I'm sure there is a very simple answer.

[AV8R4AA]

Hey Guys,
I have 2 of these money pits. 2003 and 2004.
4.6 Big Red, and 4.4 Silver Bullet.

I know the N62 engine better because I have had it longer.
My new ride is the 4.6 M62.

My question is why does this engine wear out timing chain guides so fast?
Granted, it's now 13 years after it was built. But I have only 61K miles.
All the people that run that engine talk about chain guides and what a pain.

I can understand dry timing belts needing replacement at 100K miles.
Seems logical.

But an oil lubricated timing chain failing under 100K miles?
I would expect the timing chain and associated parts to last the life of
the engine.

I have owned many inline 6 cylinder BMW engines and the timing chain has never
been on the radar.

This M62 seems like it should last longer.

My question is why does these guides fail or begin to fail very early in life?

[williamx5]

Good day!

Well, the short answer of the long story is the use of one long chain... If you have done any timing work on the N62, you will note the use of two chains... The M62 uses one chain and has, what BMW calls a reversing rail... This allows the chain to travel from one side to the other under the water pump... I'm not sure of the reasoning why your 62K mile 4.6 has issues, but there you have it... It could just be from age and being brittle plastic... that is generally how they go...

My first 540i had the reversing rail go on me... it was an odd situation tho. Generally the chain with wear the plastic and slide off the front edge, making contact with the cover... Mine made two perfectly aligned groves in the aluminum... I knew I needed to do the guides when the tensioner wouldn't keep the chain tight... On a side note, my 190K mile chain did not stretch more than 3mm over the entire length, compared to the new one... the plastic on the guides just dies... and there is just so much of it!

Cheers!

[X53Jay4.8is]

Originally Posted by AV8R4AA

Hey Guys,
I have 2 of these money pits. 2003 and 2004.
4.6 Big Red, and 4.4 Silver Bullet.

I know the N62 engine better because I have had it longer.
My new ride is the 4.6 M62.

My question is why does this engine wear out timing chain guides so fast?
Granted, it's now 13 years after it was built. But I have only 61K miles.
All the people that run that engine talk about chain guides and what a pain.

I can understand dry timing belts needing replacement at 100K miles.
Seems logical.

But an oil lubricated timing chain failing under 100K miles?
I would expect the timing chain and associated parts to last the life of
the engine.

I have owned many inline 6 cylinder BMW engines and the timing chain has never
been on the radar.

This M62 seems like it should last longer.

My question is why does these guides fail or begin to fail very early in life?

Here is my theory on the wear. BMWs recommendations for oil changes for intervals is way too long. If the oil had been changed at more moderate frequencies say every 5000K from day one on synthetic then I am sure the guides would last a lot longer and better service. Keep in mind there are many people who get to 200K before the guides go. The material of the guides get brittle and once they go the timing chain makes it grooves and stretches some more keep going and jumps timing.

[X53Jay4.8is]

Originally Posted by AV8R4AA

Hey Guys,
I have 2 of these money pits. 2003 and 2004.
4.6 Big Red, and 4.4 Silver Bullet.

I know the N62 engine better because I have had it longer.
My new ride is the 4.6 M62.

My question is why does this engine wear out timing chain guides so fast?
Granted, it's now 13 years after it was built. But I have only 61K miles.
All the people that run that engine talk about chain guides and what a pain.

I can understand dry timing belts needing replacement at 100K miles.
Seems logical.

But an oil lubricated timing chain failing under 100K miles?
I would expect the timing chain and associated parts to last the life of
the engine.

I have owned many inline 6 cylinder BMW engines and the timing chain has never
been on the radar.

This M62 seems like it should last longer.

My question is why does these guides fail or begin to fail very early in life?

Greg keep in mind that the in line 6 cylinder engine that you refer to were aircraft grade motors. Cant kill a M30B35 motor. You really need to cut your ties with two X5 V8s. I would loose the 2004 4.4 and just concentrate on your 4.6is. I bet you the 4.6is that you purchased went long times before oil changes rather than an every 5000K mile change. Care from the beginning makes a huge difference.

[AV8R4AA]

Now that I fixed every snag on the 4.4. I'm going to keep it.
Coolant transfer pipe, valve stem seals, cooling system ectomy,
transmission solenoids, all new gaskets and seals. It's a brand new X5 now.
It should easily go another 100K without any problems.

[jcp240z]

As been mentioned, it is not the chain but the guides which fail. They turn brittle, break which in turn causes the chain to possibly jump catastrophically.
There is an updated chain tensioner which is said to help. Theory is that it keeps the chain tighter against the guides as they wear. A looser chain slapping against a brittle plastic causes the fracturing. I have never seen an official BMW explanation, this just what I've put together over the years, but it does seem logical.

[dannyzabolotny]

Aside from the poor tensioner design and brittle plastic, these M62's run at very high temperatures which contributes to the plastic degradation. The S62 engine has a very similar chain guide design and failures are quite uncommon, mostly because it uses thicker oil and runs at a significantly lower temperature.

That being said, it's a total crapshoot. My X5 4.6is lasted until 213k miles on original guides with the original tensioner, meanwhile others have had chain guide failures shortly after hitting 100k miles.

[sunny5280]

Originally Posted by X53Jay4.8is

Greg keep in mind that the in line 6 cylinder engine that you refer to were aircraft grade motors. Cant kill a M30B35 motor. You really need to cut your ties with two X5 V8s. I would loose the 2004 4.4 and just concentrate on your 4.6is. I bet you the 4.6is that you purchased went long times before oil changes rather than an every 5000K mile change. Care from the beginning makes a huge difference.

I'm definitely of the mindset to replace oil more often than every 5 million miles

[jopecasa]

Originally Posted by AV8R4AA

My question is why does this engine wear out timing chain guides so fast?
Granted, it's now 13 years after it was built. But I have only 61K miles.

My question is why does these guides fail or begin to fail very early in life?

Maybe your newly acquired X5.....was towing constantly and at short distances.

Normal oil temp was not attained and was pushing stress to the motor....hence failure on the guides.

.......just my opinion.

[X53Jay4.8is]

Originally Posted by sunny5280

I'm definitely of the mindset to replace oil more often than every 5 million miles

So true, BMW recommended oil change intervals are just plain ridiculous for the BMW enthusiast that intends to keep their BMW running past the 200k mark.