a broken chain causes many damaged valves

[shogun]

My friend Ralph (Herbie01) in Germany recently updated his homepage about his E32 740.
A lot of pics. Among others a fridge in the rear between the seats, special thick anti theft window glass, instead of the econometer he installed an oil temperature indicator for engine oil and many other things.
Have a special look under "Kettenriss" = broken chain, where you can see many pics of bended valves and the engine apart. Chain broke at 184 k km
http://people.freenet.de/Herbie01/

[mamilapon]

How common is that ****?

[632 Regal]

very common if you dont follow maintenance replacement.
How common is that ****?

[myles]

I don't recall ever seeing a replacement schedule for the timing chain. What's recommended?

[Rob]

That's what happened to my car. Cam belt snapped while driving. This was when my Dad owned the car. He had the engine re done though. Cost him R15,000 to do.

[GoldenOne]

yeah, that happened to my friends e34 m50 about a week ago, decapitated the engine and found some cool looking valves

http://free.300zxclub.com/files/2/BentValves/BMW%20011.jpg
http://free.300zxclub.com/files/2/BentValves/HP%20025.jpg
http://free.300zxclub.com/files/2/BentValves/HP%20026.jpg

all twelve exhaust valves were toast but the intakes are fine...

[mamilapon]

OK guys, lets get it right. There is a replacement schedule for a timing BELT but no replacement schedule (that i know of) for the timing CHAIN.

[mamilapon]

Regal, as far as i know you dont have to replace the CHAINS on yours, correct?

[genphreak]

OK guys, lets get it right. There is a replacement schedule for a timing BELT but no replacement schedule (that i know of) for the timing CHAIN.One does the chain when one does a short or long engine rebuild - ie head replacement or piston and ring job.

It lasts past the head rebuild point (can be as late as 500k km), but you risk damage if you don't change it then. The drive cogs tend to wear, and one changes the chain with the cogs as they do wear together. :) Nick

[yaofeng]

OK guys, lets get it right. There is a replacement schedule for a timing BELT but no replacement schedule (that i know of) for the timing CHAIN.

The timing chain is NOT a maintanance item. It lasts the life of the engine. Do you think this ever needs to be replaced? Heck, no.http://i21.photobucket.com/albums/b274/yaofengchen/BMW_95_540/Re-exposureofDSC_2598.jpg

[myles]

That's OK for you with your M60, but my M30 only has a single row chain which does wear more quickly than the double row chains.

My chain has streched such that the cam timing is bit over one third of a tooth out of allignment with the crank. I am only waiting on 1 more part before I go back in and replace the timing chain, oil pump chain, both tensioners and the cam and crank sprockets.

[Rustam]

That's OK for you with your M60, but my M30 only has a single row chain which does wear more quickly than the double row chains.

My chain has streched such that the cam timing is bit over one third of a tooth out of allignment with the crank. I am only waiting on 1 more part before I go back in and replace the timing chain, oil pump chain, both tensioners and the cam and crank sprockets.

How can one check to see if the timing chain has stretched?

[genphreak]

How can one check to see if the timing chain has stretched?That is why it has a tensioner- to take up the stretch as it occurs, as well as the slack. What happens is your cogs wear out. One look will tell you if they are worn, you need somehting like a 3mm flat section accross the peaks of each tooth on the cam gear. If in service that has been worn away and the teeth become 'sharp',any further wear actually reduces the height of the tooth and when under load the chain risks jump a tooth. Unless the chain is faulty and breaks due to a manufacturing fault (and I guess that in reality an old+worn chain is a lower risk of this that a new one), it will do this a long time before failing from wear.

Chains generally last longer than the motor as others have said.

Moral of the story is, if your M30 jumps a cog (it will become a slug/run poorly as a result) then you could well have gone past the point time at which your motor was due for a 'short motor rebuild*', or if done already the PO may have paid the wrong person to do it...

*short motor rebuild means all moving parts in the head, timing case, as many seals as you can justify/get to and the oil pump/canister.

Chains are dirt cheap. If doing major work on other worn parts, one should replace them and their gears, as well as the oil pump chain and wear parts.

In an M30, oil pump wear (and the filter canister valve) is of much greater concern than timing chaing reliability. If that fails you are also in the poo.

:) Nick

[mamilapon]

Good quality oil on a regular basis..I say!! No clogging or gumming up and therefore no starvation of oil to any part of the running gear.

[Rustam]

That is why it has a tensioner- to take up the stretch as it occurs, as well as the slack. What happens is your cogs wear out. One look will tell you if they are worn, you need somehting like a 3mm flat section accross the peaks of each tooth on the cam gear. If in service that has been worn away and the teeth become 'sharp',any further wear actually reduces the height of the tooth and when under load the chain risks jump a tooth. Unless the chain is faulty and breaks due to a manufacturing fault (and I guess that in reality an old+worn chain is a lower risk of this that a new one), it will do this a long time before failing from wear.

Chains generally last longer than the motor as others have said.

Moral of the story is, if your M30 jumps a cog (it will become a slug/run poorly as a result) then you could well have gone past the point time at which your motor was due for a 'short motor rebuild*', or if done already the PO may have paid the wrong person to do it...

*short motor rebuild means all moving parts in the head, timing case, as many seals as you can justify/get to and the oil pump/canister.

Chains are dirt cheap. If doing major work on other worn parts, one should replace them and their gears, as well as the oil pump chain and wear parts.

In an M30, oil pump wear (and the filter canister valve) is of much greater concern than timing chaing reliability. If that fails you are also in the poo.

:) Nick

When I rebuilt the head last year, I recall having aligned the crankshaft at 1st cylinder TDC I saw perfect alignment of the cam gear as described in Bentley manual. I guess that chain and sprocket are good.

I saw deformations on the pistons along the shapes of the valves, I guess, previously, the chain did in fact break resulting in the deformation.

Do you know slack distance for the oil pump chain?

[pyro]

those berrings were very well warn. the mains looked oke but the rod berrings were pritty bad