help others diagnose.

 

[Lunchmoney]

Does the car jerk forward when you turn it off? Like if you left it gear?

 

[FastLife91]

Does the car jerk forward when you turn it off? Like if you left it gear?

Hi, no it doesnt jerk forward or anything like that when I turn off the engine. Also it still does it whether or not I press the clutch pedal in at switch off

 

[TCJBOLDIE]

When your "mechanic" poked the bar in was the motor running and what is on that side that he may have damaged with his poking?
Does it still klunk if it is in neutral?

 

[FastLife91]

When your "mechanic" poked the bar in was the motor running and what is on that side that he may have damaged with his poking?
Does it still klunk if it is in neutral?

Hi
I am not totally sure whether or not the engine was running at the time he poked the bar through.
It doesnt do it at idleor in neutral, only once tbe engine is switched off you can hear the thud and when it is there it is a very strong thud, hence it eventually ruined the alternator, the pulley on it.
It seems the longer the car had been run the stronger the thud is, though sometimes I can drive for hours and can not feel it at all.

Thanks

 

[TCJBOLDIE]

Long ago back in my youth I had a strange sound that I could not find the cause so drove it to a workshop while it was making the noise turned the car off and when the mechanic came and started the car it had disappeared.

I eventually tracked it down to a broken alternator bracket, the one with the long slot.It was not obvious as it still appeared to be straight and perfectly in line/straight.

 

[Fabia17]

Carefully check your lower engine mountings. He might well have torn the rubber from its bonded metal. It will not necessarily be obvious because of the weight of the engine. It may well look perfect. But if you can place a piece of wood between a jack on that side of the engine and carefully jack the engine up to just take the weight, and then look at the mounting, you might find one piece of metal on the engine, or body, then an air gap, then the rubber, and finally another metal bracket. If this is the case, the engine mount needs replacing.
The mounting is a sandwich affair. A piece of rubber sandwiched between two metal brackets. One side bolts to the engine and the other to the chassis. There are usually two lower side ones, one each side of the engine, and one to the rear of the engine, also there is often one at the top of the engine towards the rear of the engine.... Check them all for damage and looseness. I hope this helps. If in doubt pop into a garage and get them to check them for you.

 

[lilleskutt]

Kan vara fel på ditt dubbelmassesvänghjul

 

[FastLife91]

Carefully check your lower engine mountings. He might well have torn the rubber from its bonded metal. It will not necessarily be obvious because of the weight of the engine. It may well look perfect. But if you can place a piece of wood between a jack on that side of the engine and carefully jack the engine up to just take the weight, and then look at the mounting, you might find one piece of metal on the engine, or body, then an air gap, then the rubber, and finally another metal bracket. If this is the case, the engine mount needs replacing.
The mounting is a sandwich affair. A piece of rubber sandwiched between two metal brackets. One side bolts to the engine and the other to the chassis. There are usually two lower side ones, one each side of the engine, and one to the rear of the engine, also there is often one at the top of the engine towards the rear of the engine.... Check them all for damage and looseness. I hope this helps. If in doubt pop into a garage and get them to check them for you.

Thanks, it was finally diagnosed after 2 years thanks to YouTube. It was a faulty throttle body, anti shudder valve not closing proper .

Not one mechanic or car garage suggested this, but YouTube did !

 

[Fabia17]

Thanks, it was finally diagnosed after 2 years thanks to YouTube. It was a faulty throttle body, anti shudder valve not closing proper .

Not one mechanic or car garage suggested this, but YouTube did !

Well, we all learn something new every day. None of us can know everything, and until we get feedback like this, we can often never know. Thanks for letting us know. Two years is a long time, but these often dark hidden problems are so obscure they rarely happen or come to the light.

Your feedback is invaluable for the future. Happy driving now.....

 

[daren301]

Witam, mogło to spowodować, że coś wpadło do silnika przez kolektor ssący, niestety nie sprawdzicie czy kompresja się nie wyczerpie, dobrze jeżeli kompresowania brakuje, tłok się stopił

 

[daren301]

Hello, it could have caused something to fall into the engine through the intake manifold, unfortunately you will not check if the compression is exhausted, good if there is no compression, the piston has melted