Front Brake Piston - No Way In! URGENT HELP PLEASE

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Sahand
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Front Brake Piston - No Way In! URGENT HELP PLEASE

Post by Sahand »

Hi all,
Using the previous posts in this excellent forum, I decided to replace my front brake pads and discs last week cause of the shakes when braking.
Unfortunately the calm weather changed to a heavy rain as soon as I began the job! So I just hanged the opened calliper and left the remainder for a better time.
As I am so lucky (!) my wife later started the car but hopefully she realized something wrong in it at the same time, as she couldn’t stop the car using the pedal (seems normal I think).
Today when I tried to do the remainder I noticed the piston about an inch out (from body of calliper) and after hours of winding it with gentle push I knew there are no chances of it returning back to the place. There is also LHM leakage around the piston as I wind it (No leakage before). The piston is somehow loose in place and I heard some sound like sucking air from the surrounding rubber when I pushed it around.
I am really stuck in and even tried to call a mechanic which I forgot about it when I knew they’ll charge me £35 init. + £28/hour!!
Please help me to sort this out somehow!
Thank you all
Sahand
Richard Gallagher
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Post by Richard Gallagher »

It sounds as if the piston has been pushed out of the caliper. If so you need to make sure that the rubber seal around the piston is seated correctly as the piston is pushed/screwed back in.
If this is the problem and you cannot get the piston to seat correctly then it might be easier/cheaper to get a replacement/secondhand caliper.
Sahand
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Post by Sahand »

Thanks Richard for your reply.
The piston has not been completely out of caliper. I tried to move it away gently to see if it dismounts but it didn't. I also pushed the seal away to see if I can see the end of piston which caused more LHM to flow out! I am not clear about "seating correctly" as you said, but it's surrounding the piston.
I read in some posts that it takes a long to wind it back. I tried for half an hour (maybe more) but it didn't move! Also I can wind it easily by hand! Any suggestions? Thank you again.
JohnCKL
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Post by JohnCKL »

The piston can be wound back even if it dismounts completely. My friend's situation was the same. Just take patience and time. Try to align the piston correctly to screw it back in with a little more force. It does take a long time to do it but can be done. Good luck.
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Post by Richard Gallagher »

Ideally to screw the piston back in you would you a 'Wind back tool' which applies the required pressure to push the piston back.
As John states, you do need to apply quite a bit of pressure to the piston in order to get the thread to engage. The problem you then have is getting the leverage to turn the piston. Try wedging the caliper and then using a square shafted screwdriver or similar tool to wind the piston back.
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np
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Post by np »

I use a wood chisel for the pistons.I cant remember the size(20mm i think)Its nice & flat & fits across the piston nice & tight.
Sahand
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Post by Sahand »

Thanks friends. I am going to try the chisel as I could not find any 'wind back tool' nearby! Any suggestions on these issues:
1. What about the LHM leakage when I turn the piston? Is it the way it should be when piston is out, or some seals are broken?
2. Also I noticed an spring in diagrams which engages with the small hole in piston (very small hole in the top face near the edge). Should I see the end of spring through the hole? I'm worried if the spring has been displaced during my tries.
Thanks again for your helpful hints :)
bxbodger
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Post by bxbodger »

I think you may have damaged the calliper seal or unseated it-the piston should wind back easily, especially with a bit of LHM to lubricate it. The piston probably won't wind back because its snagging on the seal- the best thing you can do now is to bite the bullet, and wind the piston right out and make a visual check of the seal.
Sahand
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Post by Sahand »

What should I do to wind it back in regards of LHM? I don't know if LHM pours out when I move the piston out as now it leaks with each movement and I don't know how to stop it! tnx
oilyspanner
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Post by oilyspanner »

The LHM may be stopping you from getting the piston back in, it may help you to remove the bleed nipple to prevent fluid pressure from stopping the piston once started, you will need to bleed the brakes anyway.
Stewart
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Post by Richard Gallagher »

To stop the flow of LHM you need to GENTLY clamp/pinch the flexible brake hose. If you do not have the correct tool, only a couple of quid, you can improvise by using 'Mole Grips'.
Make sure you understand the importance of gently clamping the hose. If you flatten the hose by overdoing it then you will damage the hose, the rest does not bear thinking about!
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Gregg1100
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Post by Gregg1100 »

Hi,
Just a thought. Can you adapt a valve compressor with like a ball inbetween the fingers, then you can still screw in the piston whilst putting a bit of force to the job
Greg
Sahand
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Post by Sahand »

Hi all, finally did it using your kind hints[:)]
I think the only problem was the bleeding nipple! I unscrewed it a little and tried to align and wind the piston back, and wow! it became hard! I wind the piston back completely using a <b>15mm flat spanner</b> (suggest you try it next time - it is so easier). Still some questions if someone helps me [:D]
1. There is a delay between the time I press the pedal until brakes applied. Is this because of air in system? I bleed the wheel I was working on; should I do it again and/or on other wheels?
1. The LHM coming out from the nipple was something between brown and black (dirty) however one leaking from piston is in good green condition. Any idea?
2. There is still a little leakage from around the piston. Is it something to worry about or will stop after a while?
3. Tried to open calliper on the other side but I couldn't remove the pin even using loads of WD40 [:(] I am worried if more hammering (!) damages the head of pin so it never comes out! It is also rustier than the other! What should I do?
And at the end [^] I was always thinking I am not so lucky, but this time's different [8D]. Surprisingly the car stopped shaking by just replacing this disc! Rear discs were in a worse condition than the fronts and I didn't expect the shakes being solved by just replacing the disc which had the lowest amount of wrap!! Thanks again [:)]
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AndersDK
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Post by AndersDK »

1) Air in the brakes ! Bleed again.
1) Try bleed some more as rust collects in the bleed nipple, it may simply be flushed clean.
2) This is a serious problem. Try clean it up as best you can with rags to see if it stops. If it still leaks you better find a replacement caliper. Note that the brakes are the only thing keeping you and other trafficants alive ! Brakes can not be in fair to good condition - they MUST be in perfect condition.
3) More WD40 - wait a couple days - more WD40 - wait ...
Patience pays here ...
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