'97 406 2 litre Rear Suspension Knock

97 406 2 l rear suspension knocks when running over cateyes or 25 mm sudden
step in pavement. Garage has had no success, but it now has the tightest
set of subframe bolts in the world. Still knocks despite a number of
searches which found nothing untoward. Of course it is difficult to apply
the sort of forces road can apply to the suspension joints.

Any clues?

 

I am not familiar with the set up on a 406 but knocks can be caused by the
strangest things. As an example, I had an Austin 1800 which had a very
nasty knock from the rear suspension over the normal bumps you get in the
road. It was eventually tracked down to the levers that projected through
the brake backplates onto the handbrake cable. Their mounting pins had
worn. The cure was to glue a piece of leather from an old belt onto either
side of each lever where it went through the slot. The repair lasted until
the car was scrapped five years later. The moral is that even silly little
things can sound like something more serious so check everything like
exhaust mountings, mud flaps and anything else underneath.

 

It can be usually 1 of 2 things. The most common is the rear track
control arm. This is the arm that is adjusted for the rear toe-in, one
either side. If you get hold of the wheel at 10 o'clock and 4 o'clock
(on the N/S) or 2 o'clock and 8 o'clock (on the O/S) and push/pull
there should be no play. If there is then they need renewing.
The other thing to check is the anti-roll bar drop link. Not easy to
check, but the wheels need to be on the ground and the drop link
bushes (top and bottom of the link) checked for wear. Really best done
on a ramp.
I'm not saying that there isn't something else, like exhaust, or
whatever, but those two are the most common in my experience.
Good luck!

 

I had a similar thing and my regular non franchised garage gave up. (They
hate Peugeots!)
I took it to a main dealer and they diagnosed it straight away - replaced
both rear anti roll bar links and one front link. It's now fine and no
knocking whatsoever. If I remember it seemed worse going round uneven corners.
Hope this helps.