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[robson]

There appears to be a lot of disagreement on whether to open the bleed nipple when pushing brake cylinders back or whether to push them back slowly with nipples closed. After having applied the brakes and then released the pedal surely fluid is flowing back towards the resevoir isnt this the same as pushing the cylinders back although there is obviously a greater volume of fluid being transferred. What are your thoughts as far as seal reversal during pad change.

[Webby the Bear]

you should pinch off the brake line with vice grips (put two pieces of fuel line on to the pincers to protect hose). then open bleed nipple. then push piston back.
this will guarantee no fluid will be forced up to the master cylinder

HTH

[Webby the Bear]

....Do remember to top up the fluid resevoir in the engine bay though 

[tidla]

I see the logic, as your getting old fluid out the caliper and nice new stuff in the reservior.

Theres always a chance of snapping of the nipple off of course..

The only time i have had a problem was on a 95 astra, but the chances are the master cylinder was on the way out anyway.

[Nick W]

I've never worried about it in 25 years. This is because I've never had a problem.
As for clamping the hose, opening the bleed nipple and then moving the piston back, surely that is going to create an air pocket? And a procedure that means you HAVE to bleed the brakes after a simple pad change is an unnecessary complication.
I should add that I have a tool specifically designed to clamp hoses that I've never used as I don't like the idea of crushing a rubber hose.

[Webby the Bear]

I've never worried about it in 25 years. This is because I've never had a problem.
As for clamping the hose, opening the bleed nipple and then moving the piston back, surely that is going to create an air pocket? And a procedure that means you HAVE to bleed the brakes after a simple pad change is an unnecessary complication.
I should add that I have a tool specifically designed to clamp hoses that I've never used as I don't like the idea of crushing a rubber hose.

No it won't. You're forcing the old fluid in the direction of the bleeder where the fluid is expelled. No air is allowed in as you also use the ''brake fluid recovery resevoir'' (tube from nipple in to a bottle where the tubing end is submerged in fluid).

Note the fuel line on the vice grips stops the crushing of the brake hose 

See here for it in action. 

http://www.youtube.com/watch?v=3kf8C4Qxu-A

[TheBoy]

Clamp hose, open nipple whilst forcing piston in.

As well as protecting master cylinder, it also gets the shitty fluid out (the fluid nearest the piston is the most abused, yet doesn't get changed as part of a normal brake fluid change/bleed).

[Webby the Bear]

Clamp hose, open nipple whilst forcing piston in.

As well as protecting master cylinder, it also gets the shitty fluid out (the fluid nearest the piston is the most abused, yet doesn't get changed as part of a normal brake fluid change/bleed).

 

[robson]

Thanks for the replies I must say that I tend to agree with Nick W I also have a tool to clamp off brake hoses but do not like the idea of crushing the hose. As for that bloke on the video I have watched him before and I would not like to give him my car for repair.

[Kevin Wood]

I don't bother clamping the hose, personally. If the bleed nipple is open you will create a much easier path for the fluid to escape. The main objective (on an Omega) is to prevent pressure building up and dislodging the master cylinder seals.

I also want to be rid of the fluid that's been sitting in the cylinder getting hot, and, if you don't loosen the bleed nipples every 6 months or so, you'll probably find they sieze and shear off when you next need to open them, so for a little extra effort, it's worthwhile, IMHO.

[feeutfo]

Pushing the piston back is MUCH easier with the bleed nipple open, too.

I never clamp the hose either, unless there's another issue... open nipple with pressure applied to the piston, and you control the piston retracting with the bleed nipple opening and closing. You'll feel the pressure release on the piston, as the nipple opens. Close nipple as the piston reaches fully home.
Apply brakes once work is done, to force the pistons out again and set the new resevoir level, then top up the reservoir. When fitting new pads your then sure the level is correct.
It's quite common to see a full reservoir with worn out pads, then when new pads are fitted and the owner does not open the nipple, there's too much fluid in the system when all the fluid is pushed back up to the reservoir.

Etc etc. open the nipple.



But the main thing is to get the old fluid out from calliper piston, the main cause of spongy brake pedal.