timing belt or timing chain?

To this day, most of the domestics still use a timing chain, and rarely does one ever think about them. A few of the DOHC engines (like the 3.2L and

3.5L in the Dodge Intrepids of the last dozen or so years) used a timing belt.

Imports much more frequently have used a belt. It allows (supposedly) for smoother, quieter operation and better fuel economy for the set-up. But of course, any belt is a maintenance item, and since many of those engines are "interference" engines, meaning if the belt breaks, you bend or break some things in the engine (valves, etc.), you best not forget about it.

Something to ponder when you are deciding which vehicle to buy. (All Santa Fe engines for sure would have timing belts).

Green Valley Giant

The Mazda 2.3 DOHC engine has a timing chain, which by itself is good. It also has something called "Variable Valve Timing", which sounds to me like a failure waiting to happen.

I'd say most domestic V-6 and V-8 engines have timing chains, but most of the domestic I-4's, which by and large are based on foreign design, use timing belts.

Not as much of an eminent failure as you might think. Variable Valve Timing (in different forms) exists in a lot of engines these days. Most manufacturers either have a form of VVT or are experimenting with it. Some of the stuff that's being toyed with is quite radical for your basic internal combustion engine. It's not inconceivable that the camshaft will become a thing of the past, giving way to the ever-present computer, which will monitor and adjust valve timing.

My 2006 Sonata with the 2.4L engine has a timing chain, if the web site is correct. I think the new 3.3L V-6 has a chain also, but I'm less sure on that one.

Matt

So do the new Hyundai engines. Time will tell...

Matt

And I will add that I am very pleased with the results. My new Alantra scoots much better than my Accent ever did. The VVT seems to broaden the torque curve quite a bit.

nothermark

My first introduction to a timing belt was when the one on my mid-80s Escort broke. It was painful!

Although Gilmer (that's its real name!) timing belts seem to be a rather new innovation, they've been used for many decades. That being said, however, timing chains were generally used by most manufacturers before the shift to Gilmer timing belts.

Most OHV engine designs used timing chains (most USA manufacturers) or timing gears (many European manufacturers). Actually, timing gears are the best, but can be costly to design and manufacture.

In most OHC designs, timing chains were historically used. For example, the classic Jaguar DOHC inline 3.8L and 4.2L six used timing chains, as well as most other European cars including the SAAB SOHC and DOHC inline four. FIAT used Gilmer belts in their 124 series in the '60s. Mercedes and Porsche used, and still use, timing chains.

Timing chains are more durable than the Gilmer belt. The generally accepted design spec for replacement of the Gilmer belt is 50,000 to

100,000 miles. Hyundai specifies replacement of the belt at 60,000. On the other hand, a timing chain - either simlex or duplex - can last much, much longer. The primary problem with a timing chain design over time and mileage is chain stretch. This natural wear is compensated by a timing chain tensioner, either oil pressure or mechanically operated.

One of the primary reasons for the original shift from a timing chain to the Gilmer belt is one of economics. Although the timing chain is more durable than the Gilmer belt, it's generally much more expensive to replace on an OHC engine than a belt. Not only is the timing chain itself more expensive ($50 to $200), the replacement (labor) can be very costly. In some OHC designs which use a timing chain, the engine has to be pulled to effect the repair. Whereas the Gilmer timing belt is inexpensive ($20 to $50) to purchase, and the replacement cost is much less than a timing chain. NOTE: Although we Hyundai owners may complain about this fact, it's nevertheless much less than a timing chain replacement.

Timing chain replacement in the classic American OHV engine design is also quite inexpensive, both in terms of parts cost and labor. Although OHC engine designs are much more efficient, the efficiency comes at a long-term maintenance cost increase over OHV designs.

One of the reasons for the increased cost of using timing chains (beyond the cost of the parts themselves) is that a timing chain must run in an oil bath, which in the case of automotive engines, is generally the sump. That means that it must also have an oil-tight cover over it.

Timing belts run dry and need nothing more than a cheap plastic cover to keep out dust, dirt and moisture.

And then there is my Fort Taurus SHO. Timing belt placement is such that one the case is opened it is better to replace water pump, front seal, Crank sensor and a host of other stuff as the labor charge is monumental. Lucky it's a non-interference engine.

Thanks for all the responses. All the information has been helpful. I get the opinion that the difference in having a timing belt over a timing chain is that the belt is less expensive...for the part as well as the installation. Having the belt replaced at 60k miles should be considered routine long term maintenance.

Don wrote: "And then there is my Fort Taurus SHO. Timing belt placement is such that one the case is opened it is better to replace water pump, front seal, Crank sensor and a host of other stuff as the labor charge is monumental. Lucky it's a non-interference engine."......

Actually, that is true with many vehicles, particularly the water pump. That is often used as the tensioner for the belt, making it something replaceable when you replace the belt with virtually no additional labor.

But those who said timing belts are cheap need to price out some of them. The Kia Sedona minivan's does not come cheaper than $110 (that I can find). That is just the part - with labor, I have one quote for $450, and I have a hunch it won't get much cheaper. That is not chump change to me.

Green Valley Giant

Rev. Tom Wenndt wrote: "The Kia Sedona minivan's does not come cheaper than $110."

The best price I've found on the Sedona timing belt is $94. Thus, it's more expensive than your usual timing belt parts cost. I imagine this is due to the V6 design, and most cost references to belts are those used in Inline 4 cylinders.

Although $450 is a significant amount of money, it's still cheaper than some timing chain replacements which require the engine to be pulled from the vehicle. This is most often the case in some of the European vehicles.

You're correct, Matt. Both the '06 Sonata engines are chain driven.

I've never done a Sedona belt, but it's the same engine as the XG, and the access in the Sedona looks even worse than the XG's.

I was quoted $225 Canadian at the Oakville Hyundai dealership?

Chris

True, but timing chains seldom require replacement.

Except that most timing chains (well, speaking for American engines - I don't have experience with European designs) will last the life of the rest of the engine. By the time the timing chain is shot, it is time for a complete overhaul anway. My Chrysler minivan had 178,000 miles on it when totaled and the engine was still running fine with all of its original internal components.

Matt