DIY Car Mechanics Explained - Changing Brake Pads & Discs

[Lopéz]

Okay, just a simple guide as it's a regular topic that comes up for discussion - how to save yourself rather a lot of labour charges by doing a simple job like changing discs and pads yourself. You need a jack, axle stands and a basic tool kit. Your caliper may well be held on with a special allen-key style socket. No, a normal allen key will not really do the job, not enough leverage.
A caliper winding tool is also useful, but not essential.

Please not all cars are different and may have different methods for holding the pads in (pins, bars, etc) - but with a little common sense the theory is basically the same.

I accept no responsibility for you damaging yourself or your car, this post is for interest value only!

One car. Jack it up and take off the wheel....

To reveal a truly rogered brake disc. Ignore the rust, that is of no consequence - but check out the scoring on the disc face! Not good. This is what happens if you don't change your pads the moment they begin to get noisy.

So, remove the anti vibration clips (these hold the caliper and slider apart at the right angle)

Then using a power bar, crack off the two nuts (usually allen-head sockets) that hold the caliper to the caliper carrier. These may be VERY tight! Then undo them with a socket. Sometimes both need to come out, sometimes just the top one and then let the caliper swing down. On the Mondeo, both need to come out.

At this stage, pop the lid off the brake fluid reservoir, or you will have a mighty struggle to push the pistons back into the caliper.

 

[Lopéz]

Now get a bar and lever the caliper gently away from the carrier..

Like so. Pop out the pads (they just fall out on most sliding caliper designs) and support the caliper to save damaging the brake hoses.

Well and truly rogered.

Now, peer behind the disc and you can see the carrier (the large metal bracket that goes round the disc) is held in by two big bolts. Undo, and remove the caliper carrier.

Now you are free to remove the disc. Some have a retaining screw which will need removing or drilling out first. On the Mondeo, a hammer comes in handy as they tend to stick onto the hub. I had to belt seven shades out of these before they came off.

 

[Lopéz]

After a lot of frenzied banging (hur hur) the disc should come off. Make sure you clean up the hub thoroughly or you'll get the notorious "warped disc" sensation.

New discs. Shiny shiny, clean them with brake cleaner first as they tend to be covered in an oily film

Refit the carrier..do it up....tight.

Now this is a caliper winding tool. What a brilliant device.

It lets you push the piston back into the caliper relatively easily - a job that otherwise requires herculean effort, a crowbar, and lots of swearing and stuff. When it's wound right back you can put in the new pads.

 

[Lopéz]

Now the caliper is fully rewound, you can place the new pads in both the carrier....

And into the caliper - these are held in with sprung metal clips and can be tricky to get in so use a screwdriver to wedge them in if you're struggling.

Be careful here! Bolt the caliper back to the carrier - it's hard to get them straight on some cars, and I ended up cross threading the bolt, badly damaging both bolt and carrier! I got a whole caliper which I used for parts from a scrappy for £20 - put it down to experience and you'll not make the same mistake again.

After replacing the clips (the ones I removed at the start of the job) you can bolt the wheel back on and remove the car from axle stands. Put the cap back on the brake fluid reservoir (if you've been topping it up, it will now have oozed out everywhere ) and drive gingerly down the road, press the brakes a few times to get the pedal feel back, it may be spongey at first.

Job done! Drive carefully for the first few hundred miles, and avoid hard braking over long periods. Or just follow the pad manufacturers instructions for bedding in.
Hope this was of some use.

 

[Lopéz]

Anyway, my discs are warped and need changing soon, so I might have to borrow that winding tool off Gordon if he'd be so kind

Show him some cleavage and he'll do anything you want.
I have another guide coming soon, will start stickying this sort of thing. If anyone else has pictoral guides that they want to write, or have already made,(for ICE, mechanical stuff, bodywork, GPS installation and so on) then RTM the thread or mail me and we can get them added to the sticky.

 

[Lopéz]

Cheers for the replies, here are the answers to a few points.

Copper grease is great, but I've never ever ever had squeal except on Fiestas so I don't bother with it any more I did use some on the hub but my hands were covered in the stuff and I'd run out of gloves so I was trying to be sparing with the pics before my A80 started looking like it had been subjected to a black/copper respray

Yep, a G clamp is good for pushing the pistons back - they also come in handy to pinch the bottom of a balljoint when the thread keeps turning.

Been using cheap discs for years and never had a problem. Good pads are a wise investment though - these Apec's are cheap but they usually last well so all the local Taxi firms use them.

Pumping the pedal pretty much comes naturally, the brakes were back to normal by the time I'd moved the car off the ramps (I cheated a bit and had the luxury of air tools and a proper workshop, but it's just as easy to do on the driveway.

If anyone wants a decent thread archiving, just use the RTM button (the exclamation mark under the avatar column) so it brings it to our attention.

Glad some people found the thread useful anyway.

 

[Lopéz]

One thing, if the car is equipped with ABS then they bleed nipple should be opened rather than the fluid cap opened to wind the pistons back in.

That's mainly (IIRC) to prevent dirt from inside the caliper blocking filters inside the system? I've seen it mentioned on websites for various car maintenence in the past - interestingly, the Haynes for the Mondeo (which has ABS) and many other cars of a similar age makes no mention of this technique, so I don't know if it's system specific or just a general thing.

I remember being concerned after reading this when I first got the car, so I asked a few mechanics I know what they did. The universal response was "nobody bothers with that", so I've never bothered doing it.

 

[Lopéz]

When i took my front breaks apart to inspect for grit and the like because they were squeaking (infact still do!) I never used a clamp or winding tool.

My mondeo looks the same as yours but where u have used that tool on the piston there is just a hole on my caliper. The back of the break pad had a simple metal spring on it which slotted into this hole.

I don't understand why it is different.

It's not different - I've only photographed the caliper with the tool in place.

Look:

That's the caliper fully rewound. On my old Sierra I could push the caliper in by hand, but for the given effort it's easier to use a clamp or winder.
Incidentally, if you are just cleaning the brakes and not renewing the pads you won't need to push the piston back in because the pads are staying the same size. As the pads wear over time, they get thinner - this means the caliper piston has to push out further and further to apply the brakes. So when you come to put in new pads, they don't fit in the gap because the piston has come out too far.

 

[Lopéz]

Worth noting that some calipers need winding in rather than simply forcing back in. My rover and lots of honda's need the rear calipers winding in.

Yup, winding tool has a proper locking attachment for those - the Cossie calipers I put on the back of my Sierra had to be wound, the piston has patterns cut into it for the winding tool to lock against.

Also the brake warning like should come on at the correct time when they need replacing again.

This is bangernomics! Pads with wires cost more you know young man!

 

[Lopéz]

I will be doing a thread this weekend on oil changes.

Glad to hear it! The more tech stuff the better as far as I'm concerned. Dogbreath, are you listening? I'm sure you can re-hash your cam cover painting guide and pics as well as a few others from over the years.