Is “preventive maintenance” a fool’s errand?

Illustration by Magnifico

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.



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,

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    Like Rob, all of my vehicles are well used. When I am able I like to purchase the parts most likely to fail, but I usually wait until things are broken to replace them. Too many times the factory part has still been in good condition or is even repairable. Way too many times the aftermarket part is clearly of poorer quality, and there just isn’t much to do about it. You have to account for the poor quality in the future maintenance of the vehicle in that once replaced, that part WILL need replaced again. On modern vehicles, if you are simply trying to prevent being stranded (rather than trying to avoid needing repair work at a less convenient time), parts like electric fuel pumps that don’t give many symptoms of failure are going to be your biggest headache.

    For me it depends. The author brings up a real problem with aftermarket parts. But as for specific things like a 33 year old Miata radiator, I would change it out as a unnoticed failure will have a catastrophic over heat leading to very expensive engine repairs. If the radiator is not black but greenish/Brown replace it before it blows. Mine did 3 blocks from my house! They are inexpensive (under $100) and easy to replace.

    A lot has to do with the type of vehicle, the parts involved and just what expected issues are.

    Some things are just more critical than others. You just need to use some common informed sense.

    Good case is like on a V6 Fiero that is driven in the rain or washed often it is good to change the real plugs once every other year. They will rust in and if you change them no issue. If you do not change possible broken plug in the head.

    Now on my Corvette I just bought. I had no idea of what care it had. I checked and tested the fluid and changed those that were needed like brake Fluid and oil. The Antifreeze was like new tested.

    I did toss on some new belts as it was easy and changed the plugs and wires. Heat is hard on them on the Corvette.

    The hoses are in good shape so i let them go for now. But if I have to Change a water pump I will change the hosed then.

    Same on cars with timing belts. Change things while they are off like a pump and belts.

    Vettes with LS engine can need a new Balancer as they can spin on the hub with age. If you replace it so the water pump and oil pump and front seal while there. If you want a cam it is a good time to do it now. Same on timing chain.

    Radiators don’t just blow, there are tell tale symptoms ahead of time. My 92 Miata still has the original radiator, and it will have until I have a valid reason to replace it. Pay attention, don’t get carried away and remember, it’s not an adventure if you know you are going to make it. Old cars are not for everybody.

    I agree with 77GL. On my 92 Miata, bought new, the radiator started seeping where the core was crimped to the plastic header tank. Nothing catastrophic, just a small top up required, giving time to get one delivered from Rock Auto while still driving and on the Miata a simple job to replace. Unless the core is rotted from salt driving, I think that is the usual failure mode and not a panic situation.

    It absolutely depends. On some things it is money well spent. On others unless the factory part is looking worn the original “OE” part is possibly better than the new “OE” one if suppliers have changed.

    Rob’s articles are some of the most reasonable you’ll find these days! As a fellow thrifty mechanical engineer, I find his tomes spot-on in most cases.

    My preference has always been to avoid replacing parts that don’t need to be replaced, unless a related part is being replaced and a part is nearing its expected lifespan. This is more about not paying for labor twice to get to the part being replaced. Even so, that doesn’t happen too often.

    As I have discovered over the years, the time when I think a part is on it’s last legs and when it actually is are drastically different. Very few parts have failed on our vehicles, even those nearing twenty years old. Now, if I was working with a very old car, I might have different thoughts. But for cars built in this century, I choose to save the money.

    I couldn’t agree more. I have a 97 Ram truck that I don’t use very often and it would shock most people that it still has all its original belts and hoses along with the radiator. I’ve taken it out of state for parts retrieval and I trust it more than most cars out there. In the last 10 years, the lack of quality in replacement parts has changed my mind about replacing a part until needed. I never use to be that way but times have changed for the worse. New definitely doesn’t mean better in a lot of cases today.

    Agreed on waiting on the radiator. The OE one in an Acura here failed by developing a crack in the upper tank after 15 years. It was inconvenient, but not catastrophic. The car was driveable home without even having to top off until getting home. No damage done, and temp gauge never left usual indication. Second radiator failure was the replacement, which developed a leak between core and lower tank. Not even bad enough to sweat over, as topping off overflow reservoir once a month was sufficient to keep system full until I replaced radiator nearly a year later when the weather was nicer.

    The advice for buying mechanically imperfect vehicles is spot on. Be realistic about downside and the appropriate discount and most times you’ll be pleasantly surprised.

    I agree that I will take an entire drivetrain replacement over rust any day of the week

    I work at an industrial facility that used to be very big on routine preventive maintenance. What we learned over time is that having someone touch something that was running fine or replacing a working component with a new part can lead to failure at an alarmingly high rate – and our attitude has changed quite a bit over the last decade or so. If failure of a component is a nuisance, then leave it go until it shows some sign of degradation. If failure of a component can cause significant collateral damage – that should be on the routine replacement list

    For cooling systems in particular, a pressure test will reveal weak areas and active leaks, even block and head cracks.

    I would not replace a radiator in a 1990 Miata unless there was good reason to do so. I can say that because I have a 91 626 Hatchback with it’s original radiator in fine shape. Now with 11 cars one could get crazy being that preventative. All routine care is done religiously which many people don’t do and so my cars run flawlessly. Now I do have a garage well stocked with parts for these cars that might fail. I have been dealing with an eBay seller, for 12 years, who has a fantastic ability to find NOS and US Made OEM parts at great prices. I run across something I buy it. This week a TRW FE OEM water pump, a Clevite OEM FE double roller timing chain, NOS 91 Mazda front wheel bearings, an impossible to find OEM pistons for the 91 Mazda and NOS Motorcraft starter solenoid for great prices.

    I constantly am dealing with the above issues, Rob! Instance: I have a good friend who has a 1971 Karmann Ghia which is all original–just as it rolled out of the factory doors at Osnabruck! I have warned him about allowing some shop to switch “old parts” for new parts. That would immediately destroy the authenticity of his car (only 35K original miles). Another instance: a fellow contacted me about his acquisition of a 1974 Original VW Beetle SunBug. This was a Special Edition which Wolfsburg rolled out–cost more but sported accessories which no other Beetle demonstrated. The fellow, surmising that since the car was “old”, he should should replace parts. He began with the carburetor–an original, German Solex, highly desirable Carburetor. He purchased a Chinese Carb and installed it. He gave me the German Unit. I returned it to him informing him that he had just degraded his car’s unique heritage. He had the German Carburetor professionally remanufactured by a Specialist. But, I could not convince him about the other “old” things which he consistently was replacing–simply because they were “old”. Pitiful! But, this is happening at an alarming rate! It is a bottomless trap into which many vintage car collectors are falling. The cheap price of
    after-market parts is so alluring. What a shame!

    When we got married, my wife had a Fiat 128. The owner’s manual said nothing about the timing belt being made out of peanut butter, and it stripped out in something like 40,000 miles, taking several valves with it. The SERVICE manual did say that it needed replacement at ridiculously frequent intervals.

    Bottom line here is that not waiting until a part fails can save you hundreds, depending on the part and what else depends on it working well.

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