I've changed out calipers and rotors before, but never messed with rear calipers with pistons that have to be 'twisted in'. Can anyone give me a play by play, that a 5 year old would understand, so I can do the job effortlessly? Pictures would be a bonus.
I'm changing the rotors and pads, and cleaning and painting the calipers.
Thanks.

 

flyrr100, first off, before you start ripping into stuff, make sure you have a tool for pushing the piston in. You can pick up a $10 block from the local auto parts store or you can also rent one of their caliper retracting tools. If you rent the tool, then you need to make sure that it will compress by turning both directions (not all kits do this, actually very few do this).

I will not go into the details of removing the caliper, I think you can handle this without the play by play.

After you get the caliper off of the rotor/mount, get your tool handy that will push on the piston as it also allows you to turn it at the same time. If you are using the block, you can play a little bit and see which direction will cause the piston to remain stationary when turn and which way will cause the piston to move out. You want to turn the piston in the direction that it does not go in.

At this point, using a 10mm wrench, crack open the bleeder port on the caliper and then while pushing the piston in, turn the wrench/piston in the correct direction. You should see some fluid coming out the vent as the piston moves inwards. Once the piston is flush with the backside of the caliper, stop twisting and then close the vent. Just remember, whatever direction you twisted the one side to push the piston in, the other side is the opposite direction. I don't remember which side goes which direction. I use the tool to see which way the piston remains stationary and which way causes the piston to move out.

Once the piston is in flush, you finish up the brake job like any other caliper. Just don't forget to bleed the rear calipers once it is all assembled to get any possible air out of the caliper. I find that when doing this, getting some 9/32" tygon tubing works really well. You can masking tape the hose to the top of the wheel well and do it all yourself since the tygon will keep a column of fluid on the caliper and prevent any air from getting back into the system.

 

Awsome. Thanks. I'll take some pictures once its done. I'm still deciding wether to go for slotted rotors. Some say... All they give is bling!

 

Pretty sure that right side caliper requires turning clockwise to push piston in and left side anticlockwise. Well thats what it's like in the uk.

 

flyrr100, I see the slotted/drilled rotors this way: even if there is no performance improvement, for the price, they are cheaper than factory replacements with no negative effects on the car. So, take that for what you want.

 

thats correct and people ever wonder why firestone, goodyear ntb and indies that dont know what theyre doing always sell new drivers rear calipers to customers because "theyre seized"?
Maybe should have tried turning it the opposite direction before you made your customer by a new caliper just had another one last week from firestone

 

Thermo, why do you recommend cracking the bleeder valve?

When you push the caliper piston back in, the brake fluid just go back into the reservoir where it came from to begin with. I have replaced front and rear pads in my Jag and have never bled the system. Yes, I had to rotate the piston to back off the emergency brake.

Pete.

 

just because its easier to rtract pistons and you can always run into issues with fluid contamination in the mastercylinder. just because because you drive without a seat belt without an accident doesnt meen its a good practice

 

I don't understand the contamination issue. The system remains sealed before, during, and after the brake pad replacement process.

If you crack the bleed valve then you have lost brake fluid. You must then open the reservoir cap to top up the fluid which lets moisture in and possibly some contamination. Why is this necessary?

Pete.

 

Shrug, how does all the black crap get in the reservoir. I replace my fluid every yr or so wether it looks bad or not because brake fluid absorbs water and i live in a humid environment and last thing i need is to start replacing calipers or master cylinders from contamination or rust.

 

The system is not fully sealed. The pads wear and the pistons extend thus fluid is sucked from reservoir causing air to be sucked sucked into the reservoir. That is why the system needs topping up as the pads wear down.

Interesting to read your comments. I totally agree.
It is worth looking carefully at the exposed wall of the piston for corrosion before it is returned into the caliper. In the past I have found one of my pistons, on a Ford, so badly corroded it would have never sealed if I had pushed it back.
In the UK , changing the brake fluid every two years or so is quite common. It does not seem a common practice in the US.
There are simple test kits to check the amount of water in the brake fluid, which should ensure an honest outcome rather than another revenue stream.
When water in brake fluid turns to steam, a spongy brake pedal soon gets your attention

Brake fluid - Wikipedia, the free encyclopedia

An item from a respected UK oil supplier
http://www.opieoils.co.uk/pdfs/tech-...-Explained.pdf

 

jagger, I crack the bleeder valve as I have tried pushing the piston back in without cracking it and I find it next to impossible to do. By cracking the bleeder valve, the piston goes in with little effort.

As for contaminating the fluid, there are tons of rubber products on the calipers. While rubber is a good sealer, it is a very porous material. A finite amount of air and water can make it into the caliper. Not to mention that the brake fluid reservoir is a vented place. Over time, the brake fluid will collect water (as the fluid is hydroscopic, ie, likes to absorb water) and also absorb air, which will cause the fluid to start to turn a dark green color. Getting a mixture of water and air into the fluid will dramatically increase the corrosion inside of the brake system, leading to other failures.

Even picking up a quart of brake fluid is but a few dollars and the time to bleed the brakes is very minimal compared to replacing an ABS module or a brake booster. For me, that is cheap insurance and it forces me to bleed the whole system, putting fresh fluid everywhere.

 

Is the reservoir open to the air on the Jag? I have not looked.

However on every other car that I have worked on over the years there is a diaphram under the reservior cap that seperates the outside air from the fluid. The diaphram is very flexable and moves down with the fluid as the pads wear. When you push the caliper pistons back, the reservior refills and the diaphram moves back to the original position.

I understand that some people may have problems due to their environent and may have to change their fluid. My previous Jag had 200K miles on it and I only had to rebuild one caliper, but that was because a tool slipped and tore the boot while I was compressing the piston and rotating it. In the last 20 years I have not had a leaking caliper on any car foreign or domestic including the Jag. The weather in the northeast US is not all that dry.

Pete.