Belt age versus belt mileage


I have a '99 Subaru Outback wagon with 53,800 miles. Car is driven less than 5,000 miles per year, always garaged, all maintenance done on-time. The Subaru maintenance book says the TIMING BELT should be replaced at the 105,000 mile point, or 105 months of age. My car is past the “age” point by a few months, but with mileage that is only HALF of the suggested mileage for changing this item I would appreciate your take on the “Belt age versus belt mileage” question.



Old belt, new belts…

The Subaru maintenance book is correct on miles and age. We’re talking 10 model years here. Even ten year-old tires go beyond being safe because of cracking and age.

It is now time for a new timing belt.

The same story would apply if one puts on 105,000 miles in only 52 1/2 months. It is which ever occurs first.

We have had this post MANY TIMES. Belts are made of rubber and rubber desteriorates with age as well as with use, especially if in contact with oil. So I would replace it and the water pump as well if it is driven by the timing belt.

We have had many posts of broken timing belts and very expensive repairs. If your car was under the FAA, which regulates aiplanes, you would be legally required to change it!

Subarus are very good cars and in the hands of those who do regular maintenance they have very long and trouble-free lives!

More belts…

In addition to the timing belt and water pump, I would replace all other belts, serpentine or accessory, that have not already been replaced. Replacing these other belt(s) gives you a big bang for your buck. Their relatively inexpensive cost can keep you safer and possibly prevent a break down, leaving you stranded.

It is which ever comes first. Sort of like a ice cream cone. 30 licks or 30 minutes, ether way and you have no more ice cream.

Replace the belt.

Read the maintenance schedule again. I am quite sure that while it says “105,000 miles or 105 months”, the implication (if not the explicit statement) is “whichever comes first”–and the elapsed time factor has now come and passed.

The maintenance schedule is written by the people who designed and built your car, and their goal is for you to be satisfied with the car. When (NOT if) the best snaps, you will not be happy, due to the VERY high cost of repairs.

If you have the belt (and the water pump) replaced now, proactively, it will cost you…probably something on the order of $500.–$600. If you wait until the belt snaps, the repair cost will be something on the order of $1,500.----$2,000. plus the cost of the belt and the water pump. I know which option I would choose, but your values may be different than mine.

Maintenance almost always costs less than the repairs that result from lack of proper maintenance. I urge you to have the belt and the water pump replaced a.s.a.p.

I had a similar situation with my Acura. The car had about 60K miles, but was more than seven years old, which is the time Acura suggests replacing the belt.

Since I’m well aware of the damage caused by a broken timing belt (and consequent repair expenses), I chose to have the belt replaced, rather than gamble on it.

If your timing belt breaks, the cost to repair your engine will be MANY times the cost of the timing belt replacement. I suggest you make an appointment to have the timing belt replaced (might as well do the water pump at the same time), and then you can relax and stop worrying about timing belt failure.

I’m going to be contrary to popular opinion here. The time factor could be extended depending on where you live and how you drove the car. If you live in the northern US and drove mostly or all at highway speeds, then the heat aging temperature and time that the belt was exposed to will be less than it would be if you lived in the southern US and drove mostly at low speeds. Low speeds would, of course, cause the engine to be hot for longer. An engine in the south will heat up faster and cool down slower. Belts can heat age even if the engine is not running due to residual engine heat.

Rubber kept at an elevated temperature over time deteriorates (hardens). My timing belts in another brand show little or no wear at 60,000 miles when I change them but there is some concern about invisible fatigue of the reinforcement fiberglass due to mileage accumulation. Rubber at room temperature changes extremely little to none at all.

The problem is that we don’t have access to belt failure data that can help to make an informed decision as to how long the time factor can be increased or decreased with varying vehicle usage time at reduced mileage. This type of information could be made available but someone would certainly misinterpret it. In the case of a used car, you might not reliably know how the previous owner used it.

The simple and safe answer is to change the belt. Every 105 months gives you plenty of time to save up for that task. If you live in the far north and drove the 5000 miles per year at highway speeds, then you could risk a little more time.

Looking at a timing belt will seldom provide any useful information. Most bets are going to look fine the day before they break.

Why waste your money on “on-time” maintenance and then skip one of the three important factors to a cars life operating at reasonable expense:

  1. timely oil changes
  2. timely coolant changes/inspections
  3. timing belts

I also disagree with the majority opinion, depending upon whether you have an interference engine or not and whether you are willing to put up with some inconvenience and risk.

If you have a NON-interference engine, the engine will just stop suddenly if the belt brakes. This could be a safety issue or maybe you’ll just glide to a stop. No damage will be done to the engine and you can have the belt replaced then. Of course it could be a cold dark night in the middle of nowhere, or while you’re trying to pass a truck on a two-lane road with oncoming traffic.

If you have an INTERFERENCE engine, you should change the belt. If the belt breaks the engine will be toast.