Weird brake warning

[Jasonn]

Afternoon all,

Bit of a weird one.

Got in the car, red ramp light and brake pads "worn" no prewarning (yellow ramp) - looking through the spokes, loads of wear left, looked on idrive/service indicator around 7k miles left on the front, 30k on the rears. Stopped car and went indoors for a browse on the Internet to see if its a known problem, got back in car and all normal, warning gone no exclamation mark.

Next morning, it did it again, so squeezed the sensor block connectors under the bonnet, all nice and tight, started car all clear again. Went out earlier and its done it again, had a new battery fitted and coded just before Christmas (it's my daily so doesn't sit around for any time).

Has anyone got any ideas?

 

[Pondrew]

It could be that your front pads are low enough for the wear sensor to be intermittently touching the disc, so making a circuit and showing the lights up.
The way the sensor is located in the cut-out groove on the pad is not exactly 'high precision' and they can move around a bit.

 

[Jasonn]

Cheers Pondrew, I'll see if my local indy can stick it on the ramp (he's pretty decent like that)

 

[Jasonn]

Interesting... Nothing unusual under the car but decided to follow the sensor cables the black plastic clip that holds both of the connectors to a bracket near the suspension strut was more than a little loose - I've bodged it with a bit of gaffer tape and (so far) I haven't had the warning light come on again - it it stays off for the next week I'll do a more permanent fix

 

[Jasonn]

It could be that your front pads are low enough for the wear sensor to be intermittently touching the disc, so making a circuit and showing the lights up.
The way the sensor is located in the cut-out groove on the pad is not exactly 'high precision' and they can move around a bit.

My error - it's the back brakes showing 6k left with 30k on the front.

Gave the back sensor a wiggle but seems solid driving home hit another f*king pothole and it came on after parking up - think it'll be worth changing them out now

 

[Jasonn]

OK - now I'm getting the warning on the front brakes, loads of meat on them - last month the I drive said I had 34k miles left, now 500 back brakes say 5k left.

I'm convinced these f**king potholes are knackering the sensors

 

[Pondrew]

OK - now I'm getting the warning on the front brakes, loads of meat on them - last month the I drive said I had 34k miles left, now 500 back brakes say 5k left.

I'm convinced these f**king potholes are knackering the sensors

The sensors are not linked to the i-drive, apart from when they 'trigger'.
The i-Drive miles to change figures are preset in the computer and then it monitors the number of wheel rotations, to start counting down. It can't tell how you use your brakes, so is a 'generic' estimate.
The sensors are a piece of metal surrounded in a plastic shroud. When the pads wear down to where the sensor is, the plastic is worn off by the disc and then exposes the metal which touches the steel disc. This creates a 'dead short' in the sensor and puts the light on and overrides the i-Drive distance estimate.
Disconnecting the sensors, or even cutting them off and terminating the two wires in a small terminal block will stop the light, permanently.
Sensors are designed as a 'last line of defence', installed for people who never check their brake pads for wear and rely on the 'estimate' of the computer.

 

[Nictrix]

From what I have seen brake pad sensors are all set wrong and trigger far too early, often with more than half of the pad material left.
What this means though is that people who cannot check the brakes themselves rely on garages once the sensor has triggered and the garage will change out the pads. More money for the garages, instead of one set of pad changes per x miles they get two.

 

[Jasonn]

I'm a bit retentive on brakes, I give them a visual check every couple of weeks rather than rely on any sensors.

Had a TR7 and went down to the metal on the fronts once - now I check my brakes regularly

 

[Jasonn]

Update, I had the sensors swapped out a couple of weeks ago - touch wood it's all been good since, so it must've been a dodgy sensor

 

[B21]

Update, I had the sensors swapped out a couple of weeks ago - touch wood it's all been good since, so it must've been a dodgy sensor

Good to know so many times these systems cry wolf..

 

[flybobbie]

I'm a bit retentive on brakes, I give them a visual check every couple of weeks rather than rely on any sensors.

Had a TR7 and went down to the metal on the fronts once - now I check my brakes regularly

Brakes on my TR7 were dreadful, surprised you wore them out.

 

[Jasonn]

Update, I had the sensors swapped out a couple of weeks ago - touch wood it's all been good since, so it must've been a dodgy sensor

Good to know so many times these systems cry wolf..

That's why I posted, just in case anyone else experiences the same - I don't trust the electronic thingymajiggs

 

[Jasonn]

I'm a bit retentive on brakes, I give them a visual check every couple of weeks rather than rely on any sensors.

Had a TR7 and went down to the metal on the fronts once - now I check my brakes regularly

Brakes on my TR7 were dreadful, surprised you wore them out.

It's a skill I possess - managed to kill the diff on the TR as well

 

[B21]

Update, I had the sensors swapped out a couple of weeks ago - touch wood it's all been good since, so it must've been a dodgy sensor

Good to know so many times these systems cry wolf..

That's why I posted, just in case anyone else experiences the same - I don't trust the electronic thingymajiggs

I guess the good news is that providing you don’t skimp and fit fresh sensors each time you change the pads and reset the mileage / time counters it’s likely to save you from scored discs …

 

[Pondrew]

Of course if you just tie the sensors to the shocks out of the way, they will never be a problem and will last eternity. :wink: