Resolved steering rattle: Loose bolt upper u-joint steering shaft

[Topocalm]

I thought I post this since I did not find this mentioned as a potential cause of steering rattle / noise problems in any of the many postings on this. I might be an outlier but hoping to help solve this issue should it occur in someone elses car.

Symtoms:
My problem was a rattle in the steering wheel that sometimes occurred at higher speeds from 60 km/h rather as a vibration, but it was always there at (very) low speeds on gravel or cobble stone or similar in the form of very noticeable rattling / 'thumps'. However the steering wheel 'play' felt normal and the bearings felt firm. The low speed strong rattle when driving over a rough surface was a good indication that there had to be play somewhere in the steering column.

Cause:
Turns out the upper universal joint on the intermediate steering shaft was loose and had play. Supposedly the u-joints are indestructible, whether it is possible that the bolt has freed himself or whether some previous work in this area has not been carried out properly I cannot say.

Diagnosis:
After disconnecting the lower u-joint on the intermediate steering shaft that sits in the smugglers box I was able to laterally push/pull the intermediate steering shaft and was able to feel some play.

Access:
The upper u-joint sits inside the frunk right before the steering enters the passenger compartement. I was able to access it once part of the temperature / climate controle system sitting on the right behind the break cylinder was suffficiently removed. Pulling off the large paper hoses and removing the two screws from the passenger compartment where enough to push it sufficiently to the side. I was then able to get a clear view onto the u-joint and where it clamps onto the steering shaft to admire the play it exhibited when moving the shaft. I tigthened the bolt and reattached the aircon parts.

Please excuse the bad picture quality but I think you get the idea. In blue the outline where the steering shaft and the upper u-joint sit and the angle from which I was able to access it (arrow) after detaching part of the climate control system (red circle). In the second picture (taken from the web) the lower u-joint and bolt is shown (the one sitting in the smugglers box). The one that came loose on the upper end looks and works exactly the same.

Post mortem:
Would this bolt be able to loosen itself? Would the clamp have been able to gain enough play to actually turn freely at some point (urgh)?

[Uwon]

^^^All the shafts and universal joints are splined to each other and the tightening bolts go thru a slot in the shafts preventing inadvertent slip out or turning on itself. The locking bolts should be accompanied with proper washers an lock nuts.
Johan