# If i remove caliper piston, must i bleed the air in the brake system?



## eikido (Sep 24, 2010)

I need to remove the caliper piston because i need to rebuild it probably because of rust (the wheel is not turning freely when the car is jacked up, the brakes are pushing on the disc even with no brakes applied).

If i remove the caliper piston, do i need to bleed the air in the brake system on all calipers? = (Will there be brake fluid coming out if i disassemble the caliper piston)


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## rogoman (Dec 16, 2004)

Replacing a caliper will require bleeding of the brake system at that caliper. You do not have to bleed the other calipers; however if brake fluid happens to continue dripping from the open line and empties out the master cylinder, then all calipers would need to be bled.


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## eikido (Sep 24, 2010)

I will not replace the whole caliper, only remove the piston in the caliper to add brake fluid and then reinstall it. Will i still need to bleed?


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## IanH (Feb 11, 2003)

To do this the most simple way, yes you can just bleed the one caliper.
Make sure you put the caliper on with the bled valve pointing up.
To do this note the following. 
As stated above you must not let the fluid drain from the master cylinder. I found the best way to do this is before you start top up the master cylinder all the way to the top.
Then get a new polyethylene bag, a Zip food bag works for me, and put over the top of the cylinder reservoir, so its double thickness, then screw on the cap. this needs to be air tight.
Now the master cylinder will not drain out.

now removed your caliper, catch the little fluid that does drain out, it should stop very quickly, do your repair, replace caliper etc. When done remove the poly bag, and open bleed valve, let fluid drain through a piece of clear plastic into a glass jar, stop, and re-top up. check fluid is clear with no bubbles. do a two person bleed if you need to.
tighten bleed valve and press down on brake, pads will take up slack, do it again, and pedal should be hard after about 1 inch of travel.


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## IanH (Feb 11, 2003)

I dont think you should remove the piston and service the caliper bore on the car.
This needs to be cleaned before re-assembly carefully, and only using compatible chemicals otherwise the rubber will fail causing brake failure.

Yes you can re-build this yourself but you must follow the directions and keep it clean, reassemble with the correct rubber grease and brake fluid.


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## IanH (Feb 11, 2003)




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## eikido (Sep 24, 2010)

Cool mate. Thanks.
I didn't remove the piston to service it.
I just changed pads but did push the piston in twice to soften it a bit.


Still not very good, the brake pads are still a little bit on the discs. The wheel turns only about one rev when i spin it by hands.
Not sure what to do.


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## IanH (Feb 11, 2003)

Ok, it normal for this not to turn easily when assembled.
Two things to think about, this is FWD, and you are turning the axle and gears in the diff.
and the wheel bearing is tight, even when used. If its loose, replace it ....

make sure the caliper slides back and forwards. this again is not loose, but should move ok under hand pressure.

So I don't think you have a problem.


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## IanH (Feb 11, 2003)

And the pads knock back under driving condition's, they will rub if you press the pedal down then try to hand turn.


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## smj999smj (Jan 1, 2006)

You'd be better off installing a reman caliper and new brake hose, IMO, then try to rebuild the original, IMO.


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## lukesSX (Feb 17, 2010)

Properly cleaning the piston and bore sucks and that is even with the right tools, lol. If it's rusted out you're probably better off just getting a new or remaned caliper.


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## STEALTHY SENTRA (Sep 1, 2009)

replace the caliper and bleed the brake system,is it really all that much harder to do? collapsed brake hose is possible cause,change also!


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