Mk 1 Avensis ABS brake problem

[talldave]

Hi all - I'm hoping some of the Mk1 Avensis gurus are still around...

I have an intermittant problem on my 1998 1.8 Auto (189,000 miles). When braking at very low speed (e.g. parking or stopping at a junction) I get what I can only describe as a groaning noise which seems to come from the front brakes. I also get feedback through the brake pedal which feels like the ABS is kicking in (a sort or metallic grating feeling) that I have had in the past when the ABS really has come on correctly (e.g. due to ice).

The problem only started after I had new front (Continental) tyres fitted in November - but this may be co-incidence. The problem was worse before Christmas in the cold/icy weather but still happens now and again - even on roads where there is no ice/mud etc. When breaking at higher speeds there is no problem. There are no warning lights on the dashboard.

I'm wondering in the ABS wheel sensor is faulty and telling the ABS control unit to apply the brakes when it isn't necessary?

Any ideas? Thanks in advance.

Dave.

[Stivino]

I’ve seen that, the problem was a split reluctor.

 I’m not saying that is definitively what it is, but it is worth checking.

 

[Konrad C]

When I had my '98 Mk1 1.8 GLS manual, my car had the groaning noise at low speed braking. It happened when almost to stop. It was down to brake dust. The solution was clean the brakes or change the brake pads and/or discs. The cleaning worked for a while, but changing the brake pads worked. I could have used emery paper to clean the pads of any grit.

Strangely one of my bicycles I used during the cold snowy weather, has disc brakes that became noisy due to the muck and grit. I had to use brake cleaner to help reduce the noise. Weeks later they still have the odd noise after the first brake application, then stay quiet afterwards. This is a similar problem to above, so a quick rub of the pads might solve the issue.

If the ABS has an issue, the ABS warning symbol will light up. If not still check the reluctor ring on the drive shafts. make sure muck is cleared from the axle and brakes, as mentioned before.  

[DerekHa]

Hi Dave,

As  Stevino has suggested this sounds similar to a broken or faulty reluctor ring.

My son had exactly the same sort of issue on his old Mazda 323f. The car would drive and brake ok most of the time but he would get similar symptons to yours when he was in slow traffic and then having to brake resulting in that horrible graunching sound you get when the ABS kicks in. Turned out one of the rear reluctor rings had split and looked very like the image Stevino has posted.

[talldave]

Thanks everyone. I'll have a look at the reluctor rings at the weekend.

[avensis_2018]

greate send some pics.

take care.

[talldave]

I had a look at both front reluctor rings today. I just took off the wheels and looked via the access slot - see photo which is quite zoomed in. Both front ones looked like this all the way around, i.e. in reasonable condition and not really rusty or dirty and no cracks or splits. I rotated the wheels all the way around to look at every part of the ring. I didn't look at the rear ones as they aren't visible by just removing the wheels - and I didn't want to take the drum off.

So now I'm not sure what to do next. I could get my local trusted garage to have a look but I don't want to spend a lot getting them to do an investigation which comes up with nothing. Same applies to getting them to remove/clean/replace the 4 wheel sensors. Any suggestions?

When the noise happens (which is not very often, certainly not every time I drive it) it seems to come from the front. Is this because that's where the ABS unit is (in the engine bay) - or does it suggest that the problem is with one of the front wheels? I just want to to try and narrow down where the problem.

Thanks again all.

Dave.

[Konrad C]

On 1/7/2023 at 5:41 PM, talldave said:

I had a look at both front reluctor rings today. I just took off the wheels and looked via the access slot - see photo which is quite zoomed in. Both front ones looked like this all the way around, i.e. in reasonable condition and not really rusty or dirty and no cracks or splits. I rotated the wheels all the way around to look at every part of the ring. I didn't look at the rear ones as they aren't visible by just removing the wheels - and I didn't want to take the drum off.

So now I'm not sure what to do next. I could get my local trusted garage to have a look but I don't want to spend a lot getting them to do an investigation which comes up with nothing. Same applies to getting them to remove/clean/replace the 4 wheel sensors. Any suggestions?

When the noise happens (which is not very often, certainly not every time I drive it) it seems to come from the front. Is this because that's where the ABS unit is (in the engine bay) - or does it suggest that the problem is with one of the front wheels? I just want to to try and narrow down where the problem.

Thanks again all.

Dave.

Looking at the photo, my theory of cleaning the brakes to remove brake dust from the callipers, discs and pads still stands. Wire brush the brake pad mounting points on the calliper bracket and clean the fixing kit. Also wire brush the calliper sand paper or emery cloth and brake cleaner for the discs and pads. Once everything is clean, add copper grease on the back of the brake pads where the piston and calliper are in contact.

If after all the above does not work, then replace the discs and pads. 

 

[Gerg]

I'm definitely not an Avensis guru..., or an ABS one either...

But here are some ramblings anyway:

Assuming that this is an ABS activation noise, so going in a different direction with this to Konrad above, I don't think the ABS system will post an error when this noise occurs - as far as the ABS is concerned it is just doing its job.

When you inspected the ABS reluctor rings on the drive shafts, did you manage to view the end of the ABS sensor itself?  I was wondering if the sensor (which is quite strongly magnetic, no?) had picked up a flake of rust (or maybe had just suffered some general damage) which could weaken/distort the shape of the magnetic field that the sensor relies on to detect motion.

I've never measured this myself, but the strength of the signal from the wheel sensor is presumably related to the wheel speed (not that this is what is being measured by the ECU, that'll be the frequency of the pulses, not the magnitude).  The ABS sensor and reluctor ring is effectively acting as a small AC generator, no?

When the car is slowing right down, if the pulses become too weak to correctly detect (perhaps caused by a piece of rust on the sensor nose?), then the ECU may misread the wheel speed signal and trigger the ABS, perhaps?

It would be interesting to connect a digital voltmeter, on a low AC voltage range, across the ABS wheel sensor's connector (very fiddly indeed without a range of probes to hand - potentially a lot of swearing here), and measure the output from the wheel sensors while trying to turn the hub by hand at a 'repeatable' speed (well, that's any 'science' gone out the window!).  I was thinking that the wheel with the lowest voltage reading could be the problem one that is falsely triggering.  But I wouldn't expect reading this to show a split reluctor ring.

I think slightly more modern ABS systems would more likely detect split reluctors etc.  My 2009 Skoda detected damage to a rear wheel reluctor (corrosion) decisively enough, and would post a fault with the ABS within 50 metres of driving after clearing down the ABS fault code. A reluctor replacement fixed that one.  (The reluctor on that is mounted on the wheel bearing, and is basically smooth with embedded magnetic elements, fwiw.)

A friend's Fiesta of similar age to your car had the same symptoms as yours, this was about seven years back, this dragged on for months.  After a few investigations by the Ford garage (and one from me, too), the ABS sensor was changed by the garage, and the problem went away.

I'm really just posting all this as a basis for discussion, naturally!

Best of luck!

[DerekHa]

Hi Dave,

Agree with Konrad's advice on your problem, cleaning everything up as much as possible could well cure your issue and certainly can't do any harm.

One thing I notice looking at your photo, there appears to be a lot of "mill", the large scaly pieces of rust, that's visible just above the access slot. If any has flaked off and made their way around the reluctor ring they're likely to collect in certain spots and will cause problems with the ABS sensors picking up the signals  produced by the castelations on the reluctor ring. Have had similar problems in the past on different vehicles with the ABS kicking in at low speed and turned out to be rust debris having collected around the reluctor and sensor. Might be more of a task cleaning that out than giving the brakes disc assembley a good clean up though looking at the limited space and access.

[DerekHa]

Seems Gerg is also thinking along the same lines as I am. 👍

Would also add like Gerg I'm not an Avensis owner, now worked on one and also not an ABS guru either. Just applying previous experience and common sense.

[talldave]

Hi again all.

I'm convinced the noise I get (and I only get it when braking at very low speed and then only occasionally) is the ABS kicking in, as I also feel it through the brake pedal.

Thanks for your suggestions. I'm thinking along the same lines as Gerg and DerekHa regarding the ABS sensor(s) being faulty, dirty or having collected debris. However I haven't managed to have a look at them.

I'm going to take the car to my local trusted garage and get them to look at it (the week after next). This may be a bit of a cop out but when I inspected the reluctor rings last weekend I tried the bolts on the wheel sensors to see if I could loosen the. They were pretty tight (no doubt have never been undone before) and I didn't want to break them off so have decided it's wiser to leave this to the garage.

I'll post an update if/when the problem is resolved.

Thanks again for the help.

[DerekHa]

Ho again Dave,

If those bolts won't budge you're taking the right option by getting your trusted mechanic to take a look.

I've had several shear off they were that corroded even after having applied great amounts of WD40 etc. Not easy to rectify a snapped bolt on an ABS sensor!

[Konrad C]

On 1/5/2023 at 10:03 AM, talldave said:

Hi all - I'm hoping some of the Mk1 Avensis gurus are still around...

I have an intermittant problem on my 1998 1.8 Auto (189,000 miles). When braking at very low speed (e.g. parking or stopping at a junction) I get what I can only describe as a groaning noise which seems to come from the front brakes. I also get feedback through the brake pedal which feels like the ABS is kicking in (a sort or metallic grating feeling) that I have had in the past when the ABS really has come on correctly (e.g. due to ice).

The problem only started after I had new front (Continental) tyres fitted in November - but this may be co-incidence. The problem was worse before Christmas in the cold/icy weather but still happens now and again - even on roads where there is no ice/mud etc. When breaking at higher speeds there is no problem. There are no warning lights on the dashboard.

I'm wondering in the ABS wheel sensor is faulty and telling the ABS control unit to apply the brakes when it isn't necessary?

Any ideas? Thanks in advance.

Dave.

In addition to my other replies, when my Mk1 made the loud groaning or bass that sounded like a subwoofer, the worst happened in Sutton Surrey- coincidence! This was well over 15 years ago. When I washed the car, I hosed the brake area of the front wheels and the water came out stained with brake dust. This did help for a while.