If you've ever run your timing belt until it broke, how many miles did you get out of it? (Please specify TURBO or NON.)

I've been wondering whether the change interval is too conservative, considering that all the 240 series engines are non-interference.

Doug Harvey

The timing belt durability has little to do with miles, but a lot to do with TIME.

WHat I mean is, you could probably put a new belt in and drive 150k with it, if the miles were quickly put on, and on the highway.

But, you could break one at 55k if you meandered around the city for ten or twelve years.

It is more a function of age and old, creaky tensioners, dried out belts, etc., than it is purely a function of miles. This is one question where you will get a variety of answers, all of them probably "right".
--
Chris Herbst, in Wisconsin.

I try to do my belt changes on time (50K), but I've seen plenty of cars with unknown histories go much more. A friend just bought a '93 245, as best we could decipher the faded sticker that t-belt's been in there for nearly 70K. Some of his cars are on the "yeah, we should get around to doing that soon" maintenance plan.
A 360 of another friend was more a case of "you just bought it, the PO put 80K on it and didn't, and it didn't have any recent maintenance when _he_ bought it? Better change it, and the tensioner too". Tensioners I remove and spin by hand, if they're noisy they get changed, if not they're probably good for another 50K, Waterpumps I spin by hand, if they're noisy or don't run smooth again change, if not again they can stay. Lets face it, either a waterpump or a tensioner can be changed in-situ without removing the timing belt.

While we're doing a survey, have others who maintain a relatively large number of cars (I'm doing 3 of my own, and about another 9 for friends and the occasional bit of trade) noticed that jobs tend to come in batches? For a year or so it seemed that half the repairs I did was changing exhaust, by the end of this month I'll have done 5 timing belts in 3 months, last spring it was rear brakes...

Bram

I always do mine at 50,000. It gives you a chance to check the tensioner bearings, and watch for oil leaks from the camshaft seal, and anything else that may catch the eye.
Also I'd rather avoid a breakdown at dead of night or in the rain if I can.
It always seems to me that the engine runs a shade quieter after I have just done the belt. But possibly that is just imagination.

Doug,

Broke original timing belt on '80 DL at 75K. I had been putting it off until I forgot about it, then had to get it towed. The additional cost prompted me to change it at 50K intervals from then on.

Last time I changed it at 275K and found I saved myself from another roadside repair job - one of the interior timing belt housing bolts had backed out and caught the belt chewing it up pretty significantly. It was getting ready to break. (I found the bolt resting in the bottom of the housing in the typical accumulation of goo). So, something else to think about...

Chuck2

I change mine every 50K miles. every other change gets new seals,tensioner & waterpump.Just did mine this fall at 150K-new seals,next time new waterpump & tensioner.After installation drive for 15 minutes & re-adjust tensioner.Then after 600 miles re-adjust tensioner,then do re-adjustment every 10K miles.After 50K belt still looks decent but it could be stretched somewhat.Could stretch it to 55K but my present method provides mucho peace of mind.After all whats the worst that could happen doing it my way?

On an '83 GL B23F, the timing belt broke at 118k miles. I bought the car from the original owner. He said, "Sure I replaced the timing belt, the one with teeth, right?"

"In fact, I replaced them both."

The alternator belts, duh.

First, if you religiously "retension" the belt -- not once, but every 10k-20k miles, then you can probably get an easy 150k from the belt, maybe more.

Second, whether or not it's an interference engine, it's still a royal pain in the ass when the belt breaks 100 miles from civilization at midnight on Sunday with wife 'n kids in the car and no cell phone. And it's pouring rain outside at 32.1 degrees.

And no raincoat or boots.

I believe that timing belts break not because they wear out, but because they stretch slightly to the point that the teeth in the belt finally disengage with the cogs in the sprockets and ride over the cogs. The resulting extreme tension snaps the belt.

If you "retension" frequently, then the increased length (stretching) of the belt is always accommodated, so the belt and sprockets never disengage.

That said, I replace mine like clockwork at every 50k anniversary on the odo.

And I "retension" at about 25k and at 35-40k if the weather's good.
--
Don Foster (near Cape Cod, MA)

1988 DL - first belt went 8 years to 105,000 before changing. Didn't know I was supposed to have it changed (didn't read owners manual I suppose) and dealer / mechanic was 1 hour away and not in the direction we normally went. Did not break. I bought the car new.

'85 240 n/a

Got seven years and 60K miles of service from the original belt, and no, it wasn't oil soaked. I suspect that it failed as a function of age, and that the folks who are getting in excess of 100K miles of service from their belts log 25K+ miles a year.

The lowest "broke" mileage I can confirm was about 68K miles.... pretty sure that one was oil-soaked too.

MAny many of them over 100K.

Known breakage at 114K.

Don't know of ANY of the new style (round teeth) that I ever saw broken... but they also are just in newer cars and perhaps they have just not had the history yet.... though now are hitting the 10-year mark and anything's possible.

Oil leakage from cam or crank seal drastically shortens life of both the t-belt and the waterpump seals.
--
Rob Bareiss, New London CT ::: 86 244DL, 87 244DL, 88 744GLE, 91 244: 808K total

I change the T-belts on my cars around the 60 K mark, with the tensioner on every other one. May be conservative, but it's an eight hour drive between Fairbanks and Anchorage and waiting for the tow truck gets real old at -40 F.

It's not the cost of the belt or tensioner, it's the not knowing where it will let go. So I try to do the maintenance on schedule just for the peace of mind.

Conservative, perhaps. They have to be, because of the liability should it have failed at 49,900 miles instead of 50,000. And even though it's a non-interference design, why take the chance? It's a $10 belt, and I can change it in about an hour. I wouldn't want to be stranded somewhere because I decided to eek a few extra miles on it.

-- Kane ... who has heard of 'em going over 100k on a N/A, though. Still not recommend, mind you.
--
Blossom II - '91 745Ti/M46 ... Bubbles - '74 144GL/BW35 ... Buttercup - '86 245GL/AW70 ... The Wayback Machine - '64 P220/M40

I change 'em every 40,000 mi or so. However, I've never taken one out which looked like it was ready to fail. Also, I loosen the tensioner and let it take up stretch (slack) a couple of times a year; this takes 2-5 minutes to do.
1984 1/2 244GLT (Turbo) Ca. 145,000 mi.
JMS
Denver

Well our 240gl with 290,000 milege on it.. last time we change it at 200,000 ago so now we have gone 90,000 extra without doing any thing to it..

I want to change it now.. but have to pull out all belt and stuff it scare me a bit... still look into it...

why we have not replace it ?? dealer told us 200,000 mg ago that the car it stand on it last leg... and not worth any thing will die any day to our suppri it still runing...