Timing Belts...Ignore at Your Own Peril!

[minir]

Hi to All

Very important information for those whose Vehicles use Timing Belts.
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By Jim Kerr

Routine vehicle maintenance is often thought of as simply changing the oil and checking the tires. Even annual tune-ups are often forgotten until the vehicle starts to act up. But there is one thing that is part of routine maintenance that should never be overlooked: it's the engine timing belt. Forget about it, and it could cost you a new engine.

Not all engines use a timing belt. Some drive the camshaft with a chain. Chain drives are more expensive to build, but often last the life of the engine. They are also narrower than a timing belt, so there is a tendency to now use chains more than belts to enable more compact engine designs for tight engine compartments. How do you know if your engine has a belt or a chain? It may be difficult to tell by looking, so the best way is to check the owner's manual maintenance schedule.

I have never seen a recommendation for changing a timing chain at specified intervals. A chain will start to make noise long before it will do any damage to the engine. Belts on the other hand, can be working merrily away and all of a sudden - bang! – you're walking.

Engines with timing belts will have a scheduled change interval in the maintenance schedule. Most newer engines need them changed every 100,000 km. Some will recommend changing them at 160,000 km, but there are some that need inspection, adjustment and possibly changing as low as 50,000 km. Don't guess. Check the owner's manual or the with the service department of a local dealership.

Usually belts don't break. The teeth on the inside of the belt that meshes with the sprockets come off. The camshaft stops turning but the crankshaft doesn't. Pistons come up and hit the open valves, perhaps costing you an entire engine.

Most current engines are not free-spinning. The need to reduce exhaust emissions has forced engine designers to eliminate the recesses in pistons that would allow the piston to move to the top of its stroke without hitting an open valve. These recesses trapped pockets of unburned fuel, creating more emissions. Non free-spinning engines will bend the valves every time if the crankshaft is turned without turning the camshaft at the correct time.

Changing a timing belt usually isn't hard but can be time consuming. However, do it wrong and you will be looking at major engine repairs. Usually there are timing marks on the crankshaft sprocket and the camshaft drive sprocket or sprockets. These marks are aligned in relation to the block and cylinder head. When the marks are lined up, number 1 piston will be at top dead centre of its stroke.

After removing parts such as the crankshaft pulley, engine covers and sometimes an engine mount, the timing belt tensioning mechanism is released so the belt can be slipped off the sprockets. A new belt is installed and the correct tension set on the belt. Too tight and it will "sing" or make a whining noise. Too loose and it may slip. Check that the timing marks are still aligned, and before putting it back together, rotate the crankshaft two full turns in the direction of engine rotation and check those marks again. If a sprocket is out of time by one tooth, the engine will run but be low on power. Two teeth out and it will usually run but roughly. Three teeth out or more and you may bend a valve.

After a belt has failed, usually a new belt is installed and then a compression test is done on the engine. Cylinders with low compression will likely have a bent valve, requiring the cylinder head to be removed and repaired. It is much easier to replace a timing belt before it fails than to replace the belt and valves after it fails.

Sometimes a timing belt will need changing before the specified mileage interval. Oil or antifreeze leaking onto the belt will break it down. Don't take a chance on it. Repair the leaks and replace the timing belt. Always use a high quality belt. Cheap belts may look the same but the inner construction is much weaker. Use quality brand name belts from the aftermarket or get an original one from your dealer.

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regards

minir

[CoolJ]

Good read Minir!

My buddy needed his replaced. But he kept putting it off and spending money and performance mods. After a month his chain took a dump and he needed the motor rebuilt.

[minir]

Good Morning CoolJ

Thanks CoolJ. I do think that the Manufacturers should put more emphasise on the need to replace these items on a regular basis CoolJ. They of course are hesitant to do so as it may negatively impact their Sales of the Vehicles to start with. The offshoot is many people are unaware of this situation and it can be very costly to find out the hard way.

Vehicles are so reliable today, many people simply fail to follow the Recommended Service Intervals and ignorance is not always Bliss.

I too thought it a worthy read and hopefully may save someone a bit of expense.

Thanks CoolJ and do have a pleasant day

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regards

minir

[nepenthe]

I know this all too well, Larry.

[blebs]

Personally I think they should leave belts for driving accessories, not critical engone components such as the crank and camshafts! I see no reason why they cannot use chains. Sure they may have to do some engine redesigning, but belts for this purpose are not a good thing.

[minir]

I know this all too well, Larry.

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Good Morning nepenthe & blebs

nepenthe
Ouch!

i recall now your problems with the Audi. A shame this article didn't appear prior to that situation arising.

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blebs
When i was in the Industrial Bearing Business, Timing belts were just coming in and where an excellent choice for many applications. Quiet, maintenance free, etc. Most however where not internally used.

I think and i may well be wrong here, but i seem to recall the Oldsmobile Tornado being a first adopter for Car use.

Chains have their limitations as well. They wear the Sprockets and themselves over time and will stretch and weaken also. They can also be noisy in going about the business at hand. However as mentioned, usually the extra noise generated will tip you off to something going wrong prior to catastrophe. Though not always.


Nothing however replaces a good Mechanic and regular Servicing imho. One being had to find and costly when you do. A Fella can't win anymore it seems. Damned if you Don't & Damned if you Do!

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Thanks Fellas and i hope your day goes well

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regards

Larry

[YeOldeStonecat]

Yup...especially important with "interference" designed engines. Ex-wife had a Honda Civic, it blew the timing belt, so the valves and piston tops collided. Needed a complete engine rebuilt. Her next car was a Subaru, non-interference design, naturally she blew that timing belt also...but the car coasted to an easy stop, no damage to the engine.

[minir]

Hi YeOldeStonecat

Sounds like the X was a diaster when it came to Cars YOSC

You just have to love Subaru's

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Do have a dandy day and Thanks for your reply

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regards

minir

[brembo]

I managed to pop a newish timing-belt on my Integra, thankfully it was a non-interference engine. I had that engine at the bleeding edge of tune and it just didn't like the revs I'd generate I guess. It broke while at a light idiling, just outta nowhere. I yanked the oil cap, wiped a cam lobe down and cranked the engine...didn't move the cams, so I knew right then and there that the timing belt was broken.

BTW, on Japanese cars it is a MAJOR PITA to change em. My hands are too big for most of the work on the things, that is why I have a tuner now. I let Dale do all the dirty work under the WRXs hood nowadays.

[minir]

Hi brembo

Glad it was too costly brembo. They can and do let go at strange times and with out warning. I loved the Belting Business back then. Very lucrative.

Thanks and do enjoy a pleasant day

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regards

Larry

[triniwasp]

That's why I love my Nissans, they have timing chains . Don't know about the new ones though. I 've had a 92, 95, and now a 98.

[minir]

Hi triniwasp

Nissan makes a good product. I loves the 350Z

Thanks and have a delightful day

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regards

minir

[Loonatic]

Good thing my L67 (3800 S/C) has a timing chain. They usually last a long time.

However. when I cam my car or install 1.9 ratio rocker arms, I would stretch the stock timing chain so Id need a double rollermaster timing chain. Beats a belt any day, IMO.

[Zilog B]

That's why I love my Nissans, they have timing chains . Don't know about the new ones though. I 've had a 92, 95, and now a 98.

Yep, my 93 nissan truck has a timing chain instead of a belt. Not that I do any maintenance besides add gas and change the oil tho

[minir]

Hi Loonatic & Zilog B

Looks like you've both lucked out on chains. lets hope they last forever

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Thanks and have a terrific evening

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regards

minir