Brake failure post mortem

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May 10, 2007 | 10:00 PM

Corey872

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Brake failure post mortem

Had a chance to tear down my front brakes the other day. Regular readers will remember my post last week about the drivers front brake locking up on my cross-town drive which resulted in enough heat to melt the plastic "dog bowl" hubcap off the wheel.

I tore down the caliper and found out that one of the pistons had a missing rubber dust boot. Didn't look like it was melted or eroded, it was just gone like someone had ripped it off. The left side (arrow) is the problem. The missing boot let water in which caused rust around the piston.

The rust lodged between the plastic (yes, plastic!) piston and the cylinder which locked everything up good.

You can see the scores on the piston.

A couple of revelations about the calipers...no auto parts store in town had them in stock (this is a three year old "most popular selling truck in America") and no one stocks brake parts! Also, no rebuild kits...it's the complete caliper or nothing! The other thing that blew me away was the plastic pistons...of all places to save a pound or two...Next time you are hauling down that 9000 pound load, think of those little chunks of plastic at the end of the brake pedal!

May 10, 2007 | 11:50 PM

edgl

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From: Lancaster, CA

Can't you upgrade to a steel piston? You pay so much money for a truck, and they give you plastic brake pistons. If you are hauling something, you have to use more braking, which will cause these plastic pistons to get very hot.

May 11, 2007 | 12:03 PM

Corey872

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I noticed that some of the calipers for the '04 heritage had a 'heavy duty steel piston' option, but that didn't appear to be the case with the 04-up new body.

On the plus side, my wheel/brake combo got hot enough to melt the hubcap off, the pistons survived with only a little flaking of the plastic on the pad mating surface. The parts list I saw said 'phenolic piston' which is probably glass fiber reinforced phenolic. That is a thermosetting plastic which means once it is molded, it won't 'melt', but it still blew me away to see the two lumps of plastic!

May 11, 2007 | 01:54 PM

schneidz

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they are canvas/linen phenolic pistons, this material is used to move trains and its plenty strong for what they are being used for and i don't think it was a cost savings measure in the least bit but instead a superior engineered material used in this circumstance.

May 11, 2007 | 02:37 PM

Tylus

MMNC (SS)(Ret)

Joined: Mar 2004

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From: SE Georgia

phenolic = wood

the Navy uses it as a bearing on the propulsion shafts that are subject to seawater. the material is very durable

May 11, 2007 | 08:29 PM

Ferguson65

Logistics Pro

Joined: Mar 2005

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From: southeast PA

This isn't the fist time Ford has used the phenolic pistions. Don't know the history on your truck, or miles, but I'd bet that dust boot got in someone's way when doing a brake job at some point and it just got tossed. There are some very bad dealer "techs", and I used to work for a dealer that had quite a few of these hackers.

May 12, 2007 | 10:18 AM

Ryan50hrl

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Joined: Nov 2001

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From: Neenah, Wisconsin

my 95 had plastic pistons.....and i'm guessing no one carries calipers because for the most part, these trucks are too new to need many major repairs yet.....