Random knocking noise

[Sleedale]

Ok, I've searched the threads and the wiki, and actually found few threads on knocking sounds and had some suggestions investigated by a couple of different knowledgeable mechanics.
Apparently nothing is about to drop off, which is a relief, BuT

The strange noise started randomly last year. We were happily trundling along and out of nowhere came a knocking sound from somewhere under the floor, towards the rear near side wheel area - I think. We stopped, I phoned a mechanic, checked as much as we could, then set off again, very carefully - nothing, no noise
Next day, trundled around the area then set off home, did quite a few miles, steady 40 mph, knocking started again. Stopped, checked, set off - nothing, no noise.

Ran the van for a few more weeks, no noise. Then it went into rest.

Back on the road, this month. Drove it 8 - 10 miles and the noise started again. Into the garage and asked the knowledgeable guy to see if he could find it.
It's not:-
CV joints or anything CV
Wheel bearings
Drive shaft
Nothing is loose, nothing moves, he couldn't find anything.
Out today, it mostly happens when the accelerator is pressed, seems to stop when no throttle applied.
The knocking seems to speed up as speed increases, but will stop and start randomly.
I spent a short trip with my head in the 'toilet' cupboard under the back seat, nearside, and it seems to be somewhere around there, but short of hanging out of the sliding door with my head under the van when it's moving I can't be more specific.

So, I'm sure someone has come across this before, will grin, and say, "oh, that's xxxxxxx"
We are off to deepest, darkest Pembrokeshire in a week and a half, and it'd be really nice to get there with everything in one piece, so any ideas our local guy could check this week would be really, REALLY gratefully received.

[mark]

had this on my bay, it started as a slight knock that would come and go, ended up as though someone was smacking the under side with a lump hammer which also came and went. after pulling it to bits more than once. it did it while not under load and putting the wheel back on, and it turned out to be the inner rear wheel bearing.

mark

[Sleedale]

Thanks Mark, first suggestion written down to be checked

[ade700]

i had this it was the cv joints on mine

[California Dreamin]

CV joints is the most obvious & likely.
Castlelated nuts not tight ENOUGH on drive shafts ...500NM.
Brake shoe retaining spring broken allowing the show to touch the drum.
Engine or gearbox mountings seperated (less likely given your symptoms but worth checking)
Wheel bolts/nuts loose.

Martin

[Oldiebut goodie]

I had exactly the same from the nearside rear - a visual check revealed nothing but eventually the outer cv joint failed. As said ^^^ most likely candidate.

[Sleedale]

Well, took Victor to see the van doctor today. The knocking started almost immediately from setting off, although not loud and not consistently, but by the time we got to the garage it was still making the noise - van doctor jumped in and listened, and thinks it is probably the wheel bearing going. So, Victor is going in on Wednesday to potentially have a bearing changed, and if its not that then hopefully, having heard the noise other things can be checked have high hopes and it needs sorting as I don't want to be stuck half way to Wales next week with two woofties next to a motorway
Oh, by the time we set off home, so after around 15 miles the sounds got louder and more scary, but when we stopped for a few minutes to chat to a neighbour, and set off for the last 300 yards, no noise! So, it makes the noise when it warms up, gets louder it gets hotter, worse when accelerating and kicks off especially after left hand bends.
Fun these van, aren't they

[California Dreamin]

I'm not sure whether I've ever heard a rear wheel bearing that could be described as making a knocking noise!
Wheel bearings by their very nature, usually make a constant humming noise who's tonal pitch, starts off low and gets progressively higher with speed. Wheel bearing noise is often effected by load, so for instance, if you take a fast left hand bend and the intensity of the sound decreases you know the offending bearing is on the left hand side. Swapping to a fast right hand bend would load the bearing more so you would then expect the noise to increase.

I hope that your mans diagnosis hits the correct part early sooner than later as your repair costs can mount up quite quickly on route.

Martin

[Oldiebut goodie]

I would have him take the nearside outer cv joint off (if there are any bolts left ) to check it - the description fits cv joint perfectly, exactly as mine was, very loud,stops for a while then starts again randomly, which luckily gave up only 1/2 mile from home. You will lose all drive if it is the cv joint, mine had all the bolts sheared so visually it checked out as OK.

[Sleedale]

Thank you both for comments, I will ask him to check/look/take apart the cv joint as well

[sarran1955]

Hello,

This might help.....

https://www.youtube.com/watch?v=meTNBph3rUU

Cordialement,

[Sleedale]

Hello,

This might help.....

https://www.youtube.com/watch?v=meTNBph3rUU

Cordialement,

Excellent video, very clear, you make it look so simple hopefully lovely mechanic can sort it out, either bearing or cv or whatever it is.
Took it in today and of course no noise at all having sounded like someone breaking through the floor two days ago. Just hope it's something obvious and fixable - off to Wales next week

[CovKid]

A seemingly random knocking noise can occur due to a worn bush where the bottom of rear shock absorber meets trailing arm. I mention this as I've had a noise for ages and simply couldn't find it. MOT picked it up straight away. Other causes are worn/split/broken engine mountings. Not saying these are your problem at all but anyone else reading this and struggling to find the cause of a knock and have ruled out worn CV joints would be well advised to check these areas.

[Sleedale]

A seemingly random knocking noise can occur due to a worn bush where the bottom of rear shock absorber meets trailing arm. I mention this as I've had a noise for ages and simply couldn't find it. MOT picked it up straight away. Other causes are worn/split/broken engine mountings. Not saying these are your problem at all but anyone else reading this and struggling to find the cause of a knock and have ruled out worn CV joints would be well advised to check these areas.

Definitely worth noting, we could do with a wiki section of 'symptoms and possible causes'! Mind you, it'd probably be a very long list of 'it might be' for each symptom

We, however, appear to have swapped a knocking for a grinding/grating had a new wheel bearing and inner? cv joint etc, drove it home day before yesterday, took it for a decent run today, to make sure the random knocking had gone. Not a huge long journey, but no knocking, but grinding instead. Tried to contact van doctor, couldn't so took it to our local mechanic who loves old vehicles, and he tried a couple of things but thinks its the bearing not set properly, or something like. So Victor is still messing us about, off back to van doctor tomorrow. I think he prefers to be indoors in this rubbish weather, we still have lying snow local man half jokingly said he'd buy it, loves VW campers and all things old, and I was very, nearly, almost tempted maybe be all better tomorrow

[Oldiebut goodie]

My neighbour Phewgot had a grinding noise - I tracked it down to the brake backplate had had a knock and was rubbing on the brake drum. Worth looking at as you have had work done that could have caused this.
Chock your wheels, handbrake off, jack up your wheel, turn your wheel by hand and see if you can hear /feel rubbing on the backplate.