W reg 626 During MOT main dealer reported front discs "corroded"
and pads 85% worn.This one year after purchase and full pre-sale
in depth check over, and 5000 miles.Car mileage is 47000 so worn discs I can understand- but corroded?. Any body like to comment
please.
Ed
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Targets to be met with regard to sale of brake discs and pads.
What is "85% worn" anyway? Does he know exactly how thick they were when new, measure them, and carry out a calculation?
I'm sure someone will clarify, but AFAIK the MOT test doesn't require a particular thickness of pad - merely satisfactory performance when tested and no unusual noises indicating metal-to-metal contact? The tester shouldn't even have the wheels off in any case.
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GrahamF1
Yes, 85% is a bit accurate isn't it?
You're right the MOT used to be brake efficiency alone. However, I think the MOT visual check now includes brake pad and disc condition, so badly worn pads or discs can cause a fail. They don't carry out any dismantling, so drum brakes don't get a wear check.
See the MOT testers manual
www.motuk.co.uk/manual_350.htm
sections f, g and h.
JS
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How much can be inspected depends very much on the car concerned, because the wheels should not be removed.
Most alloy wheel and brake caliper designs allow a peek at the outer pad, but the inner one generally remains hidden. Steel wheels and you've not got much chance of seeing anything.
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Graham
Don't disagree, but the option remains for them to fail the car if the limited inspection shows problems.
JS
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I agree with that John, but they must be able to demonstrate the problem(s). They can't fail a car because they think the brakes might be dodgy, but can't get at them to find out without taking the wheel off.
If it passes the efficiency test and they can't see any faults without dismantling, it passes. If it passes the efficiency test but doesn't perform anywhere near the level expected of that model of car, then they can issue an advisory but cannot fail it.
Of course, in practice it doesn't really work like this. They phone you up to tell you there's a problem and when you arrive the car is on the ramp with the wheel off. They've automatically assumed that they'll get the work - by taking the wheel off they've stepped outside the MOT test procedure and are now examining/repairing the vehicle.
In theory, you'd be well within your rights to say "What do you think you're doing? I asked for an MOT test, why is that wheel off?"
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I agree with that John, but they must be able to demonstrate the problem(s). They can't fail a car because they think the brakes might be dodgy, but can't get at them to find out without taking the wheel off. If it passes the efficiency test and they can't see any faults without dismantling, it passes. If it passes the efficiency test but doesn't perform anywhere near the level expected of that model of car, then they can issue an advisory but cannot fail it.
Absolutely, that's how it goes. The MOT only requires 0.5g from the main braking system, which is pretty dismal. They would be right to post an advisory if they were anything like that, but can't fail it.
If you turn up and a wheel is of, then that's difficult. It's strictly at their risk, because it is, exactly as you say, well outside the MOT. Problem depends on if they've passed the car or not. If the car has failed one might suspect suspect it's based on the strip down, but if they've passed it and are looking for work they are being more honest, albeit putting pressure on the customer. How many garages would do this I don't know - I suspect most would not be able to do it there and then , but just say 'the brakes are poor', post an advisory and assume the average punter will be scared enough to give them the job. I have to say I've never had any pressure put on me to have any advisory work done, although any I've had have been small items. Depends on the car too - I doubt they'd expect to get any jobs from me on the Minor which I've virtually rebuilt.
There's no doubt they do exaggerate problems though. I knew the rear tyres on my car were down to about 2.5 to 3mm at the last MOT, but just hadn't had time to get them replaced - I'd done the ringing round for prices, and was getting them done later in the week. Rightly, it passed the MOT with the note that one was down to 'legal minimum' (which it wasn't) but although they sell tyres they didn't even give me a price! Charitably, one could say they are erring on the side of caution, not knowing that I was one of the customers that actually checks tyres regularly.
JS
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Do you know if they should ever have the bonnet open during the MOT? Reason I ask is to clarify in my mind whether I got ripped off by those people who sold me a new battery "bubbling over with acid mate, probably being overcharged".
I assume the exhaust gas analyser connects to the tailpipe(s) - if so I can't see much of a reason for the bonnet to be opened.
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Yep, bonnet always opened on MOT. They have to check the VIN number (if appropriate), they usually look down the back of the engine for PAS leaks, inspect the brake servo and lines, check for corrosion around the suspension turret tops, brake master cylinder mounting points, check the oil temperature before doing the emissions test, I think they check the security of the bonnet catches as well.
You seem to have some very bad experiences with MOTs Graham - I have always found them to be OK - they usually pick up the things I knew about anyway. The battery does sound a bit jubious though - if one battery was being overcharged, no reason why the replacement wouldn't be. I would certainly have demanded a look at it, and washed the acid off afterwards to prevent it rotting half the car away!
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RichardW
Is it illogical? It must be Citroen....
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DIY. Jack up car, support, remove front wheels and get a torch. If there is less than a couple of mm. of pad left, change them. Simple job and costs about £20 per axle. Discs can be corroded without affecting braking provided 'braking' surface is smooth and shiny. If there is a thick section of rust around the outside edge of the disc, have them checked for thickness against manf'rs spec. Details in your handbook. If you don't feel up to checking this, any local mechanic should tackle it for a small payment.
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Should have asked, was this advisory or did he fail car?
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I had a car fail due to 'corroded' disks. (first MOT after buying old Renault 5). I hadn't done any real checks before taking it in, used the MOT as a quick 'whats wrong with it' test.
The disks had aroung 1/2" of thick flaking rust around the outside edge of the disks. This had ground down the pads so that only 1/2 to 3/4 of the pad was on the shiny bit of the disk. Looked terrible.
I put it down to short driving distances and parking outside (and cheap replacement disks). I had the car 5 years and replaced the disks every 18 months for the same reason.
The brakes flew through the brake efficieny test - which is still based on very low standards - except for balance.
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Did this Renault 5 have alloy wheels? I'd be surprised if it did...
So how were they finding all this out without taking the wheels off?
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Did this Renault 5 have alloy wheels? I'd be surprised if it did... So how were they finding all this out without taking the wheels off?
No, Steels. Stood out like a sore thumb on the inside of the disk - easy to see when checking streering linkages.
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I would say 85% worn is a lot.Mot. Failure of pad is 1.5mm.Too low for my liking..should be around 2.5/3mm.Pads do start to break up at or around this level.So taking a pad this low is asking for trouble.If discs are below man/rec thickness they should be replaced.corrosion of disc can be sorted ie section of disc not contacting pads..by scraping of disc where corrosion exists.
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Steve
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Eddie doesn't state that the MoT was failed on these points, just that they were 'reported'. One assumes therefore that the roller test was passed.
However, this was 'reported' for a reason - namely that whilst adequate for the MoT the brakes are in poor order.
For very good technical reasons which have been discussed at length here in the past you should NEVER EVER let your brake pad friction material drop below 3mm thick. Worn, scored or corroded discs also will not perform at peak efficiency and an emergency stop may take several car lengths more than with new discs/pads.
Get new discs and pads fitted AT YOUR EARLIEST CONVENIENCE. Either your or someone elses life may depend on it.
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Cyd.Its a bit of a grey area.Reported on this point can mean its ok to leave untill a problem/dangerous as it is.Can be left.My point was and as you stated..either brake pad or shoes.SHOULD be checked regularly.I forget the amount of motors in the past. I have done MOT checks on and found pads down to well below limit.I think the MOT check should allow for removal of wheels/drums..Plus IMO the motor. ok passed the roller test.Should have failed.Not given as a report..Just my thoughts.I suspect many would dissagree with some points??
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Steve
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Eddie has only done 5k miles in a year. Time for surface corrosion to wear pits in disk surface and destroy pad life. I've seen it happen . I bet Eddie is a gentle driver and does not brake hard when he uses the car? Or washes it weekly and garages it without a run? If so the disks will be put away with surface water and rust. When he drives away it will wear off the rust but the pads will wear very quickly . And the disk outer circumferance will corrode and flake.
My answer. ALways drive car in drive and brake several times before garaging car after washing (prefer to drive further but not always possible). Brake hard at least once /week several times (easy here: a 300ft high hill outside house braking all the way down:-)
Change disks and pads now and adopt a policy as above of hard use omce a week will keep disk surfaces rust free and prevent pitting (if not eventually pads wear unevenly and braking in a straight line becomes difficult/safety isses.).
Do not wash car wheels with proprietary wheel cleaners or water and then leave car disks to rust...drive it!
If you are driving every day 20 miles + per day it's not relevant but 5k miles /year meand rust build up..imo
madf
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madf
your comments generally "spot on" except that I only clean the car
about three times a year, and am careful about wetting discs.
My main dis-satisfaction with the garage was not that the pads and discs needed changing after 47000 miles but that the reason was "corrosion" and that this and the wear had occurred in 12 months and after 5000 miles to discs and pads which had been inspected and mot'd as a pre sale check.
From the logic that low mileage and being parked outside caused this deterioration then one would expect the rear discs to be affected in the same way, and they seem fine.
To those responders (thanks) who commented that the mot does nort include removal of wheels,I should point out that this mot was carried out in conjunction with a main service which includes inspection of discs and pads (plus changing oil,air,fuel filters,
replacing engine and gear box oil, coolant, brake fluid-do they really do all that how do we know? But that's another subject!!!
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The service would have been done before the Mot.And so if the pads/discs were ok.they would not have changed them...But this would also depend on the amount of wear already there.As long as they are within spec it will pass.But may not last as long as you would expect??
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Steve
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