How often to change timing chain?
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Originally Posted By: jrustles
It seems some modern long DOHC chains seem to be sensitive, particularly in CAFE regions and when oil degrades/shears beyond suitability. BMW is not immune, but they seem to be faring the best IMO. OHV timing chains are stocky and short and generally do much better.
Really? Ford's Duratec engines have exceedingly low timing chain issues on their DOHC engines, even with the their "CAFE oil".
It seems some modern long DOHC chains seem to be sensitive, particularly in CAFE regions and when oil degrades/shears beyond suitability. BMW is not immune, but they seem to be faring the best IMO. OHV timing chains are stocky and short and generally do much better.
Really? Ford's Duratec engines have exceedingly low timing chain issues on their DOHC engines, even with the their "CAFE oil".
ls1mike
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Only if I am in there for something. I did the Trans Am when I put the Cam in. Upgraded to a double roller.
Kestas
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On the old V8 blocks, the rule of thumb was to rock the crank back and forth and watch the distributor. If there was more than 10° of slop, the timing set needed to be replaced.
Then there's the old V8s that had phenolic or nylon coated gears. Those wore out quickly.
Some newer designs have tensioners that take up slop and wear... to a point.
It would help to know what model we're dealing with.
Then there's the old V8s that had phenolic or nylon coated gears. Those wore out quickly.
Some newer designs have tensioners that take up slop and wear... to a point.
It would help to know what model we're dealing with.
JHZR2
Staff member
well engineered engines will have a condemnation point. Before that, wear ("stretch") can be offset with a woodruff key that can take it back by a few degrees.
Good engines will have a way of measuring the wear on the chain.
Good engines will have a way of measuring the wear on the chain.
It's not listed as a maintenance item in my I35. I am just going to keep using good oil, make sure the level never gets low and fuggedaboutit.
I love my 4.9L Ford that uses two helical gears and no timing chain or belt. In all the years I've been driving I either owned 4.9L Ford engines that didn't have a chain or belt to worry about, everything else I owned I never had to replace a timing chain. In fact I gave it little to no thought. Some of these new engines use timing chains so long its scary. The tensioners can only take up so much slop. I'd imagine those are a different story.
Depends on the motor. Some like the old Mercedes V8's had very long chains with not the best guide design. So at 100k at least the guides needed to be done.
The old XJ8's come to mind as well, Jag's stupid little jumper chains to the outside cam's failed quite often.
OHC motors tend to have very long chains, so they wear more than say a SBC.
It also depends if its a double or single chain. Off the top of my head Jag and the new Ford engines I have seen apart use a single chain, which IMHO is a cost saving measure. A double chain is stronger.
The old XJ8's come to mind as well, Jag's stupid little jumper chains to the outside cam's failed quite often.
OHC motors tend to have very long chains, so they wear more than say a SBC.
It also depends if its a double or single chain. Off the top of my head Jag and the new Ford engines I have seen apart use a single chain, which IMHO is a cost saving measure. A double chain is stronger.
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Originally Posted By: dparm
One way to tell if the chain is truly stretched out is to use OBD2 software to monitor specific data blocks for the tensioners. There is an upper and lower limit, and if the tensioner is constantly running at those limits it tends to indicate the chain has stretched.
Unless your BMW V8 has some fancy tensoners they are just oil pressure filled, ie the oil pressure fills them up and pushes them against the chain.
The way you tell is you have to pull the valve covers off. Their will be timing marks on the crank pully as well as the cams. The procedure is in the FSM and very simple, just rotate the crank around until the marks either line up or don't. The FSM will specify how much chain "stretch" is acceptable. The only way to eliminate it is to replace the chain, sometimes they have offset keys but IMHO that's more of a band aid.
Typically, and this is a very, very rough rule, you get 1 degree of chain stretch per 100k miles on a well maintained car that uses a quality oil. Around the 200k-300k is when you want to take a look at the TC. I don't know how the chain on your M motor is set up, it might have one long one like on Mercedes V8, or they might do a couple inner chains with jumpers like Jag does. Another option is inner chains with gears to pick up the four cams.
The most expensive option which AFAIK only Rolls Royce and maybe a handful of racing cars use is gears. The problem with gears is unless they are fit to perfection they are loud. Each 6 3/4L RR V8 took 80 hours of hand fitting at the factory to make sure the timing gears meshed perfectly.
One way to tell if the chain is truly stretched out is to use OBD2 software to monitor specific data blocks for the tensioners. There is an upper and lower limit, and if the tensioner is constantly running at those limits it tends to indicate the chain has stretched.
Unless your BMW V8 has some fancy tensoners they are just oil pressure filled, ie the oil pressure fills them up and pushes them against the chain.
The way you tell is you have to pull the valve covers off. Their will be timing marks on the crank pully as well as the cams. The procedure is in the FSM and very simple, just rotate the crank around until the marks either line up or don't. The FSM will specify how much chain "stretch" is acceptable. The only way to eliminate it is to replace the chain, sometimes they have offset keys but IMHO that's more of a band aid.
Typically, and this is a very, very rough rule, you get 1 degree of chain stretch per 100k miles on a well maintained car that uses a quality oil. Around the 200k-300k is when you want to take a look at the TC. I don't know how the chain on your M motor is set up, it might have one long one like on Mercedes V8, or they might do a couple inner chains with jumpers like Jag does. Another option is inner chains with gears to pick up the four cams.
The most expensive option which AFAIK only Rolls Royce and maybe a handful of racing cars use is gears. The problem with gears is unless they are fit to perfection they are loud. Each 6 3/4L RR V8 took 80 hours of hand fitting at the factory to make sure the timing gears meshed perfectly.
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My experience has been that the chains outlast the guides and tensioners in OHC engines. I consider them to be lifetime, but frequently some ancillary piece will wear.
Being older and wiser now, I actually lean more toward belts. They are usually not too hard to replace and you do not have to break an oil seal to get to them.
I guess the question would be, is it easier to change a belt twice, or a chain once to get to 270k miles?
Or I guess a better question would be how many engines/cars actually stay in service long enough to get to 200k+, aside from the people on this forum.
This topic is close to heart right now because at 270k miles, our '97 Nissan pickup has broken its second set of improved chain guides and will now require its second cam chain replacement.
Being older and wiser now, I actually lean more toward belts. They are usually not too hard to replace and you do not have to break an oil seal to get to them.
I guess the question would be, is it easier to change a belt twice, or a chain once to get to 270k miles?
Or I guess a better question would be how many engines/cars actually stay in service long enough to get to 200k+, aside from the people on this forum.
This topic is close to heart right now because at 270k miles, our '97 Nissan pickup has broken its second set of improved chain guides and will now require its second cam chain replacement.
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No set interval, if it starts to make noise, might want to change it in another 50K miles.
Originally Posted By: blackman777
How often to change timing chain?
My manual provides no answer. How often should timing chains be replaced? 200,000 miles? 300,000?
THIS implies that it is a regular maintenance item...it is not...like struts and other suspension parts, they are replaced when they die...it's not a question of being "out of spec" like alignment, or a preventative maintenance part like a timing belt.
Perhaps a better question or three might be:
Have you replaced a timing chain BEFORE it broke...? Why?
At what mileage did it need replacement?
How often to change timing chain?
My manual provides no answer. How often should timing chains be replaced? 200,000 miles? 300,000?
THIS implies that it is a regular maintenance item...it is not...like struts and other suspension parts, they are replaced when they die...it's not a question of being "out of spec" like alignment, or a preventative maintenance part like a timing belt.
Perhaps a better question or three might be:
Have you replaced a timing chain BEFORE it broke...? Why?
At what mileage did it need replacement?
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Originally Posted By: KitaCam
Originally Posted By: blackman777
How often to change timing chain?
My manual provides no answer. How often should timing chains be replaced? 200,000 miles? 300,000?
THIS implies that it is a regular maintenance item...it is not...like struts and other suspension parts, they are replaced when they die...it's not a question of being "out of spec" like alignment, or a preventative maintenance part like a timing belt.
Perhaps a better question or three might be:
Have you replaced a timing chain BEFORE it broke...? Why?
At what mileage did it need replacement?
+1. This is engine specific - with most engine designs the chain never fails, but certain engines have issues with the timing chain system that causes them to fail prematurely. There are almost always telltale signs but you need to research specifically for your vehicle/engine so you know what to watch out for and expect.
Originally Posted By: blackman777
How often to change timing chain?
My manual provides no answer. How often should timing chains be replaced? 200,000 miles? 300,000?
THIS implies that it is a regular maintenance item...it is not...like struts and other suspension parts, they are replaced when they die...it's not a question of being "out of spec" like alignment, or a preventative maintenance part like a timing belt.
Perhaps a better question or three might be:
Have you replaced a timing chain BEFORE it broke...? Why?
At what mileage did it need replacement?
+1. This is engine specific - with most engine designs the chain never fails, but certain engines have issues with the timing chain system that causes them to fail prematurely. There are almost always telltale signs but you need to research specifically for your vehicle/engine so you know what to watch out for and expect.
Timing chains should be inspected based on engine design and known failure points.
Also yes I have replaced TC's in the past.
Typically and again I'm generalizing here, but on an OHC engine around the 200k-300k mark your going to want to inspect the chain and chain guides for wear and stretch. 99% of people never do and 99% cars die around their or soon after.
Also yes I have replaced TC's in the past.
Typically and again I'm generalizing here, but on an OHC engine around the 200k-300k mark your going to want to inspect the chain and chain guides for wear and stretch. 99% of people never do and 99% cars die around their or soon after.
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If I am doing a cam swap, like I have been taking way to long to do on my 95, I will change the chain and anything associated with timing within reason. Too much money invested to have something so cheap fail or cause a variable.
Originally Posted By: hattaresguy
dparm said:
Originally Posted By: hattaresguy
Originally Posted By: dparm
One way to tell if the chain is truly stretched out is to use OBD2 software to monitor specific data blocks for the tensioners. There is an upper and lower limit, and if the tensioner is constantly running at those limits it tends to indicate the chain has stretched.
Unless your BMW V8 has some fancy tensoners they are just oil pressure filled, ie the oil pressure fills them up and pushes them against the chain.
The way you tell is you have to pull the valve covers off. Their will be timing marks on the crank pully as well as the cams. The procedure is in the FSM and very simple, just rotate the crank around until the marks either line up or don't. The FSM will specify how much chain "stretch" is acceptable. The only way to eliminate it is to replace the chain, sometimes they have offset keys but IMHO that's more of a band aid.
Typically, and this is a very, very rough rule, you get 1 degree of chain stretch per 100k miles on a well maintained car that uses a quality oil. Around the 200k-300k is when you want to take a look at the TC. I don't know how the chain on your M motor is set up, it might have one long one like on Mercedes V8, or they might do a couple inner chains with jumpers like Jag does. Another option is inner chains with gears to pick up the four cams.
The most expensive option which AFAIK only Rolls Royce and maybe a handful of racing cars use is gears. The problem with gears is unless they are fit to perfection they are loud. Each 6 3/4L RR V8 took 80 hours of hand fitting at the factory to make sure the timing gears meshed perfectly.
There are datablocks that indicate the amount of adjustment requested by the engine computer. This was the case on my old S4 and I suspect many other companies do something similar.
Originally Posted By: dparm
One way to tell if the chain is truly stretched out is to use OBD2 software to monitor specific data blocks for the tensioners. There is an upper and lower limit, and if the tensioner is constantly running at those limits it tends to indicate the chain has stretched.
Unless your BMW V8 has some fancy tensoners they are just oil pressure filled, ie the oil pressure fills them up and pushes them against the chain.
The way you tell is you have to pull the valve covers off. Their will be timing marks on the crank pully as well as the cams. The procedure is in the FSM and very simple, just rotate the crank around until the marks either line up or don't. The FSM will specify how much chain "stretch" is acceptable. The only way to eliminate it is to replace the chain, sometimes they have offset keys but IMHO that's more of a band aid.
Typically, and this is a very, very rough rule, you get 1 degree of chain stretch per 100k miles on a well maintained car that uses a quality oil. Around the 200k-300k is when you want to take a look at the TC. I don't know how the chain on your M motor is set up, it might have one long one like on Mercedes V8, or they might do a couple inner chains with jumpers like Jag does. Another option is inner chains with gears to pick up the four cams.
The most expensive option which AFAIK only Rolls Royce and maybe a handful of racing cars use is gears. The problem with gears is unless they are fit to perfection they are loud. Each 6 3/4L RR V8 took 80 hours of hand fitting at the factory to make sure the timing gears meshed perfectly.
There are datablocks that indicate the amount of adjustment requested by the engine computer. This was the case on my old S4 and I suspect many other companies do something similar.
Originally Posted By: dparm
Chains are lifetime, generally speaking. They don't need to be changed. Even if they stretch, there are tensioners on the guides that will adjust as necessary.
IT is usually these tensioners that fail and can cause engine failure as a result.
Most have parts that rub down over time and require replacement and, therefore, are considered maintenance items.
I had to change the upper tensioner in my 1996 Sentra years back. It had rubbed down, but not enough to reach the bare metal and cause catastrophic failure. The car had over 230k miles on it.
I also experienced a timing chain tension failure in my Saturn @ 180k miles. The car survived but had to be towed.
Chains are lifetime, generally speaking. They don't need to be changed. Even if they stretch, there are tensioners on the guides that will adjust as necessary.
IT is usually these tensioners that fail and can cause engine failure as a result.
Most have parts that rub down over time and require replacement and, therefore, are considered maintenance items.
I had to change the upper tensioner in my 1996 Sentra years back. It had rubbed down, but not enough to reach the bare metal and cause catastrophic failure. The car had over 230k miles on it.
I also experienced a timing chain tension failure in my Saturn @ 180k miles. The car survived but had to be towed.
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