That Nagging Clunk

reprint of an original ca. 1993, R. Kwas, revised

Generally, I find myself praising the virtues of high materials and engineering quality every time someone asks me why I drive an ancient Volvo(s).  I guess there are the additional reasons of wanting to drive something with some timeless lines (true style always stands the test of time!), "personality", and the personal security of being able to repair just about any failure that might occur myself (if any occur at all), as opposed to calling for a tow and then arranging for a loaner with the dealer.  

It's this same ability to resolve most problems that also makes you and your passengers wonder why you can't locate and repair a certain nagging front-end clunk in that car you're supposed to be in such tune with!  After having replaced all of the suspension bushings, shocks, upgraded to ipd front and rear anti-sway bars, I was truly at a loss for an explanation why every road bump was accompanied by a sound of (it seemed like anyway...) something major in the front-end  wanting to leave the company of the rest of the car.

Then, as the departure date for a Hartford-Chicago trip came near, my eyes were opened when one of the front anti-sway bar mounts ripped out of the frame as I was slowly (honest) crossing the apron of a gas station.  The "saddle-bracket" was of a tab and single bolt (early) style, whereby the tab would reside in a hole in the frame, hooking behind it,  and the lone bolt would hold everything in place (Figure 1).  This arrangement may have taken half as long to install at the time of manufacture, and may seem fine under steady state conditions, but is clearly not up to the task over the long haul or considered dynamically, since pounding caused by movement of the tab, is virtually guaranteed as the bushing flexes during suspension loading.  Particularly, during one-sided suspension excursions such as cornering or bump, when the two ends of the bar move in opposite direction causing torsional flex of the bar.  On the up going side, the mounting bushing is compressed, this results in momentary loss of contact between the tab and frame.  As the tab makes contact again after the excursion, the resulting strike permeates the hole car!  After about a zillion of these whacks, the tab and hole in the frame fatigue ala British Comet aircraft of the '60, and allow the tab to tear out (Figure 2)...luckily the Volvo doesn't fall out of the sky.  Once this occurred, the source of the clunk immediately became clear.  

Quickly, I designed a permanent repair and scheduled an appointment at my local welder two days before the trip...but apparently my little fix-it job didn't represent enough of a potential profit, so that when the time came, they were "busy", which left me with a ripped apart suspension and pissed.  I guess I wouldn't consider then for my next big job either!  The pre-trip repair would consist of bending the tab back into shape and reassembling the mount with neoprene covering the tab as a clunk preventative (I wondered how long that would last...maybe Pennsylvania).  Apparently, I avoided all of I-80's craters on the trip out because happily, the trip went without incident.  I felt like Irv Gordon for a day!  However, while out in the Chicago area (kinda reminded me of Florida with a gridwork of roads, but without the 3PM downpour - please excuse the oversimplification), I did manage to find a crater on a cloverleaf during a local excursion, and ripped the whole mess apart again.  Great!  Car problems 900 miles from home give me excess stomach acid...but a search of the yellow pages found (no kidding) Burner Welding in the area, and Tom over there had time right then, no appointment necessary.  

The fix that he suggested and implemented (Figure 3) is apparently a common fabricator's trick used to locate a captive nut into a blind (backside inaccessible) bulkhead.  After modifying the saddle bracket to make it essentially a two bolt type, locating and welding the captive nut into place, the now upgraded anti-swaybar mounts (similar to later 122s...I guess Volvo figured it out too) were bolted in place - naturally with a dab of tinman.

An hour, $40 plus a $5 tip for cool ones (helps with the welding fumes and dust!) later, the first 50 feet of driving without that nagging clunk was sort of the automotive equivalent of the first morning after a new firm mattress and next to when I first installed those wonderful ipd bars, quite possibly one of the most memorable moments in my motoring career!

In looking back at this episode, whenever a Volvo develops a problem, it almost always communicates this to us...in this case with a clunk.  It is up to us to perceive  and interpret these communications.  That clunk was the clue...I just couldn't figure out which part was communicating and a failure finally resulted.  This communication is strangely absent on British cars.  Hence, at one moment we might be happily motoring along, the next, looking for a place to safely pull over after something crumbles without warning.  I'll stick to the Swedish way, thank you...sometimes I talk back. 

 

Sorry, but this is an old drawing made before I semi-retired my pencil.

 
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