96 Astra with ABS - Noise on Wheel Rotation

This one has me stumped.

1996 Vauxhall Astra 1.4i fitted with ABS.

The car has started suffering from a slight rubbing noise which can be
heard at low speeds and is speed dependent. It sounds a bit like a
disk pad or drum brake shoe rubbing against a slightly out of true
disk/hub or something rubbing against a wheel or tyre.

The noise can only be heard when in the car (seems to travel through
the bodywork making it difficult to pin down the source) and seems to
be once per wheel revolution. Applying handbrake or footbrake makes no
difference to the noise.

All wheels turn freely when jacked up although the rear offside you
can hear a very slight rub on the shoes once per revolution.

I tried braking the car gently on a downhill stretch of a quiet road
and found that turning the ignition off stopped the noise. Turning the
ignition back on (but not starting the engine) caused the noise to
reappear!

No warning lights on the ABS and no trace of vibration/kickback is
felt through the brake pedal.

ABS warning light comes when turning ignition on & then goes out a few
seconds later just as it should.

Any suggestions gratefully received.

 

Sounds weird.

Until you mentioned ignition, I would have thought (in order)... (a) bit of
grit (or similar) caught; (b) a pad worn down to its rivets; (c) wheel
bearing; (d) CV joint. I guess a damaged tyre is also a possibility, but
wouldn't expect the noise to "travel through the bodywork". Have you looked
closely at anything rubbing against a wheel (eg twig etc) when NOT jacked
up.

I can't imagine what the ignition can be doing, and would be useful to have
more detail re. this "ignition test". Eg was it in gear when you did this,
or neutral? I assume neutral, else engine would surely re-start when you
switched back on.

In any event, it looks like rear offside is first one to check

Don't be offended, but "just in case".... do take care with any tests which
could prevent power assist braking from working, and obviously don't lock
steering by removing key while moving.

 

Thanks for the suggestions Martin - & don't worry, good advice and no
offence taken! On the test I did the other day it made no difference
whether in gear (clutch depressed) or not.

I have cleaned out the rear offside drum and jacked up it then rotated
freely.
I took the car out for a test run. Reversed out of the drive without
touching the brakes and then started driving forwards - no noise until
I had gone a yard or two when an electric motor kicked in for about a
second then stopped. Noise returned immediately that happened - still
without touching brakes. This can be repeated at will without
touching the brakes by allowing the car to roll to a halt, turning off
ignition then restarting the engine. Shortly after the car starts
moving the electric motor runs for a second and the noise starts.

Whle I had the rear offside wheel off I could see no obvious sign of
rubbing on the tyre or wheel bit there was a small polished area on
the fuel filler hose near the tyre. Not sure if I did it removing the
wheel but I am now wondering if that hose swells when the fuel pump
pressurises the system but I would have thought that would occur
straight away when turning the ignition on.

It must be something rubbing as the noise stops when going round a
left or right hand sharp bend.

 

Thanks for the suggestions Martin - & don't worry, good advice and no
offence taken! On the test I did the other day it made no difference
whether in gear (clutch depressed) or not.

I have cleaned out the rear offside drum and jacked up it then rotated
freely.
I took the car out for a test run. Reversed out of the drive without
touching the brakes and then started driving forwards - no noise until
I had gone a yard or two when an electric motor kicked in for about a
second then stopped. Noise returned immediately that happened - still
without touching brakes. This can be repeated at will without
touching the brakes by allowing the car to roll to a halt, turning off
ignition then restarting the engine. Shortly after the car starts
moving the electric motor runs for a second and the noise starts.

Whle I had the rear offside wheel off I could see no obvious sign of
rubbing on the tyre or wheel bit there was a small polished area on
the fuel filler hose near the tyre. Not sure if I did it removing the
wheel but I am now wondering if that hose swells when the fuel pump
pressurises the system but I would have thought that would occur
straight away when turning the ignition on.

It must be something rubbing as the noise stops when going round a
left or right hand sharp bend.

-------------------------------------

Sorry kevman - I can't fathom it. I'm surprised that some of the really
experienced folk on this group haven't replied.

In the absence of other posts, I can only suggest you try to get a "free"
diagnosis from your local Vaux shop.

Please post back if you find the answer.

 

Have you tried un plugging the abs pump?

 

The Astra ha just passed it's MOT with no problems reported. The
dealership wanted £50 just to plug their diagnostics in so passed on
that one fo the moment!

I have tried a few more things and the symptoms of the regular rubbing
noise seem to be as folows:-

Drive the car with withthe ABS fuse pulled out - no noise

Set off slowly forwards - initially no noise until wheels have turned
for approx 1 revolution then whirring noise (ABS pump running?) for
about 1 sec followed by noise once per wheel revolution.

Drive the car round a car park & noise seems to stop when turning left
or right, Also stops when going round roundabout.

Noise is the same whether braking or not.

Rolling the car downhill wih either no brakes, footbrake or handbrake
on noise is there. Turning ignition off - noise stops. Ignition back
on (engine not started) noise returns once ABS pump runs for 1 sec.

ABS warning light operates correctly on ignition on and then stays
out.

No trace of ABS vibration through the brake pedal.

Could it be that the noise I am hearing is actually the ABS pump
running regularly? If so, why would it stop when going round corners?

 

The MOT pass isn't a certificate of perfection, it's just a statement of
"good enough". When the ABS does it's initial self test run it probably
brings the pads right up to the disks. I'd look for something not quite
right in wheel bearing/disk area. If there's any play in the bearings
cornering will open up the pad clearance and that may silence things.
I had something similar for a year on my astra and wasn't able to find
it. Fixed by a trade-in