Drum Brakes and Dumb Mistakes

Drum Brakes and Dumb Mistakes

In a shop environment, this situation would have been a profit killer for sure, which is another reason why I'm so impressed with techs that can turn the so-called easy jobs like brakes, suspension and alignment fast enough to make real money. Sometimes, even the easy stuff, isn't.

In the thirty years that I’ve been messing around with cars and light trucks, I’ve accumulated what I like to think is a good working knowledge of light vehicle repair. Some came honestly, like learning about the importance of bolt torque by blowing the engine in my mother’s Datsun 1200, some by the back door, like combining three Austin Mini’s (the original, small one) to make one vehicle that could be registered three different ways. This week, however, I had a head scratcher that drove me crazy enough to want to describe it here. See if you can relate. My winter beater and general parts/cottage supply/lawn tractor hauler is a clean 1990 Dodge Grand Caravan, 3.3L V-6, A-604 Ultradrive, etc. etc. It’s ugly as sin, but it works, and it’s simple enough that I generally do the little things myself, just to stay sharp. This week, it was rear brakes. Regular readers know that I like drum brakes and firmly believe that for the average driver, they’re all you really need are simple to service and are cheap. The rears on the Dodge in question are the classic Bendix ‘Duo-Servo”, which means that you can do the job in your sleep, with a hangover. And because I like to do brakes about once every ten years, I elected to replace everything from the backing plate out. I assembled everything, backed in the adjuster, repacked the wheel bearings, tapped in a new grease seal, offered up the drum and … it wouldn’t fit. Recheck the adjuster screw. Yes, it’s all the way in. Try again. No way. This time I check to see if I’ve inverted the primary and secondary shoes. No problem. I then check the drum I.D., which is within spec, and the thickness of the shoe linings, which were also fine. The parking brake was fully off and not seized. Still the drum won’t go. What do you do? Perplexed, I tore the entire system down and started again, assuming some kind of assembly error. This time I’m slow and careful, checking the manual as a precaution. Still the drum won’t fit. Anger/frustration and bewilderment set in. I’ve done this hundreds of times before, on everything from Imperials to M.G. Midgets, so how can I be stumped on a Chrysler minivan? The next step was to check the part numbers on the name-brand replacement parts. Drum, shoes and hardware kit are the right numbers. Comparison with the old parts show them to be the same. The situation can’t be happening, but it is. A couple of sips of one of Molson’s better products and I attack the problem anew. This time, armed with more light and with a better attitude, I notice that the shoes aren’t both touching the upper anchor pivot at the same time, even with the adjuster backed off completely. Closer inspection shows that the parking brake strut is holding the shoes apart slightly. It’s in the right way around and it’s forked into the shoe webs correctly, but still the shoes are jacked outward. Digging into the garbage can, I retrieve the small, flat coil spring that keeps the strut from rattling. The replacement part uses spring wire that’s at least twice the thickness of the original, so the coils bind when the shoes are compressed inward. Not by much, but the combination of new shoes and a new drum left not enough clearance to put the lot together. No, I wasn’t going nuts, but I was let down by a name-brand aftermarket part that was well-made, but just didn’t fit correctly. I’m not going to name the company, because I can’t tell if this is a one-time or systemic problem, but it did teach me a lesson or two about doing the simple jobs. One is that you can’t get complacent, no matter how easy the job looks. The other is to trust your instincts. I should have assumed that I put it together correctly in the first place, rather than rebuild the brake again, wasting time. In a shop environment, this situation would have been a profit killer for sure, which is another reason why I’m so impressed with techs that can turn the so-called easy jobs like brakes, suspension and alignment fast enough to make real money. Sometimes, even the easy stuff, isn’t.

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