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Posted: 7/19/2010 10:13:09 AM EST
I sold my 2002 BMW E46 M3 about 2 weeks ago. The new owner decided he wanted to do some updates/repairs on the car before he started driving it. He read on a BMW forum that some earlier E46 M3s had a problem with the cam bolts breaking and causing the engine to blow. So he decided to check the bolts. He found 5 out of 6 bolts had broken, and the 6th bolt was worn about 50% through (check out the videos made by the new owner). He was literally a few miles away from a $10,000 repair bill. As far as it goes for me, talk about selling a car at the perfect time.

Video 1

Video 2

Video 3
Link Posted: 7/19/2010 10:14:18 AM EST
[#1]
Wow, talk about the nick of time...

I've found problems like that before, but in my case it's always AFTER the last one goes .
Link Posted: 7/19/2010 10:18:41 AM EST
[#2]





Geezus!!




WTF!!???




That's some major fucking work.




How much did you sell it for?
Link Posted: 7/19/2010 10:20:04 AM EST
[#3]
Wow, how many model cars/motors is that cam used in?
Link Posted: 7/19/2010 10:21:53 AM EST
[#4]
The Germans always make good stuff.
Link Posted: 7/19/2010 10:25:56 AM EST
[#5]
Was it just the M3s? I seem to recall hearing something about Vanos failure shortly after purchasing my 01 325 CiC and praying I didn't have any trouble with it. I sold it a year ago with over 100k on it.
Link Posted: 7/19/2010 10:26:52 AM EST
[#6]
Quoted:
Wow, how many model cars/motors is that cam used in?


No idea how many different model engines that exact cam is used in. But the S54 engine in the E46 M3 was only used in the 2001-2006 E46 M3 and the 2001-2002 MZ3 and maybe a few years in the  MZ4.

Link Posted: 7/19/2010 10:27:29 AM EST
[#7]
Quoted:

Geezus!!

WTF!!???

That's some major fucking work.

How much did you sell it for?




$16,500

Link Posted: 7/19/2010 10:28:10 AM EST
[#8]
holy shit... did BMW ever figure that problem out?
Link Posted: 7/19/2010 10:32:15 AM EST
[#9]
I have a buddy with a new M5.  He was having trans issues (it's the paddle shifter one.  Not sure what it's called.  I drive a Truck )

Anyways, it needed a 10 hour computer reprogram or some shit.  The guy at the Bimmer dealer told him if he hadn't brought it in the trans would have been toast very shortly.  $18,000 for a new one.  I'm sorry but that's just fucking stupid.
Link Posted: 7/19/2010 10:35:22 AM EST
[#10]
Definitely a problem.  Looks like failure from the VANOS using the bolts as a stop for timing adjustment.  When he pulled the one surviving bolt, the VANOS retarded the timing, he needs to turn the cam  itself to line the bolts with the bolt holes.  Then careful extraction, might be easiest with sprocket removal.  Get the service manual.




Link Posted: 7/19/2010 10:35:26 AM EST
[#11]
Quoted:
holy shit... did BMW ever figure that problem out?



BMW hasn't admitted there is a problem with the cam gear bolts, but it's obvious there is a problem with the earlier cars, because numerous people with earlier E46 M3s have checked and found broken bolts, or had their engine blow. Evidently BMW redesigned the VANOS gear bolts after a few years (the new replacement bolts are much different than the bolts in older cars) and the BMW bean counters decided it was cheaper to just fix earlier engines as they blew up rather than doing a recall, or hoped the bolts failed after the warranty expired.  Some posters are saying BMW made them pay $9500 for a new engine after their engine blew due to this issue. I'm betting there will be a class action lawsuit.

Link Posted: 7/19/2010 10:37:24 AM EST
[#12]
over rev much?


Link Posted: 7/19/2010 10:39:20 AM EST
[#13]
and why would you pay for a whole engine when you can just replace the top end?

might as well port and polish the heads and drop some more aggressive cams in too
Link Posted: 7/19/2010 10:40:54 AM EST
[#14]
Quoted:
Quoted:
holy shit... did BMW ever figure that problem out?



BMW hasn't admitted there is a problem with the cam gear bolts, but it's obvious there is a problem with the earlier cars, because numerous people with earlier E46 M3s have checked and found broken bolts, or had their engine blow. Evidently BMW redesigned the VANOS gear bolts after a few years (the new replacement bolts are much different that the bolts in older cars) and the BMW bean counters decided it was cheaper to just fix earlier engines as they blew up rather than doing a recall, or hoped the bolts failed after the warranty expired.  Some posters are saying BMW made them pay $9500 for a new engine after their engine blew due to this issue. I'm betting there will be a class action lawsuit.



I used to drive my '06 E46 pretty hard, but after the inspection where they told me they had to replace all the valve adjustment plates (IIRC), I've been babying her...
Link Posted: 7/19/2010 10:43:31 AM EST
[#15]



Quoted:



Quoted:

holy shit... did BMW ever figure that problem out?






BMW hasn't admitted there is a problem with the cam gear bolts, but it's obvious there is a problem with the earlier cars, because numerous people with earlier E46 M3s have checked and found broken bolts, or had their engine blow. Evidently BMW redesigned the VANOS gear bolts after a few years (the new replacement bolts are much different that the bolts in older cars) and the BMW bean counters decided it was cheaper to just fix earlier engines as they blew up rather than doing a recall, or hoped the bolts failed after the warranty expired.  Some posters are saying BMW made them pay $9500 for a new engine after their engine blew due to this issue. I'm betting there will be a class action lawsuit.





Using those bolts as a hard stop for the VANOS is a design error.  



 
Link Posted: 7/19/2010 10:45:11 AM EST
[#16]



Quoted:


and why would you pay for a whole engine when you can just replace the top end?



might as well port and polish the heads and drop some more aggressive cams in too


Eat the valves and they drop into the combustion chamber.  This causes rod and bearing damage.  New pistons, heads, rods and bearings?  If the exhaust valves are sodium filled (for cooling), that is a major mess.  Parts alone would be over $6k.



 
Link Posted: 7/19/2010 10:45:14 AM EST
[#17]
Quoted:
over rev much?





Never. In its stock form, you can't over-rev a E46 M3 with SMG. It has a rev limiter and the computer won't allow a downshift that over-revs the engine. That car was babied for 8 years/83K miles. I was the original owner and never tracked the car and had every single scheduled maintenance performed at the BMW dealer. It was a daily driver for me. That car was never abused. I never even let my wife drive it, not once.

Link Posted: 7/19/2010 10:47:57 AM EST
[#18]
Quoted:
and why would you pay for a whole engine when you can just replace the top end?

might as well port and polish the heads and drop some more aggressive cams in too


Maybe Vanos failure causes other severe engine damage damage like when the timing belt fails on some engines and it causes valve damage.
Link Posted: 7/19/2010 10:48:24 AM EST
[#19]
Quoted:
and why would you pay for a whole engine when you can just replace the top end?

might as well port and polish the heads and drop some more aggressive cams in too



Because when all 6 bolts fail, the sprocket slips off the end of the cam and the valves stay where they are, and the pistons come up and hit the valves. Not to mention the damage done by the intake and exhaust sprockets locking each other up. It destroys the engine. If you were idling at a red light when it happened, then you may get lucky and have minimal damage. But if it happens while at high RPM, fuggedaboutit.


More aggressive cams??? What do you think this is, a pushrod V8?? The E46 M3 engine already develops more than 100 HP per liter. When I bought the car in 2002, only two normally aspirated production cars developed more than 100 hp per liter. The other car was the Honda S2000.

Link Posted: 7/19/2010 10:52:17 AM EST
[#20]



Quoted:



Quoted:

and why would you pay for a whole engine when you can just replace the top end?



might as well port and polish the heads and drop some more aggressive cams in too




Maybe Vanos failure causes other severe engine damage damage like when the timing belt fails on some engines and it causes valve damage.


Timing chain.



 
Link Posted: 7/19/2010 10:54:56 AM EST
[#21]
Quoted:
Quoted:
Quoted:
holy shit... did BMW ever figure that problem out?



BMW hasn't admitted there is a problem with the cam gear bolts, but it's obvious there is a problem with the earlier cars, because numerous people with earlier E46 M3s have checked and found broken bolts, or had their engine blow. Evidently BMW redesigned the VANOS gear bolts after a few years (the new replacement bolts are much different that the bolts in older cars) and the BMW bean counters decided it was cheaper to just fix earlier engines as they blew up rather than doing a recall, or hoped the bolts failed after the warranty expired.  Some posters are saying BMW made them pay $9500 for a new engine after their engine blew due to this issue. I'm betting there will be a class action lawsuit.



I used to drive my '06 E46 pretty hard, but after the inspection where they told me they had to replace all the valve adjustment plates (IIRC), I've been babying her...



I think you are talking about "valve adjustment shims". Replacing those shims is normal during a valve adjustment. Different thickness shims is how they adjust the valves. A valve adjustment is required at each Inspection I which occurs about every 28,000 miles.

Link Posted: 7/19/2010 10:58:25 AM EST
[#22]
To align the cam with the sprocket, he needs to hold the sprocket and turn the cam.  Meaning valve covers have to be removed.
Link Posted: 7/19/2010 11:00:53 AM EST
[#23]
Quoted:

Quoted:
Quoted:
and why would you pay for a whole engine when you can just replace the top end?

might as well port and polish the heads and drop some more aggressive cams in too


Maybe Vanos failure causes other severe engine damage damage like when the timing belt fails on some engines and it causes valve damage.

Timing chain.
 


Some makers use a belt instead of a chain.
Link Posted: 7/19/2010 11:01:29 AM EST
[#24]



Quoted:



Quoted:




Quoted:


Quoted:

and why would you pay for a whole engine when you can just replace the top end?



might as well port and polish the heads and drop some more aggressive cams in too




Maybe Vanos failure causes other severe engine damage damage like when the timing belt fails on some engines and it causes valve damage.


Timing chain.

 




Some makers use a belt instead of a chain.


BMW uses chain.



 
Link Posted: 7/19/2010 11:04:00 AM EST
[#25]
Quoted:
To align the cam with the sprocket, he needs to hold the sprocket and turn the cam.  Meaning valve covers have to be removed.



That may be true, but the real issue is he needs special BMW equipment and tools to get everything timed properly.
Link Posted: 7/19/2010 11:04:58 AM EST
[#26]
Quoted:
Quoted:

Quoted:
Quoted:
and why would you pay for a whole engine when you can just replace the top end?

might as well port and polish the heads and drop some more aggressive cams in too


Maybe Vanos failure causes other severe engine damage damage like when the timing belt fails on some engines and it causes valve damage.

Timing chain.
 


Some makers use a belt instead of a chain.


I understood that's what you meant, and I think most people did as well. Just not Keith.
Link Posted: 7/19/2010 11:07:21 AM EST
[#27]
u got lucky so did he. How much is the repair for that?
Link Posted: 7/19/2010 11:11:08 AM EST
[#28]
can you hear any audible valve tapping when these bolts fail?    

i always loved the M3 but the crazy repair costs is what steered me away.  once you are out of warranty BEND OVER........

now that new 1m looks fun but im quite happy with my current toy


Link Posted: 7/19/2010 11:19:28 AM EST
[#29]
Quoted:
u got lucky so did he. How much is the repair for that?


To swap out $24 worth of bolts it is probably around $1000 at the dealer. If you do it yourself, it's an all day job to change the bolts. If the engine blows, the dealer charges about $9500 to install a remanufactured engine.

Link Posted: 7/19/2010 11:22:51 AM EST
[#30]



Quoted:



Quoted:


Quoted:




Quoted:


Quoted:

and why would you pay for a whole engine when you can just replace the top end?



might as well port and polish the heads and drop some more aggressive cams in too




Maybe Vanos failure causes other severe engine damage damage like when the timing belt fails on some engines and it causes valve damage.


Timing chain.

 




Some makers use a belt instead of a chain.




I understood that's what you meant, and I think most people did as well. Just not Keith.


Interference engines are due to head/valve/piston design, not the drive of the cam .  There is no question in the BMW that it is interference design, one of the many reasons BMW uses a chain.  The other issue is VANOS is hydraulic driven, timing belts don't like oil.  Meaning a critical oil seal would be needed on both sides.
 
Link Posted: 7/19/2010 11:23:51 AM EST
[#31]
Quoted:
can you hear any audible valve tapping when these bolts fail?    

i always loved the M3 but the crazy repair costs is what steered me away.  once you are out of warranty BEND OVER........

now that new 1m looks fun but im quite happy with my current toy




People are reporting the symptom is loud ticking for the first few minutes and then the ticking goes away after the engine warms up.
Link Posted: 7/19/2010 11:27:08 AM EST
[#32]
Quoted:

Quoted:
Quoted:
Quoted:

Quoted:
Quoted:
and why would you pay for a whole engine when you can just replace the top end?

might as well port and polish the heads and drop some more aggressive cams in too


Maybe Vanos failure causes other severe engine damage damage like when the timing belt fails on some engines and it causes valve damage.

Timing chain.
 


Some makers use a belt instead of a chain.


I understood that's what you meant, and I think most people did as well. Just not Keith.

Interference engines are due to head/valve/piston design, not the drive of the cam .  There is no question in the BMW that it is interference design, one of the many reasons BMW uses a chain.  The other issue is VANOS is hydraulic driven, timing belts don't like oil.  Meaning a critical oil seal would be needed on both sides.


 



Go back and read this statement 10 times, maybe you'll get what DamascusKnifemake meant. It's obvious to me what he meant. But stick to your altered reality and eventually if you say it enough times it will become true.


Maybe Vanos failure causes other severe engine damage damage like when the timing belt fails on some engines and it causes valve damage.


Link Posted: 7/19/2010 11:30:51 AM EST
[#33]




Quoted:



Quoted:

over rev much?











Never. In its stock form, you can't over-rev a E46 M3 with SMG. It has a rev limiter and the computer won't allow a downshift that over-revs the engine. That car was babied for 8 years/83K miles. I was the original owner and never tracked the car and had every single scheduled maintenance performed at the BMW dealer. It was a daily driver for me. That car was never abused. I never even let my wife drive it, not once.







This here is a smart man!  
Link Posted: 7/19/2010 11:32:07 AM EST
[#34]
Anybody with any kind of engineering sense knows that you don't use bolts for anything but compression.   In this application,

they were being used against shear forces and that isn't going to work...for long.    There should be matching bosses in the gear

and mating surface that stop rotation.  





German engineering...no wonder they lost WWII.   Too much work goes into the wrong idea.





CJ


Link Posted: 7/19/2010 11:34:38 AM EST
[#35]
Quoted:
Quoted:
holy shit... did BMW ever figure that problem out?



BMW hasn't admitted there is a problem with the cam gear bolts, but it's obvious there is a problem with the earlier cars, because numerous people with earlier E46 M3s have checked and found broken bolts, or had their engine blow. Evidently BMW redesigned the VANOS gear bolts after a few years (the new replacement bolts are much different than the bolts in older cars) and the BMW bean counters decided it was cheaper to just fix earlier engines as they blew up rather than doing a recall, or hoped the bolts failed after the warranty expired.  Some posters are saying BMW made them pay $9500 for a new engine after their engine blew due to this issue. I'm betting there will be a class action lawsuit.



This is not correct.  The issue affected '02 model year M3's made between certain dates.  They fixed the issue back in the '03 model year.  They did in fact issue a recall for the engines in question.  I know because I received the letter for my '02.  Additionally they increase the engine warranty to 10 years, 100K miles (or something close to that, I've forgotten the exact numbers), on all E46 M3 engines, not just those impacted by the recall.

This work should have been completed years ago.  It's really old news in M3 circles.
Link Posted: 7/19/2010 11:35:40 AM EST
[#36]
I was hoping one day to buy one of these used M3s as a fun daily driver(Can't afford new nor would I want to take that kind of depreciation hit).  Apparently without a warranty you are going to practically pay for a brand new one in repair costs alone.  I will have to reconsider...
Link Posted: 7/19/2010 11:36:05 AM EST
[#37]
Quoted:
Anybody with any kind of engineering sense knows that you don't use bolts for anything but compression.   In this application,
they were being used against shear forces and that isn't going to work...for long.    There should be matching bosses in the gear
and mating surface that stop rotation.  


German engineering...no wonder they lost WWII.   Too much work goes into the wrong idea.


CJ


Yes, they really seem to be suffering in the automotove department.....
Link Posted: 7/19/2010 11:37:36 AM EST
[#38]
Quoted:
Quoted:
Quoted:
holy shit... did BMW ever figure that problem out?



BMW hasn't admitted there is a problem with the cam gear bolts, but it's obvious there is a problem with the earlier cars, because numerous people with earlier E46 M3s have checked and found broken bolts, or had their engine blow. Evidently BMW redesigned the VANOS gear bolts after a few years (the new replacement bolts are much different than the bolts in older cars) and the BMW bean counters decided it was cheaper to just fix earlier engines as they blew up rather than doing a recall, or hoped the bolts failed after the warranty expired.  Some posters are saying BMW made them pay $9500 for a new engine after their engine blew due to this issue. I'm betting there will be a class action lawsuit.



This is not correct.  The issue affected '02 model year M3's made between certain dates.  They fixed the issue back in the '03 model year.  They did in fact issue a recall for the engines in question.  I know because I received the letter for my '02.  Additionally they increase the engine warranty to 10 years, 100K miles (or something close to that, I've forgotten the exact numbers), on all E46 M3 engines, not just those impacted by the recall.

This work should have been completed years ago.  It's really old news in M3 circles.



You're talking about the crank bearing recall issue. That is a different issue. My car was affected by that recall and BMW changed out the crank bearings and extended my warranty.


Link Posted: 7/19/2010 11:47:00 AM EST
[#39]



Quoted:


I have a buddy with a new M5.  He was having trans issues (it's the paddle shifter one.  Not sure what it's called.  I drive a Truck )



Anyways, it needed a 10 hour computer reprogram or some shit.  The guy at the Bimmer dealer told him if he hadn't brought it in the trans would have been toast very shortly.  $18,000 for a new one.  I'm sorry but that's just fucking stupid.


I have an '08 M5 with the 7-speed paddle shifter. I have not had any transmission issues yet and I drive pretty hard, but it is something I am mindful of. These cars have been know to get the "red cog of death" warning light and I hope to never see it.



 
Link Posted: 7/19/2010 11:58:17 AM EST
[#40]





Quoted:





Quoted:


Anybody with any kind of engineering sense knows that you don't use bolts for anything but compression.   In this application,


they were being used against shear forces and that isn't going to work...for long.    There should be matching bosses in the gear


and mating surface that stop rotation.  
German engineering...no wonder they lost WWII.   Too much work goes into the wrong idea.
CJ








Yes, they really seem to be suffering in the automotove department.....






Usually they make a fine car...but really,  someone wasn't thinking very hard about this design.  It's a mistake that would be made by a high school student hoping to get into engineering some day.





Never run bolts in shear mode unless you INTEND for them to operate as shear pins.   (I can name examples of that.) That's BASIC.   Interlocking surfaces on the mating components themselves are the obvious answer.
CJ





 
Link Posted: 7/19/2010 12:01:55 PM EST
[#41]
BMW has been goodwilling E46 M3 VANOS failures if the car has been BMW-maintained.
Link Posted: 7/19/2010 12:05:15 PM EST
[#42]
Quoted:

Quoted:
Quoted:
Quoted:

Quoted:
Quoted:
and why would you pay for a whole engine when you can just replace the top end?

might as well port and polish the heads and drop some more aggressive cams in too


Maybe Vanos failure causes other severe engine damage damage like when the timing belt fails on some engines and it causes valve damage.

Timing chain.
 


Some makers use a belt instead of a chain.


I understood that's what you meant, and I think most people did as well. Just not Keith.

Interference engines are due to head/valve/piston design, not the drive of the cam .  There is no question in the BMW that it is interference design, one of the many reasons BMW uses a chain.  The other issue is VANOS is hydraulic driven, timing belts don't like oil.  Meaning a critical oil seal would be needed on both sides.


 


VW diesels use a belt and they are an interference engine. I would consider it the weak point of the engine design myself. Just to provide an example of a belt rather than a chain. The belt was chosen supposedly to keep engine noise down btu for Christs sake its a diesel. The last noise I'm concerned about is chain vs belt.
Link Posted: 7/19/2010 5:04:21 PM EST
[#43]
You sold it for $16,500 and you still haven't re-upped your membership???





Link Posted: 7/20/2010 12:50:28 AM EST
[#44]
Quoted:
You sold it for $16,500 and you still haven't re-upped your membership???







Maybe he knows a good value when he sees it.
Link Posted: 7/20/2010 1:03:13 AM EST
[#45]
But... but... I thought BMW's were perfect!!!  How can it be possible that there is a problem when I've read right here on Arfcom that the only good cars made are BMW, Mercedes, and maybe Volvo?  Was this an American (union made) BMW or something?

Also, SHIMS? Are you serious? You have to have the valves SHIMMED every 28k miles?  REALLY?

I never bought the superiority claims before, and I didn't even know about this little nugget of hilarity!  

OP: Glad to hear you dumped it in time....
Link Posted: 7/20/2010 1:20:47 AM EST
[#46]
Quoted:

Quoted:
Quoted:
Anybody with any kind of engineering sense knows that you don't use bolts for anything but compression.   In this application,
they were being used against shear forces and that isn't going to work...for long.    There should be matching bosses in the gear
and mating surface that stop rotation.  


German engineering...no wonder they lost WWII.   Too much work goes into the wrong idea.


CJ


Yes, they really seem to be suffering in the automotove department.....


Usually they make a fine car...but really,  someone wasn't thinking very hard about this design.  It's a mistake that would be made by a high school student hoping to get into engineering some day.

Never run bolts in shear mode unless you INTEND for them to operate as shear pins.   ( I can name examples of that .) That's BASIC.   Interlocking surfaces on the mating components themselves are the obvious answer .


CJ
 


How are  ring gears ( like a Dana 60-70- etc) held on ? (lot's of big shear torque right there )

Done properly ,shouldered bolts to locate the cam timing  , usually three per sprocket  , are fine under shear .

High reving Jap  motorcycles and other's auto engines have been using them in stock and racing applications for decades .

Granted its been a while since Ive been inside an engine , so maybe somethings been lost in fastener metallurgical  technology in the past 12 years.

I guessing they over torqued at the factory or had a bad batch of bolts ......both happen more often than most know.


** ETA

Shear bolts on snow-blower augers

Sure....like a hardened dowel pin(s) Obviously stronger , but leave you with a major headache to adjust the valve timing outside the factory's drilled pin's location.

Link Posted: 7/20/2010 5:50:16 AM EST
[#47]
IF done PROPERLY, yes.  It's fine.   But that means spec'ing the bolts and designing the parts to specifically handle

shear loads through the bolts, and not being skimpy about the bolt's specs.   What's the rule...when designing parts for

shear loads between bolted parts,  increase the bolt shank size by at least one standard size and only use a minimum

of grade 5 hardware.  8 is better.  As compared to a generally similar assembly with only compression or tension loading

through the bolt length, that is.



I'm sure somewhere there's an entry in an ASTM manual on derating bolt capacities under shear load conditions.





If they ARE failing on a statistically significant basis,  then it was NOT designed right.  Bad implementation.  Or maybe

a bad batch of bolts is to blame.   That falls to QC.
Link Posted: 7/20/2010 3:15:56 PM EST
[#48]
Quoted:
But... but... I thought BMW's were perfect!!!  How can it be possible that there is a problem when I've read right here on Arfcom that the only good cars made are BMW, Mercedes, and maybe Volvo?  Was this an American (union made) BMW or something?

Also, SHIMS? Are you serious? You have to have the valves SHIMMED every 28k miles?  REALLY?

I never bought the superiority claims before, and I didn't even know about this little nugget of hilarity!  

OP: Glad to hear you dumped it in time....


Who wants a valve adjustment screw that can come loose and destroy the engine? The shim method seems like a better way to me in a high performance engine.

Link Posted: 7/20/2010 3:20:14 PM EST
[#49]



Quoted:



Quoted:

But... but... I thought BMW's were perfect!!!  How can it be possible that there is a problem when I've read right here on Arfcom that the only good cars made are BMW, Mercedes, and maybe Volvo?  Was this an American (union made) BMW or something?



Also, SHIMS? Are you serious? You have to have the valves SHIMMED every 28k miles?  REALLY?



I never bought the superiority claims before, and I didn't even know about this little nugget of hilarity!  



OP: Glad to hear you dumped it in time....




Who wants a valve adjustment screw that can come loose and destroy the engine? The shim method seems like a better way to me in a high performance engine.





Shims are far lighter.  The purpose of OHC is to reduce reciprocating mass because this enables higher RPM without valve float.  Plus it is far more precise, just requiring an assortment of shims.



 
Link Posted: 7/20/2010 3:23:34 PM EST
[#50]



Quoted:



Quoted:




Quoted:


Quoted:

Anybody with any kind of engineering sense knows that you don't use bolts for anything but compression.   In this application,

they were being used against shear forces and that isn't going to work...for long.    There should be matching bosses in the gear

and mating surface that stop rotation.  





German engineering...no wonder they lost WWII.   Too much work goes into the wrong idea.





CJ





Yes, they really seem to be suffering in the automotove department.....




Usually they make a fine car...but really,  someone wasn't thinking very hard about this design.  It's a mistake that would be made by a high school student hoping to get into engineering some day.



Never run bolts in shear mode unless you INTEND for them to operate as shear pins.   ( I can name examples of that .) That's BASIC.   Interlocking surfaces on the mating components themselves are the obvious answer .





CJ

 




How are  ring gears ( like a Dana 60-70- etc) held on ? (lot's of big shear torque right there )



Done properly ,shouldered bolts to locate the cam timing  , usually three per sprocket  , are fine under shear .



High reving Jap  motorcycles and other's auto engines have been using them in stock and racing applications for decades .



Granted its been a while since Ive been inside an engine , so maybe somethings been lost in fastener metallurgical  technology in the past 12 years.



I guessing they over torqued at the factory or had a bad batch of bolts ......both happen more often than most know.





** ETA



Shear bolts on snow-blower augers



Sure....like a hardened dowel pin(s) Obviously stronger , but leave you with a major headache to adjust the valve timing outside the factory's drilled pin's location.





The bolts were designed as physical stops for the VANOS system.  The cam timing can be modified up to 6 degrees advanced or retarded by hydraulic pressure (engine oil, pumped to as much as 1700 PSI).  The shoulders of the bolts stop a plate about 2 mm thick.  That is where the wear is from.
 
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