Help: pads stuck to discs after storage
Discussion
My '98 elise has been in the garage for that last few months and I left the handbrake on which was obviously a mistake as the rear pads have stuck.
They're not fully stuck as I can push the car back and forth but it makes a scraping noise if I do that. So I guess the question is how can I spring the pads back into place without calling out the AA! The discs and pads are the original MMC types if it matters...
They're not fully stuck as I can push the car back and forth but it makes a scraping noise if I do that. So I guess the question is how can I spring the pads back into place without calling out the AA! The discs and pads are the original MMC types if it matters...
If you can push the car back and forth, it is not the pads that have stuck to the discs - obviously the discs are moving relative to the pads as you move the car - it is more likely that the calipers have siezed on.
You will need to remove the pads from the caliper (which may take a little gentle persuasion), then free off the caliper. If it is the handbrake linkage that has siezed, this can probably be done by simply working the parking brake lever on the caliper back and forth a few times on either side, to ensure that it is moving freely (using a brake cleaning spray, available from motor factors, may help, but avoid getting it on the discs if you can).
If the caliper piston itself has stuck, you may need to free that off - I usually get an assistant to gently pump it out a bit (not too far, or the whole piston will pop out of the caliper!) by pressing on the brake pedal while I'm at the caliper, then gently lever the piston back in (either using a proper retractor tool or *very carefully* using a long screwdriver or similar. Repeating this a few times will usually free off the piston quite acceptably.
If any of the above doesn't make sense and/or if you don't have a copy of the workshop manual or don't feel comfortable workling on braking systems, give me a shout and I'll try and sort out more detailed info.
You will need to remove the pads from the caliper (which may take a little gentle persuasion), then free off the caliper. If it is the handbrake linkage that has siezed, this can probably be done by simply working the parking brake lever on the caliper back and forth a few times on either side, to ensure that it is moving freely (using a brake cleaning spray, available from motor factors, may help, but avoid getting it on the discs if you can).
If the caliper piston itself has stuck, you may need to free that off - I usually get an assistant to gently pump it out a bit (not too far, or the whole piston will pop out of the caliper!) by pressing on the brake pedal while I'm at the caliper, then gently lever the piston back in (either using a proper retractor tool or *very carefully* using a long screwdriver or similar. Repeating this a few times will usually free off the piston quite acceptably.
If any of the above doesn't make sense and/or if you don't have a copy of the workshop manual or don't feel comfortable workling on braking systems, give me a shout and I'll try and sort out more detailed info.
If you can push the car by hand, the brakes aren't stuck on. Is it just the scraping noise which is worrying you? Do the brakes actually work (handbrake and footbrake)? A scraping noise is most likely just the pads touching the discs combined with surface corrosion, which will go away in normal use as the surface of the disc is cleaned up and the pads are knocked back. As long as the car rolls freely and the brakes stop the car properly, I would be inclined to take the car for a gentle short trip round the block and see whether this cures the problem.
Unless you are confident of your mechanical abilities I would strongly discourage you from dismantling the brakes to investigate the problem. You can easily do more harm than good, you are unlikely to spot the problem unless you know what you are looking for, and even the slightest mistake in reassembling things could be disasterous.
Unless you are confident of your mechanical abilities I would strongly discourage you from dismantling the brakes to investigate the problem. You can easily do more harm than good, you are unlikely to spot the problem unless you know what you are looking for, and even the slightest mistake in reassembling things could be disasterous.
The handbrake and footbrake work, i.e. they make the rear pads grip harder. But the rear pads are definitely lightly in contact with the discs when the brake controls are released.
I can see 1 or 2mm of space between the front pads and the discs that is not present at the rear. If it's safe to give it a spin around the block then I'll do that, but I don't want to do expensive damage to the calipers or discs in the process.
I can see 1 or 2mm of space between the front pads and the discs that is not present at the rear. If it's safe to give it a spin around the block then I'll do that, but I don't want to do expensive damage to the calipers or discs in the process.
1mm or 2mm of space? That's scary, they should be lightly touching in normal use. With that much gap you're going to have to pump the pedal before the brakes work. From the symptoms you've described I don't think there's anything wrong with the rear brakes but its your neck on the line so you're right to be cautious. The main thing to ensure before you drive the car at all is that it stops when you press the brake pedal. Given that, I think what you're describing is perfectly normal.
Just a quick check that might save some time and money, i had a stone jump up behind a metal plate thats angled into the front disc(presumably to guide air flow)and was rubbing on the disc and making a grinding sound. After much panicing i just pushed the plate towards the rad and the offending bugger of a stone dropped out...problem solved.
Hope it that easy 4 u
Hope it that easy 4 u
). It seemed to be just corrosion on the disks and after a bit of a spin it was fine. Obviously excercise a bit of caution to start with!
foxbat said:
I can see 1 or 2mm of space between the front pads and the discs that is not present at the rear. If it's safe to give it a spin around the block then I'll do that, but I don't want to do expensive damage to the calipers or discs in the process.
With respect, the 1-2mm gap you see cannot be between the disk and pad othereise your brakes would not work at all.
Almost all Disk brake systems have the pad(s) in contact with the disk at all times, there is no pad retraction mechanism, the Elise brakes are no exception to this.
You are hearing the pads moving over surface corrosion of the disks and this is quite normal if the car has been unused.
Drive it and the noise will likely disappear depending on how bad the corrosion is.
It's also very, very unlikely that any of the calipers are seized . . . it can happen but usually only does so when the caliper dust/moisture seals are damaged . . . and thus has nothing to do with the car being laid up . . .
Fd
fergusd said:
You are hearing the pads moving over surface corrosion of the disks and this is quite normal if the car has been unused.
Drive it and the noise will likely disappear depending on how bad the corrosion is.
It's also very, very unlikely that any of the calipers are seized . . . it can happen but usually only does so when the caliper dust/moisture seals are damaged . . . and thus has nothing to do with the car being laid up . . .
Fd
Only problem is, the thread started with the statement that that the discs were MMC. MMC discs do not rust, therefore the normal noise from pads rubbing on surface rust on a car which has been standing should not exist.
My Elise (also MMC discs)lives outside and sometimes stands 2-3 weeks in lousy weather: I've never heard any noise of this type or seen any noticeable surface corrosion.
I agree it is unlikely that the calipers have seized unless there is an underlying fault, but it is conceivable that some part of the handbrake linkage or cable has seized.
The other critical factor is how easy it is to push the car - if you can move it without busting a bloodvessel, it's probably OK to give it a run to see if the noise clears, though it is worth checking for trapped stones first.
All this is very well for those of us who are familiar with working on braking systems, but if you've no experience to judge whether there is a fault (or how bad it is), it's probably as well to get the car checked by an expert.
I once accidentally mal-adjusted the handbrake calipers on an Alfa-engined kit car I owned, so that the handbrake was binding on slightly, only to find the brake pedal went to the floor when I tried to slow for a sharp bend 'cos the heat from the binding brake had boiled the fluid. Not that I'd want to worry you or anything...
Wow, thanks for all the advice and sharing some of your experiences. First off I was wrong about the 1-2mm gap, I was looking at the wrong part of the pad assembly. The pads are indeed flush against the discs. Second, there is no rust as they are MMC.
It is really easy to move the car, you can just grasp a couple of alloy spokes, turn and the car will move with ease. I took her for a light spin (boy was it good to be back out in her again!) and there was no problem with braking, everything seemed normal.
I wish I knew where that scraping noise was coming from, now it seems to come from every wheel. Are your cars silent when you push them back and forth? Anyway it doesn't seem to be serious so maybe I'll ask the garage to take a look when she goes in for a service next month.
Martin, last year I had the brake fluid boil on an Astra I was driving on the J8 exit slip road on the M25. First time I found I had no brakes was about 200m from the roundabout at 60mph. I don't know why or how, but I recalled my Dad telling me to pump the pedal if I were to lose pressure. It worked, I stopped, just.
>> Edited by foxbat on Tuesday 10th February 22:10
>> Edited by foxbat on Tuesday 10th February 22:11
It is really easy to move the car, you can just grasp a couple of alloy spokes, turn and the car will move with ease. I took her for a light spin (boy was it good to be back out in her again!) and there was no problem with braking, everything seemed normal.
I wish I knew where that scraping noise was coming from, now it seems to come from every wheel. Are your cars silent when you push them back and forth? Anyway it doesn't seem to be serious so maybe I'll ask the garage to take a look when she goes in for a service next month.
Martin, last year I had the brake fluid boil on an Astra I was driving on the J8 exit slip road on the M25. First time I found I had no brakes was about 200m from the roundabout at 60mph. I don't know why or how, but I recalled my Dad telling me to pump the pedal if I were to lose pressure. It worked, I stopped, just.
>> Edited by foxbat on Tuesday 10th February 22:10
>> Edited by foxbat on Tuesday 10th February 22:11
almost certainly nothing to worry about. MMCs do get surface corrosion despite what people say.
If you keep having the problem (after a couple of hunderd miles), simply remove each wheel in turn, remove the pads, retract each piston (press them in on the front and wind them in on the rears) and then pump them back out. This will probably solve it.
Do check the splash guards on the front and thatthe handbrake mech is realeasing properly.
regards
If you keep having the problem (after a couple of hunderd miles), simply remove each wheel in turn, remove the pads, retract each piston (press them in on the front and wind them in on the rears) and then pump them back out. This will probably solve it.
Do check the splash guards on the front and thatthe handbrake mech is realeasing properly.
regards
greenv8s said:
If you were looking at the back plate rather than the pads, that suggests you only have 1-2mm of pad material left. That isn't enough, and you should normally replace the pads before they get this low.
It could even be that the noise you are hearing is due to worn pads. If they wear right down so that the backing plate comes into contact with the disc, they will make the most atrocious grinding noise imaginable!
If they have worn that low, however, it indicates serious abuse/lack of servicing, in which case I'd get the whole car checked over by an expert if I were you.
If you do need to get new pads, make sure you get the right sort - apparently even some main dealers have sold the wrong type and pads for the MMC discs are getting a bit thin on the ground.
As AromaT said, MMC discs do get some surface oxidisation (very fine, dull grey colour - nothing like as coarse as rust on ferrous discs). I can't see it making much noise, but I didn't appreciate that we were talking about a noise when you simply pushed the car, engine off.
You will be able to hear the pads rubbing on the discs even if there is no corrosion at all if you push the car by hand. As has been said, the pads should be in light contact with the discs at all times, anyway. If the sound is how you would imagine a brillo pad being touched lightly against a rotating metal disc, don't worry about it - perfectly normal.
If it is a grinding noise audible even with the engine running and at moderate road speeds (something like a tool being held against a bench grinder), *then* you may have a problem!
>> Edited by Martin_S on Wednesday 11th February 19:46
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