Replacing disc brake pads.

[daddylonglegs]

Over the years I have had quite a few brake master cylinder failures after replacing disc pads on early rangies and 110's. When fitting new pads you must push the caliper pistons further back into their bores to accomodate the thicker material of the new pads. After doing this if you push on the brake pedal it usually goes to the floor on the first application.this forces the master cylinder piston rubbers to move beyond their normal working stroke and If you have a master cylinder that is a few years old the rubbers may be damaged in a previousely unused and corroded portion of the cylinder bore.
To avoid the extra 200 odd dollar expense of a new master cylinder when changing brake pads, do one corner at a time and once you have replaced the pads on that corner pump the caliper pistons back up with about 4 very short {50mm} strokes of the brake pedal before moving on to the next corner. This way the master cylinder pistons are not moving past their normal working stroke and the rubbers won't be damaged.
Bill.

[RaginRover]

Thanks for the FYI Bill - I will remember to do this on all the cars I change pads on

Tom

[Slunnie]

Thanks Bill, I'd never thought about it before.

[DaveS3]

Thats very useful info there Bill...

Need to do the fronts on the old mans county sometime in the near future.


Dave

[LowRanger]

Over the years I have had quite a few brake master cylinder failures after replacing disc pads on early rangies and 110's. When fitting new pads you must push the caliper pistons further back into their bores to accomodate the thicker material of the new pads. After doing this if you push on the brake pedal it usually goes to the floor on the first application.this forces the master cylinder piston rubbers to move beyond their normal working stroke and If you have a master cylinder that is a few years old the rubbers may be damaged in a previousely unused and corroded portion of the cylinder bore.
To avoid the extra 200 odd dollar expense of a new master cylinder when changing brake pads, do one corner at a time and once you have replaced the pads on that corner pump the caliper pistons back up with about 4 very short {50mm} strokes of the brake pedal before moving on to the next corner. This way the master cylinder pistons are not moving past their normal working stroke and the rubbers won't be damaged.

Bill.

As a further addendum to what you have said Bill,it is also best to crack the bleed nipples and attach a rubber tube to them and place the other end of the tube in a bottle or container.When the piston is pushed in,the old fluid that is held behind the piston,will be passed out the nipple and not allow contaminated fluid to be returned up to the mastercylinder(also a major cause of mastercylinder failure) due to small metalic particles damageing the knife edge seals .When following this procedure it is advisable that the ends of the tubes are kept below the fluid level in the container,in the advent of any loss of momentum when the piston is being pushed back,and hence allowing a small amount of air to be drawn back into the system.When the piston is fully retracted then just do the nipple up and proceed as Bill described above.I have followed this procedure for over 30yrs and have never had a mastercylinder fail due to changeing pads,and I used to specialise on European vehicles,often fitted with ATE brakes and they are not very receptive to mistreatment.
Just my 2 cents worth to ponder

Regards

Wayne

[daddylonglegs]

Thanks Wayne, I admit I haven't done it your way too often in the past but it makes a lot of sense and I will do so from now on.
Bill.

[LowRanger]

Bill,I learned at a very ealy stage of my careerhaving seen a few tradesmen create problems for themselves,when I was working for Mercedes.Glad that I may have been able to shine a small bit of light on this subject,I have read all your postings on subjects regarding Landrovers,and even as a Tradesman I stand back in awe and tip my hat to you.

Wayne

[daddylonglegs]

Thanks again Wayne. There is so much more we all can learn, and the exchange of information from forums like this can make the process so much easier, quicker.and more entertaining.
Regards Bill.

[rick130]

...it is also best to crack the bleed nipples and attach a rubber tube to them and place the other end of the tube in a bottle or container...

the other advantage to doing what Wayne describes is that you eliminate the chance of overflowing the M/C reservoir.
If you use a clear tube, it's surprising, if you shine torch at it, to see how much fine metal, as well as discoloured fluid, comes out.

Great tip, BTW, Bill.

FWIW, I made a pressure bleeder from a 5 litre garden sprayer and the bottle top from, IIRC, a vitamin jar. The diameter and pitch are identical to the M/C reservoir, and I slipped an 'O' ring in it to seal it.
Drilled a hole in the centre, screwed a hose barb in it, removed the spray wand and pushed the hose on the barb.
Voila, an el-cheapo pressure bleeder.
Saves full stroking, and possibly damaging, the M/C seals and piston when bleeding.

Rick.