Is “preventive maintenance” a fool’s errand?

David S. writes:

Do you have any thoughts/rules of thumb when it comes to replacing things before they break? I’m thinking about replacing the original, trouble-free radiator in my 1990 Mazda Miata as preventive maintenance. Am I being proactive or just wasting money?

Rob Siegel answers:

I used to be big on prophylactic replacement of parts in the “Big Seven” systems most likely to fail (if you’re new to reading this column, those are: cooling, fuel delivery, ignition, charging, belts, clutch hydraulics, and ball joints). The problem is that these days, there’s the very real possibility that you’ll remove an old, high-quality original part and replace it with something that’s new but of lower quality. When cars are under warranty, manufacturers work with the vendors who supplied the Original Equipment (OE) or “genuine” parts that were originally in the car. The dealership charges top dollar for these parts precisely because they pass quality control standards intended to help avoid repeat failures. As the cars age out of warranty, there’s little incentive for the manufacturer to police the quality standards of these OE parts. They may still be supplied by the same manufacturer, but production may be shifted to a different country, or the part may be made out of cheaper materials. Thus, the part you still pay top dollar for at the dealership may no longer be identical to what was originally in the car. It’s even worse when you move from “genuine” parts to aftermarket parts (the advertising phrase “OEM quality” is not an actual standard).

Obviously, cracked belts and rattling idler pulleys should be replaced before they full-on fail, but whether to replace an “it ain’t broke” part, and what to replace it with, has become a fuzzy calculation based on the perceived likelihood of failure, the difficulty of the repair, the cost, and whether you’ll feel like more of an idiot if the original part breaks and strands you or the replacement does. The best you can do is read up on candidate parts on enthusiast forums and make an informed decision.

I recently faced your specific problem. Although there was nothing wrong with the cooling system in my 200,000-mile 2003 BMW, I replaced most of it for exactly the reason you list—the aging plastic is known to crack. However, within a month, the brand-new water pump began to weep coolant (the vendor exchanged it). On a 200K daily driver, I’d make the same call again.

Nelson W. writes:

We all know that rust and accident damage are things to avoid when buying a classic car. But is there any mechanical telltale that will make you run for the hills, regardless of asking price? (Not an idle question: I’m considering buying a rust-free 1988 Camaro that clearly has some cooling problems. Owner admits he’s topping off the radiator constantly, and the heater core has been bypassed.)

Rob Siegel answers:

Mechanical? Not really. The more mechanical issues a car has, the better. If it’s dead and being sold at a third of its market value because of it, I welcome dead. Dead I can fix. Rust I can’t. But be aware of just how bad the worst-case scenario can be. For instance, the coolant loss in your candidate Camaro could be rotting hoses—or it could be a cracked head or block. If you feel that that possibility has been baked into the asking price, that you have the time to deal with it, and that you love the car in other ways (e.g., color, condition), fine, but be brutally honest with yourself about the downside.

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Rob’s latest book, The Best Of The Hack Mechanic™: 35 years of hacks, kluges, and assorted automotive mayhem is available on Amazon here. His other seven books are available here on Amazon, or you can order personally-inscribed copies from Rob’s website, www.robsiegel.com.

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