Life span of auto parts

May 24, 2007 5:10 PM

What is the REAL life span of auto spare parts compared to what the manufacturer or the auto mechanic tells you? Is there some sort of graph showing risk of failure of parts versus time out there? Specifically I am interested in Peugeot cambelt life spans. How dead am I if it fails?

(Is it something about my psychology that whenever I talk to a mechanic anywhere in the world, I feel like they are lying to my face and laughing about it later? )

Ok so my Peugeot 206 cambelt apparently is 7 years old and the manufacturer recommends replacement after 4 years. What I can't get over is how my service bill pften goes from $500 to $900 in the space of an hour. Is it something about my face?

posted by vizsla to travel & transportation (11 comments total)

It's not something about your face, it's something about the fact that you drive a Peugeot!

In many cases, it is true that a part lasts far longer than its recommended service interval. Examples can include sensors, accessory drive belts and fluids, even oil.

A timing, or cam belt, however, is not one of them. In all cases, once it does go, your engine will not run. In many cases, such as some subarus and hondas, your engine will be severely damaged by a broken timing belt.

But for reference, I once drove a Volvo that had 400,000 miles on it, and it had never had its timing belt changed, despite a recommended service interval of 90,000 miles. It finally broke at about 420,000.
posted by M.C. Lo-Carb! at 5:23 PM on May 24, 2007

It's not a diesel is it? Because if it is, expensive engine damage will almost certainly result if the timing belt breaks and the engine eats a valve.

You might want to try asking here (first result for googling "peugeot forum"); I don't have a Peugeot but I have gotten great information from enthusiast forums for several different vehicles.
posted by harkin banks at 5:56 PM on May 24, 2007

The service life of commonly replaced auto parts varies so much with driving style, driving conditions, and maintenance that most manufacturers publish fairly conservative maintenance schedules based on "worst case scenarios," so that customers aren't left standing on the side of the road routinely. If you're the kind of person who feels comfortable driving a timing belt for 7 years, it's terrific for you that yours has held up that long, because it wasn't designed to do that. Even if you're a habitual 3000 mile oil changer, and your brother-in-law owns the lube shop, you're driving on borrowed time and miles. And if your timing belt breaks at speed, it's quite likely the repair costs for the vehicle will exceed its value, at this point in its life cycle.

So, I gotta ask you one thing, vizsla:

Do ya feel lucky? Do ya?

If you don't, stick to the factory recommended maintenance schedules, pay the nice people at the cashier's window, and enjoy sleeping where you planned to sleep, every night.

If you do, throw caution to the winds, and count your money.
posted by paulsc at 6:22 PM on May 24, 2007

paulsc: "So, I gotta ask you one thing, vizsla:
Do ya feel lucky? Do ya?"

Well it says something that I have been driving it for almost double the expected replacement time doesn't it? That car repairs is a bit of a fear industry maybe?
posted by vizsla at 6:29 PM on May 24, 2007

I never have a mechanic replace anything until the car stops moving. The success of my method hinges, of course, on how comfortable you are occasionally walking down the side of the freeway.

I agree with M.C. Lo-Carb!, make sure it won’t do any damage first, but then my advice is roll the dice. Mechanics always want to replace something or other. I always figure I’ve got better things to do with my money than replace working parts on my car.
posted by BostonJake at 6:40 PM on May 24, 2007

I'm not a mechanic, but I'd be surprised if any modern, high compression ratio engine wasn't at severe risk of serious damage as a result of a broken timing belt. I'd count pretty much any 4-cyl engine in that category, and most 6's and 8's too. If the timing belt breaks, valves stay open while pistons keep moving. If a piston hits a valve it seems like it would be bad for the piston, the valve, the head, and maybe the cam.

I've let other car parts go over their service interval, but I really don't want the aftermath of a broken timing belt.
posted by Good Brain at 6:49 PM on May 24, 2007

I should add that the car has only done 40,000 km and the recommended replacement equation is 100,000km or 4 years.
posted by vizsla at 6:54 PM on May 24, 2007

I'm not a mechanic, but I'd be surprised if any modern, high compression ratio engine wasn't at severe risk of serious damage as a result of a broken timing belt. I'd count pretty much any 4-cyl engine in that category, and most 6's and 8's too. If the timing belt breaks, valves stay open while pistons keep moving. If a piston hits a valve it seems like it would be bad for the piston, the valve, the head, and maybe the cam.

Except on non-interference engines, which are designed so that a timing belt break doesn't destroy valves or pistons. Many Japanese manufacturers have been building these since the late 80's. Don't know about the Europeans.

Personally, I'd seek out a brand-specific forum and ask there. For example, I know waaaaay too much about mid-80's Toyota trucks, and I'm just a hobbyist. I imagine there are others out there with a passion for Peugeots. THEY are the ones to ask.
posted by mosk at 7:48 PM on May 24, 2007

Except on non-interference engines, which are designed so that a timing belt break doesn't destroy valves or pistons.

Except that a timing belt failure, in this case, leaves you at the side of a road.

We've got two choices in this part -- chain and belt. Chains are loud, heavy, suck power, and in the few cases where they fail, they can easily "destroy" the engine -- that is, cause enough damage that fixing it exceeds the replacement cost of the engine. However, with proper engine maintenance, they'll last forever. This, mainly, is "change the oil, doof."

Belts are quieter and more accurate, and handle higher speeds. They, however, do no last forever.

The correct answer with belts -- timing or no -- is "replace them at the suggest intervals, period." In the case of interference designs, the cavet is "or you'll destroy the engine." Even without interfering valves, you can do damage (see "spark firing with exhaust or intake valve open because belt slipped") and you will be left with an instantly not-running motor, often at high speed.

If the manual says "replace timing belt every three years/36,000 miles" you replace it when the timing belt has it's third birthday or the odo rolls to 36K.

Click and Clack rate timing belts as a class A to B problem. Class A problems leave you with a dead car. Class B problems leave you with a huge repair expense. (Class C problem kill you.)
posted by eriko at 8:45 PM on May 24, 2007

For cam belts there probably -is- a graph of the type you mention. Very early on with cam belts (Fiat used these cogged belts first, I believe) the recommended replacement interval was two years or 50,000 km. My newish Subaru's belt replacement interval is 170,000 km (105 k miles). Since the failure mode of the cam belt is usually fatigue in the reinforcing cables that run through the inside of the belt, this improvement in life is significant. The other failure mode is separation of the rubber from the core of the belt, and if you happen to have seven-year-old tires that are showing cracks, the same thing is happening to the belt.

You are at increased risk of the car's breaking down right now, and as pointed out above the breakdown will probably not be cheap to remedy. If it were my car I would change the belt tomorrow and not drive it until the work got done.
posted by jet_silver at 9:36 PM on May 24, 2007

jet_silver: "You are at increased risk of the car's breaking down right now, and as pointed out above the breakdown will probably not be cheap to remedy. If it were my car I would change the belt tomorrow and not drive it until the work got done."

Sigh. Ok. I'll get it done. I just hate auto repair shops. I don't hate mechanics as such - they're just tradesmen doing their job but the front office people really know how to suck the bucks out of you.
posted by vizsla at 11:25 PM on May 24, 2007