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Discussion Starter #1
Hi Alfa fans.

I had what appears to be a common problem - the rear calipers on my Mito seized. They were replaced less than two years ago. I just had an MOT and I was warned that the caliper piston boot is split and letting in dirt, etc. and may cause a future seizure. I asked how this can happen and the mechanic said it usually happens when the piston is twisted to pull it out in order to fit new pads.

Firstly, have I got the terminology right - would it be the piston boot? (I forgot exactly what he said and want to get it right)

Secondly, since I've not had new pads since the caliper was fitted is there any other likely way they could tear in such a short amount of time? Is this a manufacturing fault or a fitting fault? I need to get new discs and pads soon and would like to get the caliper replaced for free at the same time if I can argue the case that the garage fitted them incorrectly in the first place.

Thirdly, and least important, any advice as to how I can see the problem for myself? What does it look like, what's the best access vantage point?

The calipers have lasted less time than the pads!!

Cheers, G
 

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The boot is a bellow-type rubber jacket which goes around the piston and stops dirt getting onto the part of the piston which slides into the seal. Can also be called a gaiter :).

The piston on rear callipers has to be "wound in" to get it to go back in to give clearance to fit new pads and that's probably what he's referring to. I believe it's the handbrake self-adjustment mechanism which is why you have to wind it on rears and not on fronts. You can get tools to make winding in easier, but sometimes people do it with needle-nosed pliers and if you're using needle-nosed pliers you need to be careful not to slip and damage the boot (maybe it's possible being careless with wind-in tools as well though - I'm not a mechanic and have only ever done it a couple of times carefully with pliers).

This youtube clip shows someone using needle-nosed pliers to wind in a rear piston and you can see the rubber boot just around the piston (the black bit immediately around the piston which is not moving)...

To more clearly see a boot/gaiter then at 3 minutes in this clip they show a piston more extended (and a rather grotty looking boot):
[ame]https://youtu.be/wz0fPLqPvIs?t=179[/ame]
 

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"May cause" not "is seized" so they haven't actually failed. All you need is a new seal and clean up. You can only see if by taking off the wheel, in fact I'm amazed your MOT man was able to see it!!
 

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Discussion Starter #4
Thanks both. Would you rule out defective part? All your comments suggest handling the boot is the only way to damage it.
@Skaffen, you mentioned the hand-break mechanism. My MOT said one of the cables was hanging off so they clipped it back on - could that relate to the damage, in your opinion?

Cheers, G
 

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Thanks both. Would you rule out defective part? All your comments suggest handling the boot is the only way to damage it.

@Skaffen, you mentioned the hand-break mechanism. My MOT said one of the cables was hanging off so they clipped it back on - could that relate to the damage, in your opinion?

Cheers, G
A mechanic would probably have a better idea of possible causes - I'm no mechanic! I very much doubt if it would be the unclipped cable though - can't see how it would get anywhere near the boot (in fact it's hard for anything to get in there other than dust/dirt due to the location). Main cause of damage does seem to be during brake pad change when winding it (seems if the boot doesn't rotate freely then it can get twisted as well, or it could protrude a little and get pinched perhaps). Could also be damaged with some solvent cleaners/lubricants I guess that aren't compatible with rubber. If no maintenance has been done in that area since the caliper it's hard to see how it could have been damaged in that time. Was it a brand new caliper or a refurbished/remanufactured one that was fitted?

While googling I did find this video on how to change the rear pads on a Mito so you can see precisely the area in question and how a wind-in tool is used:
 

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I'd find it hard to see without removing a wheel .. and in an MOT they are NOT allowed to remove anything!!
 

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Discussion Starter #7
Thanks for all your help guys, wish i could watch YouTube videos at work, haha!!

The caliper was brand new - £259.95 with fluid, fitted 15-Oct-2016.

The wheel was removed as part of the service that went with the MOT, I suspect. Sorry to be misleading referring to the MOT all the time.

Cheers, G
 

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I don't like to throw accusations around but it does seem that the people who replaced the caliper last time did a substandard job.
It is common practice to lube up the boot as it tends to stick when rewinding the piston back into the caliper. This would prevent the boot twisting, and unless you've had any other work done since then, why wasn't the cable simply clipped back into place?
(Just my own observations as I'm not a mechanic but have done my fair share of work on mine)


Sent from my iPhone using Tapatalk
 

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Discussion Starter #10
@Rockhopper, that price included both rear-calipers fitted. That's £100 cheaper than the red ones the car came fitted with!!
@djelia, The cable was clipped back on, the mechanic's exact words. Just checking if that might have contributed to the defect. i agree, sounds like it was poorly fitted. And if as the earlier thread contributions suggest, that a kit to replace the boots exits, I'd be happy for that solution if the garage are prepared to give up their time.

Just need to have the argument!
 

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That’s slighlt more acceptable then! I had a silver one fitted to replace a red seized one on my car.

Who did the work though? I’m guessing (hoping) it wasn’t Alfatechnico in Huthwaite?
 
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