Rear suspension loud bang.
 

I tow a caravan with nose weight about 90Kg. I am confident there is no caravan suspension fault and it is only 3yrs old.
Several times this year since summer, I have towed over large bumps or dips in the road unexpected at speed I wouldn't if I had known about it, and the car suspension has had a real thump as you would expect. I have had a Volvo dealer annual service and MOT and neither can find anything wrong with the suspension. the loud bang every time I accidentally drive over any unexpected obstacle like a hidden speed bump or hidden dip, is very alarming. I'm a bit past having a go at it myself as I certainly would have in years gone by. has anyone got an idea what the issue may be?
By the way, I think the loud bang is not the initial shock impact but the suspension reaction a split second after. I have even had the caravan checked to see if the body is coming loose on the chassis (which has been known on some caravans)

sounds like suspension topping out ... no rebound damping. how old are your shocks ?

I had the caravan body come loose from the chassis. There was no noise but I could see it moving in the rear view mirror a couple of times after it had gone over a bump. Fixed twice under warranty and I was not confident that it was fully sorted so I tried the van in.

If you are getting a loud bang then it is most probably something on the car!

Is your jockey wheel fully up? If not fully wound up and tight it might have come loose and wound down and botted out?

The car is 10 yr old, but only 68.000 miles. Weve had it since it ended a 3yr Motobility lease with 18,000 miles and was immaculate, and still is. I have it serviced by the Volvo dealer apart (from 2 yrs). however weve towed a bit and at that age I wondered if shockers were due. No comment from the service people though.

I might just replace them anyway if its not too much £.

I'd get all four road springs checked. They can break very low down in the spring seat, which can be hard to spot. I had a Saab which broke both a front and a rear coil spring at diferent times. When the front one broke it took two visits to diferent garages to get the problem diagnosed. Although there was a clonk when the front of the car went over a bump, the noise was much more noticeable when the rear wheels hit a bump or a pothole, so at first everyone was looking at the wrong end of the car! The first garage missed it altogether. I had also had a rear spring break on our little Nissan Note, and that was only found when I picked up the broken piece from the driveway and realised what it was. It has broken so low down in the seat that the ride height was not noticeably affected.

I was told that the weakest part of a road spring is deliberately engineered into the lowest turn so that if it does break the spring should stay contained within the spring seat and not fly apart and damage the tyre. That does sound sensible to me.

Jack

What car?
Given its 10 years old the recommended limit nose weight on a v or xc 70 is 75kgs not 90 according to my 2009 xc70 handbook.
It may just be the jockey wheel grounding. Other than that a broken spring which has been mentioned already.

Paul.

Shocks fail at anytime after 50 k . Also check the rear suspension rear trailing arm front bushes . Typically these make an irritating squeak but can make a very loud bang if de-lamination is bad . These again cam fail from 50 k but main culprit for failure is ust causing the rubber bushing to de-laminate from the bush housing . many mot garages miss it as its behind a plastic cover whic they are not allowed to remove . Not dangerous but can make the back of the car feel loose and noisy .

Thanks green van man. The car is MY2010 SEL with 90Kg limit according to my handbook. I've always towed with the caravan loaded so that the nose weight is dead right according to my Reich weighing device at 90Kg. Never had a problem until a few months ago. The banging was awful on holiday in France and again Sunday towing home after a weekend away. The nature of the dip in the road and towing speed was not such that there should be any drama, but again the banging was loud so something is certainly wrong. By the way, the back seat was empty and very little gear in the boot. I've towed with the boot fully loaded and much heavier.. I had the MOT place check it over again on the platform today and they can't find anything wrong but they didn't use any pinch bars or anything to look for wear so I'm not sure they were really that interested.

it is also possible that your top shock mounting may have failed . its an easy fix check them when you check your shocks they need to be removed to check them properly

Seek and ye shall find........eventually
 

Evening Ern, Have you checked the tow bar fixings under the car? if not would suggest getting under there with a torch or inspection lamp and looking for something loose or even cracks in the sheet metal. Good luck in your search.

Regards,Keith.