HELP! Timing Belt Paranoia

rkornegay · May 2003

I have a '99 Mitsubishi Galant V6 with 70,000 miles on it. The manual recommends changing the timing belt at 60,000 miles, but I haven't had it done yet. My cousin recently messed his engine up with a broken belt, which got me thinking about my car.

I'm just recovering from a job layoff, so I just can't afford to get the belt changed until around the end of next month. But every time I drive my car, I'm fearful that the trip might be the fateful one that my belt breaks. Am I overreacting?

Do Mitsus have good belt durability? I'm hoping to last one more month.

Any help would be greatly appreciated.

Mr_Shiftright · May 2003

You are asking us to predict the future...no can do.

Sure it's a risk. Probably the odds are best for you at 61K and get progressively worse.

The best I could say that if it happened within the next month of driving, you'd have fairly bad luck going for you. I'm sure many people get away with it, but there's no way to know where you are going to land on the bell curve of probabilities, is the problem.

tmt1961 · May 2003

i also have galant 97 with 90k with original timing belt. to have a peace of mind you can open up the plastic cover the timing belt to see the condition of the belt and make a decision.

Mr_Shiftright · May 2003

Good idea-- but not easy to spot anything except a huge defect. Still, as you say, some peace of mind there....

swschrad · May 2003

oil rots timing belts... any leakage means a front seal is going out, needs to be replaced as well as the timing belt.

but if all you have is some dust, a little rubber or fabric debris, and you don't see the belt chunked out, it's OK.... now.

I replaced the belts in my ranger 2.3L-four religiously every 50-thousand miles or thereabouts. just to have it done. course, I was working, and it does make a difference on how much preventative maintenance you can afford.

Mr_Shiftright · May 2003

My friend had some bad luck...her BMW manual said 60K miles for a new belt, and hers let loose at 61.5K. Unusual, but there you go.

andre1969 · May 2003

is an interference engine, so if the belt does break, you do run the risk of doing some serious damage to the engine.

I dunno about the quality of the belt, though. It's only as good as the manufacturer who won the low bid on that contract made it to be!

As for belts in general, I've only had one car that had a timing belt...an '88 Chrysler LeBaron turbo coupe. It called for changes every 60K miles, but we let it go to 90K before a change. It needed new seals, too...crankshaft and camshaft, because it was leaking a bit of oil. The 2.2 was a non-interference engine though, meaning that if the belt failed, it only stranded you, and didn't demolish the engine. Still a bad thing if you're doing 80 in the fast lane in heavy traffic, though!

swschrad · May 2003

I had a timing chain finish rounding off the points on the cam gear (GM nylon gearset, thanks for asking) when I was decelerating a 76 buick into a rest stop long years ago. didn't know the difference until it wouldn't start when I was ready to go. blew real pretty smoke rings when I took the air cleaner off... but that's not the job of the carburetor. when I got the old cam gear, it was not only worn down to the little steel nubs, but they were rounded off, too.

if you have an interference engine, you have a different experience when the belt slips or breaks. you hear a loud THUNK! and start sliding on locked tires. that engine won't turn again until major repairs or replacement is done.

andre1969 · May 2003

really? Does the whole engine actually lock up like that? Sounds like it would be one heck of an experience! I thought the crankshaft would still keep revving, but the camshaft would stop and let the valves get smashed.

Aren't most older V-8's and V-6'es interference engines?

The only time I actually got to see a timing belt go bad was on a VW Fox. Last year, I was renting to someone who was turning out to be a real pain, so I kicked him out. On the last weekend he was going to be there, he parked his car, and when he went to start it it wouldn't start. Perfect timing, eh? Turns out it was the timing belt. Non-interference engine, thankfully. He replaced the belt himself (mostly...I helped him a little bit...I wanted that sucker GONE!!) I remember the way it failed...the little "teeth" were actually falling off the belt, but the outer part of it was fine.

He put a new belt in that cost about $10.00. I don't remember if the oil seals were leaking or not, but he didn't bother to replace them. I have a feeling that his little repair isn't going to last forever.

I'll also admit that I was a little envious that the little #$%! was able to do a repair like that. I don't think I would've had the guts to take on something like that myself! But then it took him about 2 days to do it, and if you could see the way his hands and knuckles were bruised up, and the words that were coming out of his mouth...

nippononly · May 2003

I will take a car with a timing chain any day - the chain may be a little noisier, but much more durable and gives you plenty of warning before it breaks.

cutehumor · May 2003

I have a 92 mit mirage with 111k miles on it. the timing belt was changed by previous owner at 51k miles in 1997. it's been six years and 60k miles. I'm tryin to push for a change till 125k miles so I only have to do it once. Plan to keep car till 200k miles. It is interference engine however. I'm going to pry the timing belt cover to see if the belt has any cracks. My v ribbed serpentine belt has some cracks and I don't think it has been changed in the car's 11 year history. will replace at the same time.

swschrad · May 2003

each keeps the other from moving. an interference engine gets that name because the designers, to squeeze the last little energy possible out in a small space, have the valve travel overlapping the piston travel when the parts are supposed to be far away from each other.

since two items are not able to occupy the same space at the same time, when they come together under force of dozens or hundreds of horsepower (action/reaction, the entire chain of rotating parts will expend all its power against the greatest restriction,) things get bent and broken real fast. as the valves are going down while the pistons are going up, and both have to finish their travel before they reverse direction, they mung each other up pretty good.

I helped a work buddy fix his beater Chevette a few years ago on a moderately warm February weekend (20 degrees), and his timing belt had not only shed a couple inches worth of teeth due to oil rot, the belt was separated into several sections. learned a lot and passed a little on that day, as well... some of which was the timing marks were not right on the engine, the camshaft was 180 degrees off, so somebody had shade-treed that thing before and got the cam gear on wrong. just humped the cam over two thunks and it took right off after I slid the belt back on.

doesn't work like that with an interference engine... we would have had to do a valve replacement for sure, even turning it over by hand, and almost certainly the top of the piston would have been damaged, with the drill being to replace the piston at that point and check all the other running parts and the crank bearings before assuming anything about being able to fix the alignment and try again.

it would be a good idea to check. the belt tables at

http://www.gates.com/brochure.cfm?brochure=981&location_id=54- 0

will mark interference engines with a star. if you're there, and you have to ask questions, have a shop do it.

ziegman · May 2003

it just never ceases to amaze me how many people try to push the timing belt. why? you gain nothing from putting it off and only risk locking the engine up. i understand people trying to figure when is a good time but if you have the money, do it. it will save you lots of trouble and money down the road. i have a friend who drove his car till the timing belt broke and he has had nothing but problems with the engine sense then.

swschrad · May 2003

and while job searching had this milestone come up. been there, hated it, I feel for him. I have had one interference engine, primarily because I didn't spend enough time researching it before purchase. but I got excellent service from it.

not that I am morally and socially agahst at the thought of somebody zooming past me on the road and cutting in quickly, mind you... but it ain't me and I like my stuff solid and engineered to last darn near forever.

pushrods that have a better torque curve for towing are more my style. there's still something in the market for me, and I'm happy.

but if anybody does have a spare zoomie convertible I can have for summers that doesn't need work, let me know

andre1969 · May 2003

...thanks for the detail, but wouldn't the crankshaft be strong enough to make the pistons just smash the valves out of the way, and keep on revving until it slowly died down? At least that's always the mental picture I got. I knew the valves would be shot and the pistons damaged, but just didn't know about the part where the engine would lock up!

Not that I want to experience it first-hand anytime soon!

Also, did older engines used to handle it better when the timing chain broke? It just seems like, in the past, I didn't hear about timing failures totally destroying the engine like they do today. Maybe a valve here and there, but not the whole system!

nippononly · May 2003

a timing belt break only destroys interference engines, which the majority of engines (Honda excepted) are not.

If the t-belt breaks in a non-interference engine, you just have to react quickly to coast to the side of the road, as it will stop running.

For a couple of hundred bucks, I usually also wait until the timing belt is due (per manufacturer specs) before changing it...but I don't try to extend it a whole lot.

I am really glad they are mostly going back to using chains. Timing belts are a needless annoyance.

andre1969 · May 2003

how long the typical lifespan is on a timing chain? People used to say they lasted forever, but that was back when, by the time a car had 100-150K miles on it, it was either old and ragged out, or was several design cycles old and out of fashion, so nobody wanted it anymore.

I'd imagine for people who have kept a car 300-400K miles or more, there's a chance they would have gone through a timing chain or two, isn't there? Years ago, I found a '72 Impala 'vert with a 350 that I wanted to buy. My neighbor, who's a real Chevy head, warned me that at around 125-150K miles, 350's of that era usually needed a new timing chain.

Timing chains are probably just like everything else...once upon a time they were over-engineered to the point you rarely had to worry about them, but with fuel concerns and such, they had to make them lighter and more fragile in more recent times. Of course, technology has allowed them to make them more durable, but then that still gets offset by the need to make them lighter, so it's a draw, more or less.

nippononly · May 2003

(1) chains give you some warning when they are near to giving up the ghost, and

(2) even if the change interval is 150K (I have never had to change one on old Toyotas I have had, but say for the sake of argumant), that is still longer than any belt would go, and the price is almost the same to change it when that time comes (chain costs a little more, labor is the same)

swschrad · May 2003

and you coast to a stop. at least, mine did. the chains usually don't break unless you have oil pressure issues that starve them, but the gears get worn out.

I suspect, not having done any teardown or destructive testing on an interference engine, is that you either shred the belt and you keep moving valves, although with increasing synchronism problems, until metal on metal stops it... or the belt snaps, and intertia will carry the cam around one more time, until metal on metal stops it.

remember, you are going to bend over valves like badly hit nails, and possibly punch through the tops of a piston or two, worst case being the belt fails under acceleration. if you have a bad pin or rod, it might snap and the engine roll a few more degrees until the next cylinder gets it.

but I don't think you're going to be able to turn it over with a wrench and a 30-plus sized mm socket by hand after an interference timing belt gives out any time before the heads come off.

corancher · May 2003

Quite some time ago I had two experiences with stripped timing belts on an interference engine. They were not my fault, as the first one happened at 22,000 miles (well short of the 35,000 mile recommended change interval) and the second one happened at 70,000 miles--9 months and 8000 miles after the belt had last been changed. It may not surprise you to learn that the vehicle was a Fiat.

Anyway, the engine didn't hang or bind, and could afterward be turned easily with the starter or a wrench. The camshaft stopped turning while the engine was at idle and there was no drama or sound at all. The engine just died. All 4 exhaust valves were bent, requiring a rebuild of the head. The pistons were not damaged at all. One mechanic said I could have been unlucky enough to have it happen at high revs, but that was unusual. Stresses on the belt were actually worse at idle.

Belts today are a lot better, but can still break or (more likely) strip teeth.

Speaking of teeth, one thing I learned from the 2nd failure was to closely inspect the teeth on the crank and cam pulleys. They can wear and cause a very premature belt failure.

isellhondas · May 2003

Do not give warnings before failure except in rare cases!

Andre, not to scare you, but I remember Pontiacs as being one of the worst on timing gears. The plastic tipped gears wear out after about 70,000 miles as I recall. The replacement gears don't have the plastic and rarely go bad.

Trouble is, the plastic breaks off and gets into the oil pan where they can plug up the oil pickup.

If your Catalina has over 100,000 miles, it's *probably* been replaced at some point.

swschrad · May 2003

the drive gear for timing was made a nylon job over a steel hub and gear bracing sometime in the 1970s for quieter operation, I was told. I got 128,000 in my buick V6 before one tooth finally wore enough to let the chain jump a dozen or so links coasting into a rest stop one frozen night.

with the all-steel replacement timing set installed a day later, I didn't notice any extra noise. but having changed something inconvenient, I was suddenly noticing every other little wobble, squeak, and hiccup the car exhibited, and probably had for months or years.

two months of that, I was in a new ranger pickup.

andre1969 · May 2003

yeah Isell, I've heard that too, about Pontiacs. My Catalina has a rebuilt 400 in it though, that probably had less than 1,000 miles on it when I bought it (y'know, the old cliche about "It's so clean you could eat off it!"). I've probably put another 10K miles on it since then, so at the rate I'm going, it'll probably outlive me! Hopefully, when the engine was rebuilt, they did something with that timing gear!!

Years ago, I knew a guy with a late 60's Olds Delta 88. I think it had the nylon mesh thing. Anyway, it ended up going bad, and did a good little number on the engine. And my '82 Cutlass Supreme 231 decided to lose all oil pressure one day. When we pulled the pump gears out (real easy on a 231 'cuz they're in front...no need to drop the oil pan), they were all chewed up and there were little metal bits in the oil. I just thought it was the engine in general self-destructing, but someone mentioned it was probably the mesh gear. Funny thing was, when I bought that car, one of my supervisors, an aerospace engineer, predicted that it would go bad between 70-90K miles. He'd had an early 80's Bonneville 231 that did the same thing. Sure enough, mine did it at 73K miles! I hate it when my boss is right!

cutehumor · May 2003

is highway miles easier on a timing belt than city miles? thus explaining why some with the 60k required interval have reached to 90k and "claim" the belt was like new.

andre1969 · May 2003

Someone posted in one of these boards awhile back (was it this one? I'm too lazy right now to look back ;-) that the belt is actually under more of a load at lower rpms. Seems to me though, that even if a higher rpm isn't as stressful on the belt, it would be on the engine if that belt broke!

I think the 60K estimate is mainly a CYA type of thing. Most of them *won't* fail at 60K miles, but at some point beyond that. A select few will fail before that, but hopefully not enough to cause any bad publicity.

We had the belt changed in my '88 LeBaron at 90K miles, and it called for 60K intervals. That car had a mix of city and highway miles.

HELP! Timing Belt Paranoia

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