[Shop-talk] Disc brake piston explosion

[Neil Sherry]

That looks like a phenolic type of material (hard plastic stuff). I 
would say that has been caused by excessive heat and/or time.

I had a 1992 BMW that had the waterpump impeller made of similar 
material - they work fine at normal temperatures, but if there is 
overheating (for example when the radiator  or a hose fails and the 
coolant escapes) the resulting overheat causes the impeller to crack and 
fall of the end of the waterpump shaft.
Neil


On 26/01/2015 10:41, eric at megageek.com wrote:
> I don't know what they were made of.  Here is a photo of one of the
> calipers with the failed pistons in it.
>
> http://www.megageek.com/photo/photoa~1.nsf/a7ffeab012bbfb5b85256eb1007ca7f6/d1f76fb58c8f84f685257dd9003a7e29?OpenDocument
>
>
>
> Eric P
> "Be as beneficent as the sun or the sea, but if your rights as a rational
> being are trenched on, die on the first inch of your territory." Ralph
> Waldo Emerson
>
>
>
>
> John Miller <jem at milleredp.com>
> Sent by: "Shop-talk" <shop-talk-bounces at autox.team.net>
> 01/25/2015 10:34 PM
>
> To
> shop-talk at autox.team.net
> cc
>
> Subject
> Re: [Shop-talk] Disc brake piston explosion
>
>
>
>
>
>
> On 1/25/2015 7:34 PM, Tim . wrote:
>> Any ideas what caused it?
>>
>> "F350 pick up."
>>
>> sorry. couldn't resist.
> Are they steel pistons?
>
> Ford tried phenolic-resin pistons in several applications a while back,
> and they were notorious for coming apart in heavy use.
>
> But it would surprise me a LOT if Ford went down that road in something
> like an F350.
>
> John.
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