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alfa per la vita Alfasud
Joined: 02 Jun 2014 Posts: 32 Location: France
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Posted: Tue Nov 18, 2014 9:06 pm Post subject: Rust in the brake caliper cylinders |
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Hi everyone,
so now that the engine of my 16v is running (for now!), I thought that it would be good to check the brake calipers too.
I took them out and some of the cylinders had rust in them. Pistons look good though.
So I decided to try to save the calipers by honing the cylinders (with a 10€ honing tool that you put on an electric drill not the best but I do with what I can afford!). It got most of the rust out, but there are some rust stains that still remain even after several passes (one or two per cylinder). Their size is roughly the one of a pinhead.
So my questions are :
is it very bad or even dangerous for brake operation
and
can I try to go harder on these rust spots (maybe with sandpaper?) because from what I understand, the cylinder mostly acts like a guide for the piston, the actual sealing coming from the oring inside the cylinder?
Thanks! |
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RFlower Alfa 33
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Joined: 17 Feb 2004 Posts: 432 Location: S of France
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Posted: Thu Nov 20, 2014 1:26 pm Post subject: |
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I don't think you need bother about rust stains too much. As you say, the seal is between the (chrome plated) piston and the "O"- ring.
If the marks are as small as you say they may be pits (tiny holes), which will possibly mean removing too much metal to get rid of them.
I usually polish out any marks with very fine emery cloth or wet & dry paper on a finger.
If this does not work, I take a strip of emery cloth a bit narrower than the depth of the cylinder, put one end of it into a lengthwise slot in a piece of approx. 5mm diameter rod and roll it anticlockwise around the rod to form a tight roll a few mm smaller than the cylinder.
Using an electric drill to spin the abrasive roll inside the cylinders makes the end fly out against the cylinder wall like a flap wheel, making a fairly gentle honing action. _________________ Dick Flower, Nr. Carcassonne. '94 Trofeo 1.4 ie (F), '93 Imola 1.3/1.4 ie (now for breaking) (F), '91 1.7 ie (GB)(spare car), '86 Sprint 1.5 QV (F). '87 VW Syncro camper (F), '73 NSU Ro80 (F), '99 Fiat Seicento (F) |
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alfa per la vita Alfasud
Joined: 02 Jun 2014 Posts: 32 Location: France
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Posted: Mon Nov 24, 2014 10:35 pm Post subject: |
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Thanks for your answer.
So I managed to rebuild the front brake calipers easily.
The rear ones, on the other hand ...
Does anyone know a trick to get the circlips of these ones back to their place ? They have to go all the way down in the brake cylinder but during the process they are also submitted to the opposite force of the strong spring of the automatic brake lever adjuster... This really is driving me mad! |
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RFlower Alfa 33
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Joined: 17 Feb 2004 Posts: 432 Location: S of France
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Posted: Tue Nov 25, 2014 11:59 am Post subject: |
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Sorry, I don't know anything about rear disc brake calipers. _________________ Dick Flower, Nr. Carcassonne. '94 Trofeo 1.4 ie (F), '93 Imola 1.3/1.4 ie (now for breaking) (F), '91 1.7 ie (GB)(spare car), '86 Sprint 1.5 QV (F). '87 VW Syncro camper (F), '73 NSU Ro80 (F), '99 Fiat Seicento (F) |
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alfa per la vita Alfasud
Joined: 02 Jun 2014 Posts: 32 Location: France
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Oggie Green Cloverleaf
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Joined: 06 Mar 2008 Posts: 811 Location: Whitehill
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gritsop Green Cloverleaf
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Joined: 23 Apr 2003 Posts: 766 Location: Ekali, Athens - Greece
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Posted: Thu Nov 27, 2014 6:46 pm Post subject: |
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Hi
The rear calipers are more complicated to repair. Once you remove the piston (removed by turning CCW or acting on the handbrake rachet) you have to remove the handbrake mechanism also in order to make a perfect seal restoration. The caliper internals have a high tension spring which is kept in place with a circlip. This circlip can only be re-installed (removal can be easy) with the help of a long tipped circlip pliers.
Have a look at my website on the ABS installation article. I have shown the process needed to completely tear down the rear caliper.
http://www.alfa-restoration.co.uk
regards _________________ Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive
http://www.alfa-restoration.co.uk
Parts Shop: www.alfa-restoration.co.uk/shop |
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alfa per la vita Alfasud
Joined: 02 Jun 2014 Posts: 32 Location: France
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Posted: Mon Dec 22, 2014 10:26 pm Post subject: |
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Thanks Gritsop that was exactly what I was looking for.
However one month later I still have not managed to do it!
My problem is always the same : as I compress the spring it tends to bend and the piece that goes on top of it cannot go totally down the cylinder because of this (I hope I'm clear enough).
I've tried many things, like making an insert from an old brake piston, using various clamps, etc. but so far I could never make it!
I'm really desperate right now up to the point that I am seriously considering buying second hand rear brake calipers as a replacement!
EDIT: finally found a way to complete the job! It is quite tricky indeed. In my opinion the system is poorly conceived because the circlip/snap ring which acts as a retainer for the handbrake return spring really is undersized. After a few checks playing with the mechanism it even snapped off once! I managed to put it back again in place and now it seems to hold on correctly but this is quite scary... What would happen if it snapped off again at highway speed ? |
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alfa per la vita Alfasud
Joined: 02 Jun 2014 Posts: 32 Location: France
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Posted: Sat Dec 27, 2014 10:27 pm Post subject: |
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OK I have tried several times the handbrake mechanism and it seems OK for now. I am still a bit suspicious... Does anyone have ever heard of any accident involving this kind of stuf? Do you think that if the inner return spring went off while rolling it could suddenly lock the handbrake on the wheel? This is a serious question...
Thanks in advance! |
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Oggie Green Cloverleaf
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Joined: 06 Mar 2008 Posts: 811 Location: Whitehill
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Posted: Sat Dec 27, 2014 11:14 pm Post subject: |
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Just leave the car in fear if your unsure. _________________ PHAT 33 |
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eagle3 Alfa 33
Joined: 11 Nov 2007 Posts: 402 Location: France
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alfa per la vita Alfasud
Joined: 02 Jun 2014 Posts: 32 Location: France
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Posted: Sun Dec 28, 2014 8:43 pm Post subject: |
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Oggie:
Ahah yes you're right! In fact I should have walked away from the car the day I saw it! But whith the amount of time and money I put in it it is too late now
eagle3:
Interesting link that I will definitely keep close at hand if I feel anything going wrong! I have been fiddling with the parking brake mechanism all day long and it seems ok this time. I will give it a test on the car this week (I will be rolling at slow speeds in an empty parking lot...).
I think the main problem with these retaining rings is that they are "inverted" circlips. Been searching a little about this, here is what I found so far...
Regular circlips offer a good, evenly distributed contact around the groove as it is shown here:
Inverted circlips are very different and most of the force is applied on the main lugs as it is shown here:
So one can understand that a small error of positionning will make it go off the groove!
I wonder why they choose to use this type of circlip on these calipers... Inverted circlips are only used when there is something that will spin through the circlip (hence the inverted lugs), however on this mechanism it is clearly not the case. Strange! |
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Oggie Green Cloverleaf
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Joined: 06 Mar 2008 Posts: 811 Location: Whitehill
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Posted: Mon Dec 29, 2014 12:07 am Post subject: |
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Sorry I actually meant leave the car in gear haha iphone typo. _________________ PHAT 33 |
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