Timing belt calculus

[sengsational]

Given that many of us here keep a car for a good many years (not wanting to take a big depreciation hit very often), I thought I'd ask about timing belt replacement strategy.

Obviously if the replacement cost exceeds the value of the car, it's not advisable to do this expensive preventive maintenance, irrespective of the interval set by the manufacturer. But what would be the point at which it makes sense?

One factor in the equation would be the likelihood of failure between the current mileage and the mileage when you dispose of the car. Another factor, smaller for me, is the inconvenience of a failure. And of course the total loss of the car's value if a failure occurs (a new engine is required after a failure so probably means not worth fixing ).

I imagine that going 10% longer than the recommended miles for belt replacement has a miniscule chance of failure. Anecdotally, I've had two cars that passed 100% longer, and didn't fail. It would be nice to know about the fraction of failures on the specific engine by mileage, but I haven't found a source for that.

Usually I "self insure". Is this a case where it makes sense? My history with two other cars suggests yes, or was I just lucky?

[travelover]

Dunno, but it seems like it could also be a safety issue to just have it die suddenly and catastrophically.

[REWahoo]

https://www.youtube.com/watch?v=LBsiHCtkWPk

[ERD50]

Quote:

Originally Posted by sengsational ... Obviously if the replacement cost exceeds the value of the car, it's not advisable to do this expensive preventive maintenance...

I will disagree that this is 'obvious'. Let's say the car could be sold for $800 as is. A timing belt replacement cost $800.

Your actual real-world apples-apples option would be to sell the car for $800, and purchase a similar car for $1600, so $800 out of pocket. But now you have a car with a questionable maintenance and use record (you were probably more careful with your car than the average owner?). And if that car didn't just get a new timing belt, you're in the same boat. And if it did just get a new timing belt, it is probably an $800 car with an $800 timing belt - the same as you could have with your current , known history car!

So I'd spend the $800 on the repair, and then I'd own a $1600 value car. Roughly.

Quote:

.... Another factor, smaller for me, is the inconvenience of a failure. And of course the total loss of the car's value if a failure occurs (a new engine is required after a failure so probably means not worth fixing ).

As travelover mentioned, a sudden failure could be a safety issue. Though that could happen at any time anyhow, you are pushing it if you are over the stated time. How big a risk that is would be hard to say - the mfg would have some leeway and margin in that, so who knows?

From my reading, belts may wear and show problems, but often the damage is internal - the nylon reinforcing cords crack with age, and they cannot be inspected.

-ERD50

[braumeister]

Since I actually had one of those catastrophic (to my budget) experiences from a broken timing belt many years ago, I resolved to only buy cars with a timing chain (not a belt) from then on.

[RE2Boys]

I had a timing belt unexpectedly go in the evening while crossing a busy intersection. Disengaged the clutch and slowly coasted through the intersection.

It went at about 55K miles, owner's manual recommended replacement at 60K so it was a bit early. Fortunately, it was a non-interference engine and rear-drive Mitsubishi, so less than $300 and was back in business. Since then (1992), I've never owned another vehicle with a timing belt. In fact, when shopping used, I always factor in my offer price a timing belt replacement.

[gauss]

You need to determine first if you have what is affectionately referred to as an "Interference Engine".

If your timing belt gives up the ghost on one of these, you will have pistons and valves trying to occupy the same point in the space-time continuum. Given the momentum of the running engine or the torque available from the starter motor, you will likely end up with bent valves or broken pistons. This internal damage will then require an engine di$$asembly to repair. I believe that a1985 Honda Prelude was an example of such if memory serves.

-gauss

Sent from my LGLS751 using Early Retirement Forum mobile app

[stepford]

This would depend significantly on whether or not your have an interference engine - i.e. one in which a timing belt failure will cost catastrophic engine failure with valves slamming into pistons.

My first car with a timing belt (a Toyota MR2) fortunately possessed a non-interference engine. I drove it about 20K miles past its nominal replacement interval and had the belt fail on the freeway. Since this was a non-interference engine there was no damage, and other than the cost of towing the vehicle to the nearby shop the repair cost was the same as if I had simply had the timing belt replaced prior to failure.

The penalty for a delay in replacement under these circumstances is thus fairly small. In contrast the damage due to a valve train crash following timing belt failure in an interference engine would likely cost well more than the value of an older car to repair.

Factor this into your TB calculus accordingly.

edit: Dang, Gauss beat me to it. Serves me right for being verbose...

[aja8888]

Just don't focus on changing the belt, but remember that any one of the parts in its path can fail and take out the belt (typically, that's what happens). So when you do go to change it, make sure the kit contains EVERYTHING in the belt's path. That typically includes the water pump, tensioner, idler and other rollers. Change the serpentine belt at the same time.

Some cars require removing the front lower motor mount which typically is held on with torque to yield bolts. Those bolts should not be re-used. Techs usually re-use these. Some cars (like Hondas) require removing the vibration dampener and that has one massive torque setting on assembly. Not all dealer techs really use torque wrenches correctly (or at all).

A typical timing belt job at a dealership involves just replacing the belt. Good luck with that.

Oh, many cars now have timing chains. They stretch and wear out tensioner guides (and also throw codes for improper valve timing). Check Cadillac Northstar and certain M Benz engines for those costs to fix (thousands). These are no free lunch either, especially if the "tech" changing you oil uses the wrong stuff.

Ain't cars grand these days!

[NW-Bound]

Quote:

Originally Posted by sengsational ...Obviously if the replacement cost exceeds the value of the car...

How much does this typically cost? I have replaced the belt in my cars myself, except for the ones that used chains, so do not know.

[tps7742]

I have always had mine replaced at the recommended mileage requirement more for peace of mind than anything else. If I remember correctly they averaged around $750.00 from the dealership. I do know the price is more reasonable now than it used to be several years ago on most vehicles.

[CDRE]

When my vehicles have an "interference engine", I have the belt (and water pump) replaced at the interval recommended in the owners manual. If my vehicle does not have such an engine, I run it until the belt fails (drive local, no long trips) and then tow it to the shop.

[sengsational]

Thanks, all, for the insight.

The 3MZ engine is technically an interference engine, but it's not a "done deal" disaster with a timing belt failure. IOW, since the pistons have depressions in them, it can break and not have valves getting messed up. If the belt is installed wrong, there can be interference, so can't be called non-interference. At least that's what my research tells me.

Concerning paying $800 to keep driving a car with a market value of $800, I can see the logic of driving "the devil you know", but the reality for me isn't the $1,600 beater alternative that who knows what it's been through, but instead I'd throw in the towel and get a newish car at CarMax.

Despite having a reduced chance of catastrophic engine damage, a few things have me squarely in the replacement category now. First, the blue book came in quite a bit higher than I thought. And also, the repair came in at half what I imagined. Well, half of what I was lead to believe. My BIL said it would be over $1000, but I've got it priced out at $575 (yourmechanic), and that includes water pump and some pulleys..what ever is in the typical kit, I guess.

[NW-Bound]

Wow, $750 is a lot for a timing belt change. Perhaps my cars are a lot easier to work on than most others (I did them myself).

Three years ago, I paid to have the AC compressor, condenser, and accumulator changed on my car. It's a heck of a lot of work due to the pipe routing and location of the parts. And the parts also cost more than the timing belt. Plus, this was my RV toad, and the towbar blocked the accumulator, causing the mechanic a lot of grief, and he charged me some extra.

Total cost was $680, parts and labor, and included the cabin air filter. I just looked it up on Quicken.

[Bamaman]

Your Toyota engine requires a timing belt kit, however they can be bought at RockAuto.com for $55--for all the parts. I have no idea how long it takes to install the belt, however.

Such a small repair is certainly nothing to put off beyond a normal replacement frequency.

I suggest finding a good independent auto shop, as they'll certainly be less expensive on this job than any Toyota or Lexus dealership.

[CRLLS]

A few years back, I replaced my timing belt myself. The cost for the kit was around $125 as I recall. The kit included the water pump and the idler pulley. Something you don't want to replace 6 months later. It took 2 days to install in my driveway and another day to fix the 1-tooth-off problem the original installer (me) screwed up. In the mean time I found the bad radiator and a few other things that needed to be addressed.

I made sure that my next car had a timing chain.

[Hutch111]

I replaced my Honda timing belt earlier this year. The total cost was $900+.

[Lakedog]

Quote:

Originally Posted by braumeister ...I resolved to only buy cars with a timing chain (not a belt) from then on.

Same here - a timing chain is an important criteria to me when choosing a vehicle.

[Bamaman]

Quote:

Originally Posted by Hutch111 I replaced my Honda timing belt earlier this year. The total cost was $900+.

My family owned a couple of Honda dealerships one time. Honda dealers have never been shy about sticking it to your pocketbook on mechanical work.

But the timing belt will usually be all you'll spend on those cars in the long run.

I think that the newer Honda's have timing chains--getting rid of the belts. Mine is a SI, and it has chains.

[ExFlyBoy5]

Quote:

Originally Posted by Lakedog Same here - a timing chain is an important criteria to me when choosing a vehicle.

Yep. The most expensive routine maintenance on my Infiniti is plugs @ 110K miles.