"lifetime" chain instead of timing belt


#1

Do all new cars now have chains instead of a rubber timing belt? Do they really last forever? But if they do break, they do not destroy an engine like a timing belt?


#2

All I can say is there is no such thing as life time anything on a car. Every thing will either break or wear out at some point. As for engine damage that depends on the engine. And I also depends on he definition of life time. I had a chain let go at 105k on a 69 Cutlass and one that lasted on a 63 GMC until we rid ourselves of the truck at about 200k.


#3

More and more mfrs are moving to timing chains, but there are some vehicles left with timing belts. Even though it is time-consuming, the only way to know for sure about whether or not a vehicle has a timing belt is to look at the maintenance schedule.

The cars in a new car showroom usually have the Owner’s Manual and Maintenance Schedule sitting in the glove compartment, so I would suggest that you visit the showrooms for the cars that you are really interested in, and then peruse the maintenance schedule. If a vehicle has a timing belt, the maintenance schedule for 90k, or 100k, or 105k will note the need to change the timing belt–which some mfrs refer to as a “cam belt”. If the maintenance schedule is not sitting in the glove compartment, then there is nothing wrong with asking a salesperson to get one to show to you.

However, don’t even bother asking a new car salesman your question in a direct manner, simply because most of them are so clueless or…less than honest…that either they won’t know the answer to your question, or will provide incorrect information–out of either ignorance or the intent to deceive you.

The advantage of a timing chain, aside from the fact that most of them are good for at least 200k miles, is that they do give you a warning of their impending demise. When a timing chain has stretched, it reverberates inside the inside of the metal chain cover, and it makes a noise that sounds like…a chain rattling against metal. If and when you hear this from an engine with a timing chain, it is time to start shopping around for a shop to replace it.

By contrast, timing belts give you no warning at all before they give up the ghost.


#4
Do they really last forever?

NO…But they do last a lot longer then timing belt.

But if they do break, they do not destroy an engine like a timing belt?

Having a belt or chain has NOTHING to do with if it will destroy the engine if it breaks or slips. It has to do with - if the engine is an interference engine. My first vehicle with a timing belt was my 72 Vega. When the belt snapped…I just pulled over…put a new belt on and was on my way. My Dad owned a 71 Toyota Corona…when the chain slipped - it destroyed the engine (interference engine).

Chains don’t usually break…they slip. If a chain slips a couple of teeth in an interference engine - it’s the same as if a belt breaks - destroys valves or the engine.

While chains last a lot longer then belts - if you drive long enough the chain will need to be replaced. Usually over 250k miles. I have over 260k miles on my 4runner and so far there’s no sign of chain rattle. The cost of a chain replacement (before it breaks) is 4-5 times the cost of a belt. So in the LONG run a belt might be cheaper. Much cheaper if you can do the belt yourself. Many backyard mechanics can replace a belt…but don’t possess the skills to replace a chain. While the principle of both is the same…the chain is a lot more complicated because of the introduction of lubricant. Now you have to deal with Gaskets (usually oil pans)…etc. Belts are a dry system.


#5

Timing chains seldom break causing engine destruction…Their usual failure mode is they get loose enough so they “jump timing” , they slip a tooth or two on their sprockets, which are worn too. This event usually occurs while the engine is being cranked, at engine start and it seldom causes any engine damage…If the engine starts at all, it runs very poorly…

With today’s designs, by the time the chain is approaching failure, the entire car is approaching failure…

The real weakness of the timing belt is the cost of replacing them, not something consumers look forward too, and the fact that failure can total an otherwise still serviceable car…


#6
Their usual failure mode is they get loose enough so they "jump timing" , they slip a tooth or two on their sprockets, which are worn too.

I take it your vehicles with chains are NOT interference engines. If you have an interference engine and it jumps a tooth or two it WILL destroy your engine.

The real weakness of the timing belt is the cost of replacing them, not something consumers look forward too, and the fact that failure can total an otherwise still serviceable car

You don’t keep your vehicles long enough to know how much a timing chain costs. So yes for MOST people like you the cost of timing belts is expensive. Of the past 2 SUV’s I’ve owned - at some point I would have had to replace the timing chain because they both had OVER 400k miles and the vehicle was still running good.

I plan on keeping my 4runner at least another 100k miles. It has 260k miles and it runs EXCELLENT. I wouldn’t hesitate to get in and drive to California and back. And I’m sure I’d make the trip without a hitch. So in 100k miles I’ll be approaching 400k miles. Not sure if I’ll to the chain or have it done. Not looking forward to that replacement either way. The belts on my Pathfinders…I could do in one evening when I got home from work and have it completed before I went to bed.


#7

@PvtPublic: “All I can say is there is no such thing as life time anything on a car… I had a chain let go at 105k on a 69 Cutlass and one that lasted on a 63 GMC until we rid ourselves of the truck at about 200k.”

On the '63 GMC, the timing chain did apparently last the life of the vehicle, at least the life of the vehicle while you owned it. Heck, 200,000 miles is a lot of miles for a 1963 vehicle, so it very well may have been the useful lifetime of that truck.

@MyName, so you can better understand the issue, here is an explanation of what an interference engine is:

This video even taught me something new. I had never heard about valve-to-valve interference in dual overhead cam (DOHC) engines. It looks like if you’re worried about your timing belt breaking, or your timing chain slipping, the best engine to have would be a non-interference engine with a single overhead cam (SOHC) design.

Of course I would never use a single design feature as a criteria for selecting or ruling out a vehicle. There are advantages of DOHC design that outweigh the risks, especially if the engine has a timing chain. Timing chain malfunctions are rarer than timing belt malfunctions, especially if you keep up with oil changes. In engines with timing chains, the motor oil lubricates the timing chain.

This brings up an interesting question: Have any of you ever seen a an engine with both a timing chain and a separate oil supply for the chain? It seems like that would be a good design feature since gear oil lasts much longer than motor oil.


#8

Here in the rust belt I have never replaced a timing chain, ever. Unless you are a traveling salesman it is almost impossible to wear out a timing chain before the car rusts out. If you are determined to wear out your timing chain you would have to neglect changing your oil.


#9

Cam position sensor on a modern vehicle will indicate via “Check Engine Light” if the timing slips or if the chain/sprockets wear too much to give you time to get to a repair shop before a catastrophic failure. It’s my view that a timing belt can tolerate repeated high engine revs to redline better than a chain. If you drive moderately, you should get enough life from a chain so that the rest of the vehicle will be scrap before the chain breaks or wears too much.

Having overly punished a couple of motorcycles with cam chains to where they became noisy makes me better appreciate my small Harley with timing gears.


#10

Nothing lasts forever but a timing chain should have a life expectancy much greater then a belt but still won’t be indefinite. People who keep motors young for several hundred thousand miles nay eventually have a need to replace them.


#11

Lifetime means the life of the chain. I’ve had to replace chains at 150 and 250K.


#12

I’m glad that some of you guys are being reasonable and acknowledging that timing belts aren’t some evil profit generator device, created by all the auto manufacturers, in a plot to rob the customer of his money

That was a far fetched story, but there are probably people out there who truly believe these conspiracy theories


#13

I don’t believe timing belts were installed as part of any conspiracy. I do believe that they were installed by automotive engineers who were probably near the bottom of their class. Installing them on an “interference engine” had to be done by automotive engineers who were at the bottom of their class. Timing belts are “profit generators” of sorts whether done intentionally or unintentionally.


#14

Timing chain or timing belt…doesn’t matter to me. I don’t know why anyone would base their car buying decision on chain or belt.

I have preferences, but it’s not a deal breaker.

My preference would be a non-interference/chain engine. Every vehicle we’ve bought since 1980 have been interference. All 3 vehicles we own right now have chains…and all are interference engines. I’ll tackle the chain on my 4runner when/if it needs to be replaced. I WON’T on my highlander or wifes Lexus. Both are transverse mounted and very little room in front of engine to work.


#15

As I understand it, non-interference requires deeper valve scallops in the piston’s crown. This creates flow and surface area challenges affecting emissions, mpg, etc.


#16

I don’t think that is the case. Whether an engine is an interference engine or a non-interference is a function of how far the valves open and how high the pistons are at TDC. The piston designs are typically the same in both configurations.

Interference engines were created to increase efficiency by allowing the valves to open wider.

I think it is important to specify whether you’re talking about valve-piston interference or valve-valve interference. If you don’t know what valve-valve interference is, I suggest you check out the video I posted.


#17

What about timing gears? they would still wear out of course and as far as oil goes ,viscosity has little to do with lubricity IMO-Kevin


#18

“Interference engines were created to increase efficiency by allowing the valves to open wider.”

Why not allow the valves to open wider via deeper valve relief scallops and keep it non-interference?


#19

I think you may have already answered that question. Besides, once you create a deeper valve relief scallop, you create more volume in the cylinder, reducing the engineering benefits of making it an interference engine in the first place.

In interference design benefits from more fuel and exhaust gas passing through the valves, but it also benefits from the cylinders pushing more exhaust gas out during its upstroke, reducing the amount of leftover exhaust gas in the cylinder when it pulls more fuel in.

Non-interference engines are inherently less efficient than interference engines, whether we’re talking about valve-piston interference or valve-valve interference. Many forum members here consider it a poor trade-off (efficiency for the disadvantages of interference engine design), but I’m not one of them.


#20

Interference engines have been around for at least 50 years, they are nothing new. The design has more to it than just valve reliefs in the piston or how far the valve opens. Compression ratio, valve lift duration, valve size, combustion chamber design are just a few.

Valve reliefs are generally not a good idea for efficient combustion. You want the combustion chamber to be as smooth as possible.