Hagerty.com

When do-it-yourself isn’t the best way to go


#1

We all embrace some automotive jobs with vigor and, for whatever reason, steer clear of others. Sometimes the deciding factor is early success or failure at the attempted repair. For example, a few years ago, I dyed some faded seats back to their original color. I found it easy and surprisingly satisfying, and I love the fact that I now have that arrow in my automotive repair quiver.


This is a companion discussion topic for the original entry at https://www.hagerty.com/articles-videos/articles/2018/10/15/when-do-it-yourself-isnt-the-best-way

#2

I am glad I won’t be driving that BMW. The work described constitutes a “repair”, not a “rebuild”. A rebuild would restore the caliper to “as new” condition - a level clearly not achieved. Two critical mistakes were made in that repair. First, all that rust means moisture was present between the dust boot (outer seal) and the hydraulic seal (inner seal). No mention was made of cleaning the rust from this area. Any residual rust here - especially with all that pitting on the piston - will eventually re-seize the piston (more likely sooner than later). Second, that piston is junk and must be replaced. All that residual rust and pitting will prevent the seal from seating and will eventually destroy the all important hydraulic seal. Remember we are trusting our lives on high pressure hydraulics. Even small imperfections will result in leaks. Fortunately pistons are not expensive. Unfortunately they are not included in a “rebuild” kit. A third consideration, particularly in a high-end car, is: was the bore chrome lined? If the bore was lined all that rusting indicates the chrome is gone from the area around the hydraulic seal. Any rough edge of the remaining chrome can damage the hydraulic seal. It will take a qualified professional shop to restore a chrome lined bore to “as new”.


#3

I go with Rob’s first instinct, and that is to buy a new or rebuilt part and not mess around with rebuilding. Were it me, I’d simply paint the rebuilt unit red, and not worry about the “M” labeling. Life’s too short to sweat that kind of stuff.


#4

Agreed! How much can a new piston be?


#5

You’re pennywise and pound foolish!
It won’t last. And what about the other side, or the rears?
Bet it won’t be long before you’ll be doing this again.

I don’t like to spend anymore than necessary but if it were me I would have bought 2 rebuilt calipers and painted them red.


#6

The piston is a bit rusty, but all the rust is past the area where the seal contacts it. I like to use Girling red caliper grease on the outer piston and boot. I don’t see any reason why this won’t be a good repair. And I’ll bet that I’ve repaired a lot more brake systems than anyone else who has replied. But, several hours! Does that include a 6 pack! :grin:


#7

People over think things,pull out the piston, emery cloth the piston and bore replace the rubber parts. bleed the brakes.1/2 hr you are back on the road.paint them red if you want. Just don’t lie to people when you sell it.So many cars for sale today have nice paint jobs over bondo with new cheap china replacements. show car junk, but not anyway close to what it was from the factory . remember when cars where fun and not investments .