Tow bar fault
 

When I ordered my xc90 I ticked the option of tow bar , everything worked perfectly until last September on the way home I heard a clunky thudding noise, so much so that I pulled off the motorway onto the hard shoulder to check everything out, all seemed ok & we carried on home with the thudding noise.
The caravan was put away for the winter & I never gave the issue a thought until last month when I brought the van home from storage & the thudding noise was still there.
One of my neighbours is a caravaner with the old shape xc60, we used his car to tow my van & there wasn’t a sound.
I took my van in for its service 2 weeks ago & thud thud all the way to the service guy. He let me tow one of his vans to make sure the noise stayed with the car. Sure enough it did.
The car is out of warranty (over 3 yrs) & it’s going into volvo tomorrow for the tow bar to be checked out, hopefully they find a fault & fix it for free , when you think about it the tow bar is seldom used & for a whole year due to covid restrictions it wasn’t used.
I really don’t want to fork out another £1200 for a new towbar.

I took the car in to taggerts (lookers) Glasgow this morning, I saw the service manager Russel. A really helpful guy, the car was taken into the workshop & the bumper removed & all the fixings on the towbar were checked, unfortunately everything was ok.
This job was done FOC, I then took the car to the caravan storage & took the van out for a run, unfortunately the thudding noise is still there.
I don’t know what to do next , volvo say the car is ok & the service engineer says the van is ok to.

Go into the garage with the van and demonstrate the noise? Also if you grasp the tow bar and strongly lift the car up and down on the suspension, does it knock?

There isn’t any noise from the towbar or the hitch of the van , I can hitch up & use the jockey wheel to raise the car without noise.
I’ve used a friends car to tow my van & there isn’t any thudding, I’ve also towed another van & the noise is there. That’s why I was convinced it was the car. But the dealer says the car is spot on, I’m reluctant to put an other tow bar on @ £1200 & it doesn’t fix the problem.
This is my 6th new tow car & I haven’t had a problem like this before.

Is there movement between the ball hitch and the caravan towbar ? In other words is the caravan "balancing" on its axle/s when I believe it should be nose heavy for correct towing ?

Edited, looks like you beat me to it with the previous posting !

The noise originally started while I was towing home last September.

Ok, different car and different towbar, but my last car was a xc70 with removable towbar (current is v90cc with electric). But the 6 bolts that for the towbar unit to the car’s chassis came loose causing mine to bang on bumps, acceleration and braking. Towbar was fine. Had to pay a garage £40 to fix it because I didn’t have that big a spanner’s with me on holiday. Is there any movement in the towball?

It’s the electric towbar I have, it’s a solid as a rock , that’s what’s perplexing about this whole situation, as I said before the dealership took the bumper off today & made sure all the fixings were ok, the engineer didn’t get any movement on any bolt & said it’s safe to tow with.

Have you checked the diameter of the towball?

If it is warn then this might explain the noise!

Appreciating the fact you have tried a combination of tow car and caravans to try to replicate the noise etc but have you tried simply greasing the caravan drawbar.

When ever i get any thudding i know its time to get the grease gun out and the give away is vertical play when you grab the hitch and lift it up and down. We tow around 2K miles a year and grease the draw bar probably 3 times between the annual service.

Whats to say the caravan you tried also needed greasing or the XC60 may have sat differently imparting different forces via the hitch...its worth a try.