Knocking noise in Astra while driving

Hi all,

For the last few years, there is a 'muffled' irregular knocking noise
in my 1992 Astra while driving straight or turning. It's almost like a
dead-sounding rattle. It is particularily noticible in cold weather on
slightly uneven terrain (such as a bumpy road surface), and at speeds
under 30mph. The noise corresponds with the severity of the bumps. It's
not the engine, because the sound is still there if I free-wheel with
engine switched off. It's not as severe in warm weather either. Over
these years, wear and tear has seen a new exhaust, front shock absorber
mounts and anti-roll bar bushings installed, but the sound perists just
the same. It's very different from the sharper sound from C-V joints,
and anyway, isn't present on smooth terrain while driving straight or
locking the steering. Driver's door was rattling due to worn hinge, but
I fixed this and checked other doors also. Sound seems to come more
from the front. Any ideas on what it might be? Could it be the shock
absorbers? Mechanic couldn't find anything wrong and the car recently
passed MOT with no problems. I'd love to solve this puzzle though.

Thanks,
Brendan.

 

I'd be interested in this - I have the same problem Untraceable by my local
VX dealer who claimed it to be front pads 95% worn (miraculously they were
only half worn hen they looked again a few weeks later), a fractured fan
mounting (it wasn't), a loose fan mounting (it wasn't), worn links (made
little difference), and worm shockers (which I can be forgiven for being a
little sceptical about, given the cost of replacement and the fact that the
same garage passed it through it's MOT about weeks after this one!)

 

long shot, but have a (close) look to see if you have a bit broken off one
of the springs. the last couple of inches can break off with no real effect
on ride height, but will remain in the mount, banging away at will. you
really need to put it up on ramps for this though..

Mike

 

Most probably suspension bushes of some sort (anti-roll bar links?) or
even a mis-aligned exhaust. I had a car where the exhaust would rattle
but only when it was raining.

 

well the short term solution to that is easy-dont go out in the rain <g>

I would be inclined to reject the bush idea though, as the OP said it
recently passed mot.

Mike

 

Hi,

One drop-link and bushing was replaced and the other set checked prior
to MOT which passed. I haven't noticed the effect of rain, but
temperature definitely plays a role. The sound seems much louder when
the weather is cold.

Brendan.

 

I've got exactly the same symptoms on my H reg 1.7 diesel Astra.

It's just developed over the last month or so, and like you say when the
motor really gets warmed up it almost disappears, that is unless I hit some
really bumpy potholes.

I checked it out but couldn't see anything physically wrong, mine has also
recently passed an MoT without any comment on steering or suspension.

Perhaps it's just one of those things that afflicts older Mark 2 Astra's, as
I'm pretty certain that if it was a dangerous or serious problem it would
certainly have been picked up on by now.

I initially switched from a 1987 1.6 petrol estate to a 1990 diesel version,
which apart from performance issues was like driving the same vehicle, as ev
ery problem that afflicted the petrol version was the same on the diesel.
i.e. wallowing suspension on cornering, understeer, woolly gear change,
rattling glove compartment lid, fuel gauge with variably unreliable
readings, screeching blower motor etc.

 

My Carlton has just passed an MoT yet it sounds likes a drum solo
driving over rough ground. There are limits as to what will pass an
MoT and what won't.

If it's temp related then I'd take a guess that it's some rubber
component somewhere on the car

 

don't know if this helps but had a similar problem turned out to be loose
heat shield on the exhaust

 

That one does sound interesting - do you mean the one that you can see as
soon as you open the bonnet, below the spark plugs, or is there another one?

 

I think it was the one by the cat. the mechanic got under the car with a
screw and screwdiver in hand anyway and when he came out there was no more
knocking.