Brake Disc Corrosion - The Extreme Edition...

[Wabbitkilla]

I've not had this problem with the '2 yet, but the Yaris Ts has the same problem, and on the outside surface.

I've never seen corrosion on the swept surface of brake disks, uneven wear because of sticking sliders but never corrosion.

My betting would be;
Poor cooling (made worse by the rear shield)
Poor ventilation not allowing pad dust and gases to escape (that shield again and pad design)
Poor pad composition.

I'd like to know if it's legal to remove the rear guards from the brakes as these cannot be helping the situation - I don't remember seeing anything like these in my pre- Toyota days!

[Anonymous]

This was reported on my 54 plate when they did the 2 year service at 5.5K miles

seems to be a common point of concern on the 2

[Anonymous]

Update:

I finally got around to looking at my brake system to see if I could find a source of the problem with the scored/corroded discs. It looks like my original mutterings about the slider not working were correct, but not in the way I thought...  s:shock: :shock: s:shock:  

When I dismantled my system yesterday I found that the inside pad was very heavily worn and the outside pad had seen very little use (estimate inside pad was 3-4mm remaining and outside was 7-8mm remaining). This proves that the slider on my car is not working properly as forces on the inside and outside of the disc should be equal, hence wear should be equal. Judging by the similarities here I would suggest the same is true for some of you poor souls.  s:( s:(  

What appears to be happening is that the inside pad (pressed directly by the calliper) is making good contact against the disc. However, the outside pad (which is drawn against the disc by a sliding mechanism) is not making very much contact with the disc. This means that nearly all the braking load is taken up by the inside pad. This means that a lot of heat is generated by one side, which increases the rate of corrosion.

The slider itself was quite stiff when I first took it off, but after a little working it became free. The pins that the slider run on are sealed and greased, but this had baked a little and is now more like a paste. I will clean this section up carefully and make sure that there are no rusty bits on the pins (and recess – if possible) before re-greasing. I will also make sure that the whole area is as clean as possible before refitting.

As mentioned the piston in the calliper seems to work ok, but as you might expect it was very stiff due to fact that you are trying to push a relatively thick fluid up very small pipes (I do not have one of the special tools for pushing the piston). I did not get under the boot that protects the piston, but I would like to do so in order to make sure this is clean and running as freely as possible.

Interestingly, BenF makes a good point here about Copperslip. The old remains of copperslip that had been applied to the brake pad sliders was revolting! It bore no resemblance to grease and was actually inhibiting the movement of the pads. This could be adding to the problem. I will try and source a high temperature grease of another type.  s:?: :?: s:?:  

In short, it looks like we need to service these parts regularly. There is nothing there that is particularly scary to work on so it is something you can do with a little bit of knowledge. Further more, I doubt that changing the type of disc or braking material will help with this problem as I'm pretty sure that if the calliper/slider system works properly then this problem will go away.

I'll see how things progress after I've got mine back on the road and will keep you posted.

[1bloke1dog1mr2]

My front discs and pads were changed under warranty at just under 20K miles. This is before I owned the car, but I have noticed a slight knocking on the brakes over the last few weeks. It's like a rythmical thud on the brake pedal which is related to speed so it slows as I slow. There is no nasty noises, the car doesn't pull to the left or right and the steering wheel doesn't vibrate. It does seem to happen more when I am braking harder.
I had my intermediate 5 year/50K service done in March with no reports of problems with discs or pads, the car's done 40k miles now. Is it worth checking them out with my local garage as I have no warranty left now?

[Anonymous]

It's like a rythmical thud on the brake pedal which is related to speed so it slows as I slow. There is no nasty noises, the car doesn't pull to the left or right and the steering wheel doesn't vibrate.

I would say yes, its worth getting them checked.  What you describe is exactly the feeling I was getting from Lynn's car before I changed the disks and pads.  Brake feel was smooth as silk after the change.  Got a nasty feeling the bumpiness is kreeping back now.  Think it may be time for me to have a look at those callipers!!

David

[Anonymous]

I just checked my discs after this subject arose.My car has 120,000 up on it,now I'v only had it since there was 99,000 on it last august but my discs are perfect.Quite possible that the previous owner had them changed but who knows....is it a relatively isolated problem to a handful of cars or a epidemic?

[Anonymous]

Hey guys,

Just a quick update. It's nearly 18 months since I last commented on this topic and I thought I'd bring you up to speed.

The servicing of the calliper/slider system seems to have done the trick. I have now replaced the pads on the front/rear twice since my last post ( l viewtopic.php?f=11&t=11672#p154503 l ) and I can confirm that the scoring/ringing of the internal surface has not come back.

This confirms that the scoring is a symptom rather than the problem itself. If you regularly service your bakes and keep them running smoothly you will achieve equal braking on the inner/outer pad which removes the scoring issue and results in fantastic braking performance!. Seriously, I thought the brakes were good before, but when all four corners are working properly its simply unreal.

Note: One thing I immediately noticed after servicing the slider is how the outer (visible from the road) surface of the disc is visibly brighter/shinier than before. In other words the pad is making contact under braking.

[ChrisGB]

Looks like this is worth doing for me. The outer face is not being swept as effectively as the inner face on both fronts with mine, so will have a go. When I replaced the discs and pads, it all seemed to be sliding reasonably freely though. Anyone got an exploded diagram of the calliper for reference?

Chris

[custardavenger]

I think it may start to be a problem for more members as the cars get older. Mines a 2000 and over 100K and I have the calipers off to paint them. Am really glad I did as they were in need of a good service. I may try and do a "How to" on it.

[ChrisGB]

I think it may start to be a problem for more members as the cars get older. Mines a 2000 and over 100K and I have the calipers off to paint them. Am really glad I did as they were in need of a good service. I may try and do a "How to" on it.

Mine have been having problems since 30,000 miles and less than 2.5 years old. I wonder if using a jet wash on them has any relevance. Certainly can cause issues on some older cars.

Chris

[custardavenger]

I definately wouldn't recomend jet washing the calipers. The rubber seals arn't that good.

[ChrisGB]

I definately wouldn't recomend jet washing the calipers. The rubber seals arn't that good.

I try to avoid it, but previous owners may not have done.

Chris

[BenF]

Just to add my 2p worth - I also had a really bad set abuot 12 months ago ( see also  m http://www.imoc.co.uk/forums/viewtopic.php?t=153178 m  ) and suspect the issue was the sliding pins getting seized up, causing the inner brake pads to do the majority of the work resulting in gazed inner pads.

I fitted new disks and pads, and have tried HT grease, and even not using any grease but both would eventually bind again.

After being on the car for 12 months, I recently checked them and noticed the new pads and disks again had some light scoring on the inner surface and so discarded them and got another set of pattern disks and Mr T pads.

At the same time I looked for a source of 'Lithium Red Grease' or 'Lithium Soap' to use on the sliding pins. Although a little used to be included in brake refurb kits it doesn't tend to be nowadays.

Calling around different local motor factors, I found one selling 'red brake grease' sold in a big ~ 300g tin - something like this from ebay  m http://www.ebay.co.uk/itm/Millers-Oils- ... 0413202450 m  but the one I had was a different brand ( if there's interest, I'll grab a photo tomorrow ). Certainly assembling the caliper again, the grease is different to others I've tried as even with a thin film there's very little resistance to movement - there was a little more 'stiction' with the other greases I've tried.

I've reassembled the brakes, and since done a trackday. The brakes still feel OK now, but I need to take some time to strip down and confirm the red grease is doing the job needed, but at the moment I'm hopeful it has done the job.

[Steve Green]

The thread that refuses to die and resurfaces every three years.

Red grease, or Red Rubber Grease is intended to ease the assembly of rubber components. Its not designed for metal to metal contact. It is designed to be brake fluid compatable.

The biggest problems on calipers is the combination of water, heat, and neglect. The best greases for the sliding pins are lithium based designed to resist water washout.

[BenF]

Steve - ok - where would you get some then? Other online forums suggest lithium spray on grease and similar, but I would have through that was much too thick and would suffer the same fate as Molly and copper slip based greases in that the sliding pins eventually seize up.

[Steve Green]

My prefered option would be

http://www.opieoils.co.uk/p-6315-castrol-moly-grease.aspx

The grease has good water wash and sliding characteristics.

Brakes are a bit of a thing for me, if you look at the How To section.

I like the idea of being able to stop. That means that every couple of years, I strip, clean and lubricate my calipers and do not replace pads without doing a complete checkover and replacing external seals etc.

[BenF]

FWIW, have had exactly the same issue and swapped front disks a number of times on my 2003 car. The root cause I found was sticky sliders as you found.

I've tried most greases for the sliding pin ( White Lithium, Red brake grease, CV grease ) but all of those have baked hard with time / use and the pin seizes up.

What you really need is some silicone grease - very difficult to find the right stuff ( similar comes as part of the Toyota brake caliper refurb kit ) - I found that Bigg Red were selling some via ebay - :

 m http://www.ebay.co.uk/itm/Silicone-grea ... 4171da1bcf m

I bought 6 packets and stripped and re-lubed the sliding pins on the front and rear of my car with some about six weeks back.

Since then, the brakes 'feel' good and are working well but I've not stripped the brakes to confirm the pins are still OK

[Jon_G]

The brake section of the Toyota service documentation states "lithium soap base glycol grease" (I'd upload the pdf file if I could find a way, but happy to email to anyone interested).

Didn't have any when I replaced the front disks about a year ago, so used this instead...   m http://www.ebay.co.uk/itm/CARLUBE-SILIC ... 1501wt_721 m  ... still good when checked a couple of weeks ago.

[Markb]

I'm well pleased with the Mintex Ceratec grease,my other car,the Ford Probe has Mazda brakes,sticking on the sliders is a common problem,they would need stripped and greased yearly if not twice a year......used the Ceratec 3 years ago and i have not had to re grease them yet.The grease stays there,it does not go hard and cause sticking like the old copper slip......also done my Rav4,the Mondeo and the rear of the Mr2.

My original Mondeo front discs were rotted through on the inside at 4 years old.......on the subject of removing the brake disc guards/shields,i asked at the last Rav4 mot as the fronts are a bit rotten,i was told it would fail as they protect the flexi hose from disc heat.....so they can be there and rotten and pass but take them off its a fail,alot of cars dont even have them now,new vauxhalls for one.....got nice new ones from CTP,must fit them sometime  s:lol: :lol: s:lol: