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What are the advantages of timing belts?

I always hear about the disadvantages of a timing belt and how it is a $300 job every few years or so, depending on miles driven. Other disadvantages include you being stranded with a non-running engine until the belt is replaced or the worst case of an essentially trashed engine from the valves crashing into the pistons or vice versa.

Are there any real advantages to these compared to timing gears or chains? Are they better for fuel economy due to a lighter mass or is there any other practical reason for them besides getting you into the shop for a replacement or worst case a new car if you neglect them?

Conor

Not In My Opinion, Not To The Car’s Owner, Although Some Will Be Offered Here, I’m Sure.

I quit buying cars with timing belts several years ago, right after I wrestled my last one into my 3.5L Intrepid V-6, out in the driveway over a couple of days, purchased and home-made special tools and all.

They’re silly, really.

CSA

This topic has been beaten to death, and the consensus is that if there is an advantage, it really isn’t worth it.

Please see http://community.cartalk.com/search?cx=partner-pub-7133054861616181%3A2yk2yg-lkla&cof=FORID%3A11&ie=ISO-8859-1&q=timing+belt+advantage&sa=Search

I think I am the only person to make a case for the advantages of a belt, and even I realize calling these items “advantages” is a stretch. In the end, the only real advantage is that replacing your water pump at the same time as the timing belt means your water pump will never get a chance to fail, and if you’re lucky, your mechanic might find and repair other items that might otherwise fail or cost you more money as a separate job, like a leaky gasket or seal inside the timing belt housing.

BTW, if you can really find someone who will do a full timing belt job for $300 (with the whole kit, not just replacing the belt), take advantage of that opportunity and thank your lucky stars. On many vehicles, timing belt jobs range from $450 (on my Civic) to $900 (on some minivans). You really should get the whole kit, which includes the tensioner pulley and sometimes other important items, depending on the model.

They’re cheaper; that’s very appealing to the car makers.

I’ve also heard some lame excuses from manufacturers that “they are quieter”. I don’t ever have heard a normal operating timing chain.
They save money in manufacturing.

I see. I have heard timing belts slapping covers before as well as chains on the early 1990’s Dodge 3.9L V6 engine commonly used in the Dakota. Those Dodge engines all clack loudly at idle and I was driving a friends to get some parts at AutoZone. The AutoZone manager told me that I had a knock like a wrist pin or rod. I told them that they all sound like this and I don’t recall many of these engines catastrophically failing. That can’t be said for other Dodge engines such as the 2.7L used in Intrepids and similar. I am not a huge MOPAR person overall.

I got home and looked it up. There is some defect where the chains on the 3.9L slap against the inside of the timing cover and clack at idle/no load. They solved in the later '90’s and you can refit the older trucks with a timing set from the newer models if you like but most people just drive them.

Anyway, I am all for the chains myself as they seem to last the life of the vehicle. I was curious if the lower rotating mass of a belt might have increased response or mileage.

Conor

I’ve heard people say they’re quieter, but never the manufacturers. Usually it’s someone offering an explanation for why they’re used.

Bottom line; they’re cheaper. Fortunately, I think customer dissatisfaction has led to manufacturers not using them as frequently. It seems that everything new has chains.

Cwatkin, your comment about the greater mass is insightful. It’s true that lower mass needs less fuel to get moving, and since engines accelerate often in normal driving that would make sense.

Its purely cost. When they were first used, new car buyers kept their cars about 3-4 years and the belt would last 4 years, so belt replacement was not a concern to the new car buyer. The manufacturer doesn’t make any money off the second owner so they are not concerned.

A first owners started keeping their cars longer, the manufacturers began increasing the life span of the belts through better materials. As long as the initial purchaser traded the car before the belt change was due, it was not a concern for the manufacturer.

It finally became a concern for the manufacturers when their customers began to hold onto the car for 10 years. Belts can be made to last that long by using more composite materials and silicone rubber, but it appears that it is cheaper to use a chain rather than upgrade the belt materials.

Absolutely no advantage to the vehicle owner. The vehicle maker will get an advantage to their bottom line by saving money during the manufacturing process.

I have heard the “quieter” argument in relation to timing gears. My parents had a 1969 Pontiac LeMans V-8 that had nylon timing gears. The timing gears failed and steel replacemetn gears were installed. I couldn’t hear any difference in the engine sound. The 1939 Chevrolet my dad owned had some kind of fiber composition for the timing gears. Again, the argument was that these fiber composition timing gears were quieter. Chevrolets of this vintage with the “Stovebolt” 6 engines were known to have timing gear failure. Fortunately, these engines were not interference engines. The tappets in these old Chevrolet engines were often so noisy that any noise of the timing gears was drowned out anyway. r
Both the 2003 Toyota 4Runner V-6 we own and the 2011 Toyata Sienna V-6 we own have timing chains and I haven’t been bothered by noise from this set up.

The solution to noisy timing gears, if there actually were noisy timing gears, would be simple anyway…helical cuts are far quieter than spur cuts. That’s why guy who come to the track with quickchange rearends used to use spur cut gears on the track for greater strength and change to helical cut gears for the ride home. Granted, they changed the ratios too.

I recently got a 1994 Geo Metro 1.0L 3cyl for gas mileage and it has a timing belt. The job on this takes like 1-2 hours to do by myself. That is a $35 kit with Gates belt, new timing seals, a tensioner/idler, etc. I went ahead and replaced the water pump which was also $35 at the same time.

Now these little cars are essentially the modern day VW bug if you can consider something 20-30 years old “modern” and are super easy to work on. Everyone says, “I bet that is a pain to work on with lots of small/tight spaces.” It is actually like working on an old pickup under the hood as it is easy to do just about anything. I can change an entire engine by myself in like 4 hours without a hoist. All I need is a car jack and a metric socket set!

Conor

All I need is a car jack and a metric socket set!
@cwatkin–a car jack and a metric socket set is a big investment in tools! The old VW bug could be repaired with kitchen utensils.
Actually, you make a good point about the Geo Metro. It would be great to have more cars to keep in repair.

Do you feel safe in a Geo?

A timing belt has its drawbacks but also some great benefits. A V engine with overhead cams, especially dual overhead cams, is much cheaper to manufacture but it is also much cheaper and simpler to repair than the chain drive model. Ford Windsor V 8s were notorious for tossing chains at 80,000 miles with manual transmission and 120,000 with automatics and even that simple, non interference engine required longer to replace the chain than a Hyundai, Mazda, Toyota or Nissan V-6 T-belt. And a Mazda 929 was an easy 2 hour job.

And let a Toyota R-22 chain slip while the head is off. That slip will cost you dearly. And BTW, check the flat rate time to replace the timing chains on a Jaguar 4.2L or Mercedes V-8.

Consumers have wised up and are rejecting cars equipped with timing belts…As a result, most manufacturers have switched back to chains, or at least use a non-interference design…

A Timing belt can make it easier to remove and replace a cylinder head. I am of the opinion that a timing belt is more durable than a timing chain if an engine is repeatedly run up to maximum RPM. For a DIY person, changing a belt several times during the life of an engine appears to be easier and cheaper than eventually changing a timing chain and its associated parts

Originally timing belts were used because they were more durable and easier to service than chains. As engines with overhead cams became more popular, a rubber belt on the outside of the block and head was much more durable and easier to service than a chain of that length which requires guides, hydraulic tensioners, and must be bathed in oil. As noted above, they also reduce engine repair costs. A Jeep Liberty has 3 timing chains, Ford V-8s have at least 2, even some 4 cylinder engines have 2 chains. Adds a lot to the cost whenever an engine has to come apart.

Timing belts may add a little to the cost of ownership of a car, but in the long run I think the cost is minimal. At least it’s predictable. I recently had the pleasure of replacing all 4 timing chains in a Lincoln LS with a V8 engine. That was a $2400 job that’s not outlined anywhere in the scheduled maintenance. As engines routinely reach 200,000 miles I’ve noticed an increase in timing chain repairs. And they cost a lot more than belts.

Don’t be fooled into thinking chain engines are better. Lots of chain engines are an interference design and lots of belt engines aren’t.

What a coincidence, ASE. Here’s the Ford timing chain replacement video