Does ls460 have rear brake pad wear sensors?

[donkmeister]

Just failed an MOT for the rear brake pads being under 1.5mm remaining 😲 

Putting aside that ideally I'd have taken the wheels off to check before taking it in, I'm surprised they have got that low. Do LS460s have brake pad wear sensors? Is there a trait for uneven pad wear that means the pad on one side of a rear disc wears down more quickly?

[donkmeister]

Also, how long do you find discs and pads last on these? I've just checked the service record on Lexus link and had new pads and discs all round 7,000 miles ago. Mixed city and motorway.

[Spock66]

24 minutes ago, donkmeister said:

I've just checked the service record on Lexus link and had new pads and discs all round 7,000 miles ago.

I think highly unlikely rear disc pads would wear this quickly, so either there is a fault causing them to bind, or more likely they were not replaced 7,000 miles ago.

I don't have an LS460 but have had other large real wheel driven cars where rear pads have typically lasted 30-40k.

[donkmeister]

Seems likely - I've had similarly big powerful cars and had similar 30-40k miles from rear pads. In fact, I'm pretty sure my old Mercedes did 50k miles on a set of rears before I changed them due to age. 

I don't think the garage was trying it on but I'll order the parts ready to go... In the dark all I was able to ascertain is that the discs definitely have a notable amount of lippage so on that basis it seems likely they need doing. If I can't get new drift pins I'll clean the old ones up and lubricate the sliders with red grease while I'm in there... Hopefully (?!) the previous owner just got ripped off 7,000 miles ago, but I can't fathom a main dealer doing that, it's on Lexus Link rather than a paper invoice that anyone could have knocked up. 

[Spock66]

11 hours ago, donkmeister said:

Hopefully (?!) the previous owner just got ripped off 7,000 miles ago, but I can't fathom a main dealer doing that, it's on Lexus Link rather than a paper invoice that anyone could have knocked up. 

Could just be a typo from the admin person who updated Lexus Link and only the fronts were done, I doubt a main dealer would pull a scam like that (I would hope not anyway).

[donkmeister]

Update on this...

Turns out the calipers had seized and the outboard pads had barely worn. On the nearside the seize is slight, so inboard pad still had plenty of meat on the offside but on the nearside it was barely legal. Discs were clearly replaced at the same time as the pads, judging by the outboard sides. So, I think what happened was the brakes WERE serviced 7,000 miles ago, but the calipers should have been overhauled/replaced at the same time. Entirely possible the previous owner was told this too. 

As I need it back on the road I've ordered a pair of new calipers plus the fittings. I may rebuild the old ones for a side project at some point!

A word of advice to all self-spannering LS460 owners out there; change the caliper mounting screws whenever you refit the calipers. On mine, they had corroded into the calipers. One of them was so badly galled that it required an impact wrench to remove and the caliper will need an insert or weld-fill/drill/tap if it is to be used again. According to some of the US forums, you are supposed to change these bolts every time you refit the calipers, from what I've seen I'm going to say I support that recommendation so factor these in to any disc replacements you do. The part number is 91552-L1245, you need two per caliper (same part front and back) and they're only about £3.50 each (through Lexus). It's a 60mm M12, 1.25mm pitch flange head high-tensile screw, those just don't seem to be available off the shelf!

And a tip: if you need to get an impact in to undo the top caliper mounting screw, remove the plastic aero "spat" that sits underneath the suspension. There are 3 10mm nuts holding it on. Remove that and you can slide the impact up from underneath and attack it square-on. 

Also I have the answer to my original question: there is a brake-pad wear sensor on the offside, but not on the nearside. This sits on the inboard pad and appears to be a broken wire sensor, triggered when you're down to 3-4mm of material left on the pad. 

[donkmeister]

Also I have learned it's not possible to get a proper look at the pads and discs in the dark through the wheel. 🤣

[Malc1]

1 hour ago, donkmeister said:

Turns out the calipers

 methinks servicing the calipers is NEVER on the formal  " to do "  sheet ..... one has to ask for them to be serviced specifically .....  it's poor for the servicing people not to service them regularly but there we are .....  it's built in obsolesence 

Touch wood, ........ my calipers are originals from 242k miles and 27 years of proper servicing 

There's no mention of new calipers on any of the service records I have .........  from new 

Malc

 

[donkmeister]

2 hours ago, Malc1 said:

 methinks servicing the calipers is NEVER on the formal  " to do "  sheet ..... one has to ask for them to be serviced specifically .....  it's poor for the servicing people not to service them regularly but there we are .....  it's built in obsolesence 

Touch wood, ........ my calipers are originals from 242k miles and 27 years of proper servicing 

There's no mention of new calipers on any of the service records I have .........  from new 

Malc

 

I hope you realise you've just jinxed yourself... Buy a full caliper rebuild kit now, to break the curse! 😁

I've had a few seized calipers in my time, but only ever discovered them the first time I replace the brake pads after taking ownership of a car. So I don't know if it's something that comes on gradually and can be anticipated ("that piston was a little stickier than the rest... I really must rebuild the calipers on that axle in the next year or two") or if it's something that you cannot spot until it's happened. I do know that just because a mechanic says "you really need to do this work" doesn't mean a customer agrees to that work though, so I'll withhold from blaming them.

If it wasn't the family transport I'd be happy to buy in a rebuild kit and do it "soon" however currently we're having to use the Citroen Picasso for family duties... a perfectly acceptable car but ours smells of wet dog (mostly because we use it when we need to transport a wet dog). 

[BigBoomer]

The problem with brake calipers is that nobody ever cleans or services them on cars and they are one of the most exposed parts of your car.
On my motorcycles the calipers are highly visible and accessible so I clean them whenever I replace the pads and at least every other year.

What you need to do is to remove the pads and calipers. Then clean the whole caliper paying special attention to the pistons and seals.
First you need to push the pistons out slightly from where they were to give yourself access to them.
WD40 and a toothbrush are great for dislodging crud and dried grease.
If you can get underneath the dust seals then hose it out with brake cleaner and then spray a little lithium grease in there to prevent corrosion.
Once all clean and lubed, refit the dust seals, push the pistons back in, and refit with the new pads.

If you get a dealer or brake centre to replace your pads/disks then they will never clean/service the calipers, at least none of those I have ever used have done so.

[Spock66]

I suspect as the brake pads wear more of the piston is exposed to the elements and corrodes, gets covered in brake dust, muck etc. New pads fitted and piston is pushed back in to accommodate the thicker pads and hey presto is now stuck.

[donkmeister]

1 hour ago, Spock66 said:

I suspect as the brake pads wear more of the piston is exposed to the elements and corrodes, gets covered in brake dust, muck etc. New pads fitted and piston is pushed back in to accommodate the thicker pads and hey presto is now stuck.

That makes sense, thinking about it. The boot SHOULD stop it, but in reality it's only going to stop 99% of rubbish getting in rather than 100%.

[BigBoomer]

2 hours ago, Spock66 said:

I suspect as the brake pads wear more of the piston is exposed to the elements and corrodes, gets covered in brake dust, muck etc. New pads fitted and piston is pushed back in to accommodate the thicker pads and hey presto is now stuck.

Which is exactly why you should clean out under the dust seal and add fresh grease BEFORE pushing the pistons back in.
The grease prevents the corrosion and holds the dirt that gets past the dust seal in suspension.