Theories on Cause of Timing Chain Guide Breakage
11-14-2009, 10:00 AM
#41
Registered User
I e-mailed Ted. Loading this site is slow through his dial-up connection, so he asked me to post this for him. He said he'll try to sign in later.
-------------------------------------
Here are my thoughts/opinions for the dab it is worth:
This controversy has been going on for ages, but there really should be no controversy.
Toyota originally used ALL steel back and coated guiderails in the 20R and early 22R through 1982. Those were a dual roller setup.
To save weight, (insert "cost" if you prefer..*LOL**) they redesigned to a nylon type and went to the single roller type chains. Of course with less surface area, the single roller arrangement does wear a bit more rapidly, although not a lot.
Federal government Corporate Average Fuel Economy (CAFE) requirements were the primary reason for the redesign.
The nice side effect was a net power gain from the engine though less drag, significant since it is measurable at 5-6 H/P. Less total vehicle weight also, only a small amount but ounces count when dealing with government and fines for not meeting the standards.
The tensioner is highly susceptible to debris causing the arm to stick, no matter what kind or who you purchase it from. Internal tolerences must be very close or the tensioner (which is just an oil filled shock absorber) will not operate in the first place.
Note when operating a tensioner by hand, there is a little bleed hole leakage in the back. This is perfectly normal.
There is plenty of room for clean oil at the tensioner shaft and housing bore, there is no room at all for dirt or debris of any kind. The engine is vertical, so any loose chain slaps from the firing pulse, then the guiderail snaps.
An unfortunate side effect of that guide breaking is the chain contacts the timing cover. Directly behind that contact point is a coolant jacket that can then be quickly breached. Note I did say QUICKLY! There is no coolant jacket on the passenger side, therefore no logical reason for steel backed on that side, except for what is known in the business as "customer perception."
When this type of failure happens, coolant enters the crankcase and you find you do not need a timing chain, you need an engine!
Some of us in the aftermarket saw opportunity, I should claim the idea for my own but what happened was I noted several suppliers cutting down the early style guiderails and using them in the later engines to try and cure the common driver's side breakage problem due to an upset with the tensioner. I believe (don't quote me though) that LCE was the first to see it, Tim over at DOA was also making them I even made a few that way myself.
But being lazy, and disliking metal dust from chop saws, I contracted to have the driver's side guiderail mass produced. Several others out there did exactly the same thing at about the same time.... (Darn it!...
..)
The steel backed guide has just one function: In upset conditions, it lasts longer. If the chain is slapping, it can survive long enough to get you to where repairs can be made. If it is allowed to slap long enough, that steel guide will break, also. If the chain actually breaks, well... At that point you don't care about the dang steel guide any more, anyway.
In normal conditions with no upsets, the nylon type guide will last just as long. So all the steel guide does is offer some protection. If it saves you purchasing a crankshaft just once, then it is one of the world's cheapest investments.
The other concern I constantly hear is steel filings in the oil. This is an old wive's tale, it can't happen. If it could, there would be one heck of a LOT of very mad 20R owners out there......Just my thoughts and opinions here. We have never built a a 22r/re inhouse without using the driver's side steel backed guide.
*You see, back when we did produce engines inhouse, we had to offer a warranty and we don't like buying new crankshafts, either.
*Hope this helps......*EB
-------------------------------------
Here are my thoughts/opinions for the dab it is worth:
This controversy has been going on for ages, but there really should be no controversy.
Toyota originally used ALL steel back and coated guiderails in the 20R and early 22R through 1982. Those were a dual roller setup.
To save weight, (insert "cost" if you prefer..*LOL**) they redesigned to a nylon type and went to the single roller type chains. Of course with less surface area, the single roller arrangement does wear a bit more rapidly, although not a lot.
Federal government Corporate Average Fuel Economy (CAFE) requirements were the primary reason for the redesign.
The nice side effect was a net power gain from the engine though less drag, significant since it is measurable at 5-6 H/P. Less total vehicle weight also, only a small amount but ounces count when dealing with government and fines for not meeting the standards.
The tensioner is highly susceptible to debris causing the arm to stick, no matter what kind or who you purchase it from. Internal tolerences must be very close or the tensioner (which is just an oil filled shock absorber) will not operate in the first place.
Note when operating a tensioner by hand, there is a little bleed hole leakage in the back. This is perfectly normal.
There is plenty of room for clean oil at the tensioner shaft and housing bore, there is no room at all for dirt or debris of any kind. The engine is vertical, so any loose chain slaps from the firing pulse, then the guiderail snaps.
An unfortunate side effect of that guide breaking is the chain contacts the timing cover. Directly behind that contact point is a coolant jacket that can then be quickly breached. Note I did say QUICKLY! There is no coolant jacket on the passenger side, therefore no logical reason for steel backed on that side, except for what is known in the business as "customer perception."
When this type of failure happens, coolant enters the crankcase and you find you do not need a timing chain, you need an engine!
Some of us in the aftermarket saw opportunity, I should claim the idea for my own but what happened was I noted several suppliers cutting down the early style guiderails and using them in the later engines to try and cure the common driver's side breakage problem due to an upset with the tensioner. I believe (don't quote me though) that LCE was the first to see it, Tim over at DOA was also making them I even made a few that way myself.
But being lazy, and disliking metal dust from chop saws, I contracted to have the driver's side guiderail mass produced. Several others out there did exactly the same thing at about the same time.... (Darn it!...
..)The steel backed guide has just one function: In upset conditions, it lasts longer. If the chain is slapping, it can survive long enough to get you to where repairs can be made. If it is allowed to slap long enough, that steel guide will break, also. If the chain actually breaks, well... At that point you don't care about the dang steel guide any more, anyway.
In normal conditions with no upsets, the nylon type guide will last just as long. So all the steel guide does is offer some protection. If it saves you purchasing a crankshaft just once, then it is one of the world's cheapest investments.
The other concern I constantly hear is steel filings in the oil. This is an old wive's tale, it can't happen. If it could, there would be one heck of a LOT of very mad 20R owners out there......Just my thoughts and opinions here. We have never built a a 22r/re inhouse without using the driver's side steel backed guide.
*You see, back when we did produce engines inhouse, we had to offer a warranty and we don't like buying new crankshafts, either.
*Hope this helps......*EB
11-14-2009, 10:06 AM
#42
Here are my thoughts/opinions for the dab it is worth:
>
> This controversy has been going on for ages, but there really should be no
> controversy.
1. The tensioner does not operate on oil pressure. Oil pressure simply fills it, then it acts as an oil filled shock absorber. That does bleed off but slowly, replaced by oil pressure again. If the correct filter is used, we seldom see the tensioner bleed down when the engine is off. This can happen with a worn one of course. Besides, the arm is also spring loaded, intended to take up any extra slack at startup.
2. The timing chain does not "stretch", it wears. (Same net effect, though) We can see very quickly that just a thousandth or two of wear at each wear point can add quite a bit of length to the chain. So lack of adequate oil? OH boy, very rapid wear.
3. Metal filings in the oil from the steel backed guide? Nope, doesn't happen.
4.The chain wears through the coating? Perhaps after a very long time, in normal conditions the chain side plates are designed to create a groove. This helps with fore/aft chain stability, once the rollers make contact, wear almost stops entirely.
>
> Toyota originally used ALL steel back and coated guiderails in the 20R and
> early 22R through 1982. Those were a dual roller setup.
>
> To save weight, (insert "cost" if you prefer..*LOL**) they redesigned to a
> nylon type and went to the single roller type chains. Of course with less
> surface area, the single roller arrangement does wear a bit more rapidly,
> although not a lot.
>
> Federal government Corporate Average Fuel Economy (CAFE) requirements were
> the primary reason for the redesign.
>
> The nice side effect was a net power gain from the engine though less drag,
> significant since it is measurable at 5-6 H/P. Less total vehicle weight
> also, only a small amount but ounces count when dealing with government and
> fines for not meeting the standards.
>
> The tensioner is highly susceptible to debris causing the arm to stick, no
> matter what kind or who you purchase it from. Internal tolerences must be
> very close or the tensioner (which is just an oil filled shock absorber)
> will not operate in the first place.
>
> Note when operating a tensioner by hand, there is a little bleed hole
> leakage in the back. This is perfectly normal.
>
> There is plenty of room for clean oil at the tensioner shaft and housing
> bore, there is no room at all for dirt or debris of any kind. The engine is
> vertical, so any loose chain slaps from the firing pulse, then the guiderail
> snaps.
>
> An unfortunate side effect of that guide breaking is the chain contacts the
> timing cover. Directly behind that contact point is a coolant jacket that
> can then be quickly breached. Note I did say QUICKLY! There is no coolant
> jacket on the passenger side, therefore no logical reason for steel backed
> on that side, except for what is known in the business as "customer
> perception."
>
> When this type of failure happens, coolant enters the crankcase and you find
> you do not need a timing chain, you need an engine!
>
> Some of us in the aftermarket saw opportunity, I should claim the idea for
> my own but what happened was I noted several suppliers cutting down the
> early style guiderails and using them in the later engines to try and cure
> the common driver's side breakage problem due to an upset with the
> tensioner. I believe (don't quote me though) that LCE was the first to see
> it, Tim over at DOA was also making them I even made a few that way
> myself.
>
> But being lazy, and disliking metal dust from chop saws, I contracted to
> have the driver's side guiderail mass produced. Several others out there
> did exactly the same thing at about the same time.... (Darn it!.....)
>
> The steel backed guide has just one function: In upset conditions, it lasts
> longer. If the chain is slapping, it can survive long enough to get you to
> where repairs can be made. If it is allowed to slap long enough, that steel
> guide will break, also. If the chain actually breaks, well... At that point
> you don't care about the dang steel guide any more, anyway.
>
> In normal conditions with no upsets, the nylon type guide will last just as
> long. So all the steel guide does is offer some protection. If it saves
> you purchasing a crankshaft just once, then it is one of the world's
> cheapest investments.
>
> The other concern I constantly hear is steel filings in the oil. This is an
> old wive's tale, it can't happen. If it could, there would be one heck of a
> LOT of very mad 20R owners out there......Just my thoughts and opinions
> here. We have never built a a 22r/re inhouse without using the driver's
> side steel backed guide.
>
> *You see, back when we did produce engines inhouse, we had to offer a
> warranty and we don't like buying new crankshafts, either.
>
> *Hope this helps.. BTW, I did a cut and paste, sorry about all the dohickies off to the left side........*EB
>
>
>
> This controversy has been going on for ages, but there really should be no
> controversy.
1. The tensioner does not operate on oil pressure. Oil pressure simply fills it, then it acts as an oil filled shock absorber. That does bleed off but slowly, replaced by oil pressure again. If the correct filter is used, we seldom see the tensioner bleed down when the engine is off. This can happen with a worn one of course. Besides, the arm is also spring loaded, intended to take up any extra slack at startup.
2. The timing chain does not "stretch", it wears. (Same net effect, though) We can see very quickly that just a thousandth or two of wear at each wear point can add quite a bit of length to the chain. So lack of adequate oil? OH boy, very rapid wear.
3. Metal filings in the oil from the steel backed guide? Nope, doesn't happen.
4.The chain wears through the coating? Perhaps after a very long time, in normal conditions the chain side plates are designed to create a groove. This helps with fore/aft chain stability, once the rollers make contact, wear almost stops entirely.
>
> Toyota originally used ALL steel back and coated guiderails in the 20R and
> early 22R through 1982. Those were a dual roller setup.
>
> To save weight, (insert "cost" if you prefer..*LOL**) they redesigned to a
> nylon type and went to the single roller type chains. Of course with less
> surface area, the single roller arrangement does wear a bit more rapidly,
> although not a lot.
>
> Federal government Corporate Average Fuel Economy (CAFE) requirements were
> the primary reason for the redesign.
>
> The nice side effect was a net power gain from the engine though less drag,
> significant since it is measurable at 5-6 H/P. Less total vehicle weight
> also, only a small amount but ounces count when dealing with government and
> fines for not meeting the standards.
>
> The tensioner is highly susceptible to debris causing the arm to stick, no
> matter what kind or who you purchase it from. Internal tolerences must be
> very close or the tensioner (which is just an oil filled shock absorber)
> will not operate in the first place.
>
> Note when operating a tensioner by hand, there is a little bleed hole
> leakage in the back. This is perfectly normal.
>
> There is plenty of room for clean oil at the tensioner shaft and housing
> bore, there is no room at all for dirt or debris of any kind. The engine is
> vertical, so any loose chain slaps from the firing pulse, then the guiderail
> snaps.
>
> An unfortunate side effect of that guide breaking is the chain contacts the
> timing cover. Directly behind that contact point is a coolant jacket that
> can then be quickly breached. Note I did say QUICKLY! There is no coolant
> jacket on the passenger side, therefore no logical reason for steel backed
> on that side, except for what is known in the business as "customer
> perception."
>
> When this type of failure happens, coolant enters the crankcase and you find
> you do not need a timing chain, you need an engine!
>
> Some of us in the aftermarket saw opportunity, I should claim the idea for
> my own but what happened was I noted several suppliers cutting down the
> early style guiderails and using them in the later engines to try and cure
> the common driver's side breakage problem due to an upset with the
> tensioner. I believe (don't quote me though) that LCE was the first to see
> it, Tim over at DOA was also making them I even made a few that way
> myself.
>
> But being lazy, and disliking metal dust from chop saws, I contracted to
> have the driver's side guiderail mass produced. Several others out there
> did exactly the same thing at about the same time.... (Darn it!...
..)>
> The steel backed guide has just one function: In upset conditions, it lasts
> longer. If the chain is slapping, it can survive long enough to get you to
> where repairs can be made. If it is allowed to slap long enough, that steel
> guide will break, also. If the chain actually breaks, well... At that point
> you don't care about the dang steel guide any more, anyway.
>
> In normal conditions with no upsets, the nylon type guide will last just as
> long. So all the steel guide does is offer some protection. If it saves
> you purchasing a crankshaft just once, then it is one of the world's
> cheapest investments.
>
> The other concern I constantly hear is steel filings in the oil. This is an
> old wive's tale, it can't happen. If it could, there would be one heck of a
> LOT of very mad 20R owners out there......Just my thoughts and opinions
> here. We have never built a a 22r/re inhouse without using the driver's
> side steel backed guide.
>
> *You see, back when we did produce engines inhouse, we had to offer a
> warranty and we don't like buying new crankshafts, either.
>
> *Hope this helps.. BTW, I did a cut and paste, sorry about all the dohickies off to the left side........*EB
>
>
11-14-2009, 10:13 AM
#44
Registered User
How does the rubber/plastic used on metal guides hold up compared to the factory plastic guides? I haven't seen anyone mention how many miles (or years or both) they've gotten from the metal backed guide.
11-14-2009, 10:19 AM
#45
An old wise saying is that a chain is supose to last the life of the vehcile.... well thats not always the case. Especailly with these type engines. Toyota is not a cheap lowbudge company they made it the way they did for a reason. The biggest one is gas mileage. A metal guide will break just as easy, once that chain starts slappin. Theres alot of force on that chain going 1-4k rpms. Its not going to stop for a lil piece of plastic or lil piece of metal it will eat right through it and the timing cover. So toyota knew it would have to be replaced every so often. To extend the life of the engine.
11-14-2009, 10:44 AM
#46
Registered User
so basically it doesn't matter if its metal or plastic. except for the people that keep driving there yota even though there engine sounds like it has gravel in it?
11-14-2009, 10:48 AM
#47
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http://www.expeditionportal.com/foru...t=23005&page=2
Post #17
Makes me think about these new metal back guides I'm about to use.
I know I have over 1000 miles on the broke stock style ones in there. Was on a trip to KY when it went out.
Post #17
Makes me think about these new metal back guides I'm about to use.
I know I have over 1000 miles on the broke stock style ones in there. Was on a trip to KY when it went out.
11-15-2009, 05:11 AM
#50
Registered User
On the expedition portal post, that was DaveInDenver. He'd posted in a thread I'd started a while back showing those same pics. He wasn't sure why it failed and neither was anyone else. His TC assembly did fail early.
In response to Kiroshu, if what you're saying is that Dave's unfortunate circumstance was a result of lack of regular maintenance, it wasn't. It failed at 45k.
My last TC failure was just under the 90k mark. I had a quality kit with Japanese parts..........ie. the nylon guides. Not sure it would've mattered if it was metal or not. My engine was toast. The guide broke, chain snapped (I assumed from hitting the guide mounting bolts noted by the abrasion on them), and I bent six valves. It was running well enough except occasionally.....very occasionally.....the motor would race at idle and some slack chain noise. Well, I should've stop it right then and fixed it, but I always needed the vehicle, it was the middle of winter, and since it didn't have that "critical" sound against the cover I figured I had some time until it was more convenient. Wrong. I found bits and pieces everywhere behind the cover, in the crank gear (probably causing the chain to jump track), and in the oil pan. The timing cover broke down around that crescent shaped piece opposite side of the oil pump and surrounding the crank gear area. Metal had let loose and the smallest particles got into the oil system embedding some particulates in the crank bearings. No damage to the crankshaft, though. I attribute that fortune to the lead babbitt bearings Toyota used at factory and possibly my use of synthetic oil. I speculate on the oil part, though.
So, I think what Ted says is true. At that point, screw the dang guides. Plastic or metal, you gotta listen for the sounds. I do wonder how differently it would've gone with a steel guide. I have one in my motor now........been in for about a year and a half, but I'm not driving the runner any longer due to frame failure.
In response to Kiroshu, if what you're saying is that Dave's unfortunate circumstance was a result of lack of regular maintenance, it wasn't. It failed at 45k.
My last TC failure was just under the 90k mark. I had a quality kit with Japanese parts..........ie. the nylon guides. Not sure it would've mattered if it was metal or not. My engine was toast. The guide broke, chain snapped (I assumed from hitting the guide mounting bolts noted by the abrasion on them), and I bent six valves. It was running well enough except occasionally.....very occasionally.....the motor would race at idle and some slack chain noise. Well, I should've stop it right then and fixed it, but I always needed the vehicle, it was the middle of winter, and since it didn't have that "critical" sound against the cover I figured I had some time until it was more convenient. Wrong. I found bits and pieces everywhere behind the cover, in the crank gear (probably causing the chain to jump track), and in the oil pan. The timing cover broke down around that crescent shaped piece opposite side of the oil pump and surrounding the crank gear area. Metal had let loose and the smallest particles got into the oil system embedding some particulates in the crank bearings. No damage to the crankshaft, though. I attribute that fortune to the lead babbitt bearings Toyota used at factory and possibly my use of synthetic oil. I speculate on the oil part, though.
So, I think what Ted says is true. At that point, screw the dang guides. Plastic or metal, you gotta listen for the sounds. I do wonder how differently it would've gone with a steel guide. I have one in my motor now........been in for about a year and a half, but I'm not driving the runner any longer due to frame failure.
11-15-2009, 08:51 AM
#51
Contributing Member
lol, you wanna stop the "no oil pressure at startup" issue, just install a momentary kill-switch in the cab. When you go to start it, hit the switch to kill the ignition for a second or two, and turn the motor over a few times, and you'll cylce the oil through the motor and bring the pressure up, then let off the kill-switch and start the motor like normal. Problem solved! 
11-15-2009, 10:08 AM
#52
Registered User
lol, you wanna stop the "no oil pressure at startup" issue, just install a momentary kill-switch in the cab. When you go to start it, hit the switch to kill the ignition for a second or two, and turn the motor over a few times, and you'll cylce the oil through the motor and bring the pressure up, then let off the kill-switch and start the motor like normal. Problem solved!
And, if you think about it, he's obviously right. You have to hold the tensioner back with a rubberband or whatever when installing the chain. Then, release the tensioner and it tightens the chain up. It's spring loaded, eh. I thought about that this morning over my first cup of coffee. A "duh!" moment! I'd always thought it was operated on oil pressure.
11-15-2009, 10:09 AM
#53
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11-15-2009, 10:39 AM
#54
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the chain. Then, release the tensioner and it tightens the chain up. It's spring loaded, eh. I thought about that this morning over my first cup of coffee. A "duh!" moment! I'd always thought it was operated on oil pressure.
11-15-2009, 11:07 AM
#55
Registered User
No. If you read Ted's post he says "it does not operate on oil pressure. Oil pressure simply fills it". Think about it, guys.
11-15-2009, 11:10 AM
#56
Registered User
BTW, oil in a shock absorber acts a dampener to shock. It does not act to keep tension. If it's air/oil, then air does. If it's spring loaded with oil, then the spring does.
11-15-2009, 11:22 AM
#57
Registered User
Well, have you ever built or rebuilt a shock absorber? Okay.......for example: I have an old, Marzocchi air/oil shock on my mtn bike. I've rebuilt it twice since I bought it in '93. Point is, it has oil in it and seals, but without the air the thing goes completely limp....pfffth!.....no shock absorption. Take a shock with spring. No oil in it (or any way to dampen) and it kinda just springs up and down with no control. The oil dampens the spring. See?
11-15-2009, 11:51 AM
#58
Registered User
Hm....I didn't think you did from reading post #73..........which strangely enough seems to have changed.
Look........I'm not splitting hairs here, gnarly. But, if someone reads something that plainly says how something works and then goes back to say,"well, I think it works this way" which is atleast somewhat different than the way it was just explained, don't you find it interesting? Besides, Peckinpah was responding to my post and I was responding to his.........initially. If Peckinpah wants to respond to my post in a manner that appears to "debate" (too strong of a word, but for lack of a better one) what I've just said, it's perfectly okay for me to point out the contradiction. And, if what we're talking about here is a technicality that Peckinpah asked for (insert thread title), why shouldn't we kinda get clear on the subject. It's certainly to our advantage.
Look........I'm not splitting hairs here, gnarly. But, if someone reads something that plainly says how something works and then goes back to say,"well, I think it works this way" which is atleast somewhat different than the way it was just explained, don't you find it interesting? Besides, Peckinpah was responding to my post and I was responding to his.........initially. If Peckinpah wants to respond to my post in a manner that appears to "debate" (too strong of a word, but for lack of a better one) what I've just said, it's perfectly okay for me to point out the contradiction. And, if what we're talking about here is a technicality that Peckinpah asked for (insert thread title), why shouldn't we kinda get clear on the subject. It's certainly to our advantage.
11-15-2009, 02:08 PM
#60
Registered User
Regardless of guide type, what can we do to get the best life possible out of the timing system?
Ted emphasizes not overtorquing the tensioner bolts. 12 ft/lbs. max, and use a 1/4" or 3/8" torque wrench accurate in that range. The bolts being too tight can distort the body and bind the plunger.
He also says double check that the oil pump bolt doesn't protrude far enough to interfere with the chain. I presume failure from that would happen quickly.
And, at least when using a metal backed guide, adjust it (has some wiggle room) so there is clearance, or at most only light contact, between guide and chain.
Anything else?
Ted emphasizes not overtorquing the tensioner bolts. 12 ft/lbs. max, and use a 1/4" or 3/8" torque wrench accurate in that range. The bolts being too tight can distort the body and bind the plunger.
He also says double check that the oil pump bolt doesn't protrude far enough to interfere with the chain. I presume failure from that would happen quickly.
And, at least when using a metal backed guide, adjust it (has some wiggle room) so there is clearance, or at most only light contact, between guide and chain.
Anything else?
