A car question: do timing belts REALLY need to be changed?

[Ben Franz]

Had a 2000 CRV belt changed at 110,000 miles along with the water pump. The cost at the local Honda dealer was $5-600 IIRC. Seemed like a reasonable cost for preventative maintenance in a vehicle that was good for another 100K miles or more. An accident in 2008 reulted in total loss but the insurance adjuster added in 80% orf the cost to the settlement calculation. I was amazed.

[Pat Germain]

I My wife's turbocharged jetta service manual originally said 100,000 miles for the timing belt, but VW issued a revision to 60,000 miles. I guess they had a lot of failures. I'm not sure how a turbocharger would affect that, maybe it was the owners of the turbocharged cars (though 99 percent of people who own them still probably don't push them to a point it would make a difference).

Dave, what year is your wife's Jetta? I drive a 2003 turbo Jetta. I've never seen or heard anything other than the 100,000 mile belt change. Thanks.

[Ron Jones near Indy]

Is the use of a timing belt rather than a timing chain purely economic--lower price? Ken, my point on this is why do manufacturers build interference type engines? A broken timing belt or chain on one of these engines is a major problem. Why not engineer this problem out of the engine in the first place?

[Ken Fitzgerald]

Ron,

I think it has to do with overhead valves and valve placement within a head to get the most efficient placement of the fuel with respect to the spark for proper ignition to aid in improving fuel efficiency.

[Pat Germain]

Is the use of a timing belt rather than a timing chain purely economic--lower price? Ken, my point on this is why do manufacturers build interference type engines? A broken timing belt or chain on one of these engines is a major problem. Why not engineer this problem out of the engine in the first place?

The use of a belt rather than a chain isn't really an economical decision. A chain itself isn't any more expensive than a belt. And assembling the engine with a belt isn't any easier before the engine is put into the car. It's actually based on the design of the engine. And belts do have some advantages. NASCAR engines, for example, use a belt to drive the camshaft. Belts are more precise and provide dampening for the valve train.

Higher performance engines tend to be "interference" engines. They often have four valves per cylinder and are higher compression. They are built with closer tolerances. Therefore, if the belt breaks, valves and pistons are going to crash into one another.

Bikers may recall when Harley Davidson switched to belt drive back in the early 1980s. Many people were critical and believed a belt could never outperform a chain. However, HD still uses the belt-driven system and it has proved superior.

[Bob Turkovich]

Good discussion so far but you guys are missing two big reasons for going to belt vs. chain.

First, chains require lubrication. This results in the chain being enclosed underneath a sealed, structural cover on the front of the engine - usually a die cast aluminum part. You end up having a large circumference to seal - and typically that sealing surface isn't in one plane - a sealing nightmare. The OEM's look for ways to reduce seal surface area and, hence, minimize leak potential.

Second, chains are noisy - very noisy. Now you're putting that noise source in a metal box - between the engine block and the cover. The cover ends up acting like a speaker. The ringing noise can be (and has been) major customer dissatisfaction issues in the past. OEM engineers have gone as far as putting deadener patches on the inside of the cover or even going to a sandwich-type cover to reduce the noise.

Chain suppliers have been working on quiet chain designs but - when I retired two years ago - they were extremely expensive and unproven in durability.

[Pat Germain]

Oh yeah, excellent points, Bob.

I remember in the late 1970s Ford installed nylon timing chains and gears in at least some of their V8 engines to make them more quiet. Not surprisingly, those nylon parts didn't last long. Those timing chains were notorious for jumping.

[Jeff Monson]

Here's a couple more points.

Not all timing belt motors are interference engines, most toyota's, a good percentage of honda's, alot of euro's, some domestics.

Interference engines come into play when the need for more performance, and tighter tolerences are needed for an engine.

Every car maker out there (has at least one if not more) inherit timing chain motors that have major issues with the chain portion of the engine. These problems became worse with overhead valve engines, the chains are longer and require tensioners. Also variable cam timing has thrown problems into the mix.

If you own a car with a timing belt, look for the mfgs. recemmonded interval, its pay now or pay alot later in most cases.

I dont really think there is a superior way to drive the cam, neither a belt or chain are trouble free in most cases.

I see the future of auto's going to electronic actuated valves, its already in indy car technology. Just a matter of time before we see them on a daily driver.

[Jeff Monson]

Oh yeah, excellent points, Bob.

I remember in the late 1970s Ford installed nylon timing chains and gears in at least some of their V8 engines to make them more quiet. Not surprisingly, those nylon parts didn't last long. Those timing chains were notorious for jumping.

Dont forget the 2.5 gm!! They had a nylon cam gear that was pressed on, was amazing though how many miles some lasted before they needed to be swapped out. That was a tough little 4 cylinder, especially considering how many were produced.

[Ron Jones near Indy]

Very interesting discussion here. Thanks for the info.

[David Weaver]

Dave, what year is your wife's Jetta? I drive a 2003 turbo Jetta. I've never seen or heard anything other than the 100,000 mile belt change. Thanks.

Pat, it is a 2004. I got married to my wife in 2006 and took over working on her car since the VW dealer is somewhat confiscatory when they get a whiff of a few dollars.

I can't remember who the service update is from, Bentley publishing or something. They claimed their manual is the official print manual (it is a good manual, similar in quality to the honda service manual I had, and 4 or 6 times as thick as a chilton type manual).

Edit: just dug through the manual. The addendum is listed as an "editor's note", no clue what the basis for the change is. It states on the back that it is the official service manual. 4 to 6 times as thick as a chilton manual might be a conservative estimate. My manual version was printed in 2007, and the advice for the 1.8T covers all 1.8Ts back to 1999.

[Walt Nicholson]

The NADA average trade value for the car is just under $6,000. Subtract about $2,000 for rebuilt title and you are down to $4,000 minus all that is needed to put it in "average" condition. It seems that a better way to go would be to take the car, the $1,000 you are going to spend on the belt change and the other money you are going to spend on the air bag, brakes, etc. and use all of that to buy yourself a better vehicle.

[Pat Germain]

Pat, it is a 2004. I got married to my wife in 2006 and took over working on her car since the VW dealer is somewhat confiscatory when they get a whiff of a few dollars.

I can't remember who the service update is from, Bentley publishing or something. They claimed their manual is the official print manual (it is a good manual, similar in quality to the honda service manual I had, and 4 or 6 times as thick as a chilton type manual).

Edit: just dug through the manual. The addendum is listed as an "editor's note", no clue what the basis for the change is. It states on the back that it is the official service manual. 4 to 6 times as thick as a chilton manual might be a conservative estimate. My manual version was printed in 2007, and the advice for the 1.8T covers all 1.8Ts back to 1999.

Thanks. The information I have says VW modified the recommendation from 60,000 to 100,000 for changing the timing belt. My Jetta has just over 81,000 miles. So, I'm either on thin ice or good for another 20,000 miles.

[Jason Roehl]

I see the future of auto's going to electronic actuated valves, its already in indy car technology. Just a matter of time before we see them on a daily driver.

I wonder when this concept was first put to paper. I had tossed the idea around in my head about 10 years ago as I was working on a vehicle, figuring it would greatly simplify the mechanical portion of an engine. I had not previously heard of the idea, but figured someone in the automotive field would have already thought of it if it wasn't already being researched/developed.

Assuming the valves are controlled by some sort of solenoid, it would be interesting to see what additional electrical demands that puts on an alternator, as well as what sort of electromagnetic interference the solenoids would generate.

[Dan Hintz]

I thought Audi had a production vehicle that used elec. valves. I know the companies have been working on it for quite a number of years, but making it cheap enough for your average Toyota has been difficult, to say the least.