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  #41  
Old 05-06-2020, 02:52 PM
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On the M62, the normal progression is;

1) loss of tension at the tensioner
2) chain will loosen and slap the bottom chain guide when you drive over a bump
3) the brittle plastic will shatter and end up in the oil pan
4) this adds a significant amount of apparent length to the chain
5) tensioner can no longer keep the chain tight at all
6) chain will slap anywhere and break more of the brittle plastic
7) tensioner will bottom out and can't even hold chain taught at all
8) the spring pressure of the intake valves on bank one will "snap" the bank one secondary timing chain "advanced" and that after the obvious rattle sound is the typical confirmation of chain guide failure.
9) if left long enough, the chain will get enough slack it will hop off a sprocket, and mass destruction happens.
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  #42  
Old 05-06-2020, 03:00 PM
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The N62 has a solid chain guide design that doesn't usually shatter like M62 so I'm very curious to see what happened to allow this to happen. I'm guessing chain guide broke to give enough slack and allow the chain maybe to take a shorter path around a corner that used the solinoid as a make shift chain guide.

It's really a miracle something far worse didn't happen.

Query: why was the tensioner replaced 30k km ago? And how many km on the odometer now? My consern is that something done during that repair caused the lack of oil/tensioner pressure that usually is the start of this type of failure.
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  #43  
Old 05-06-2020, 03:48 PM
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Originally Posted by andrewwynn View Post
The N62 has a solid chain guide design that doesn't usually shatter like M62 so I'm very curious to see what happened to allow this to happen. I'm guessing chain guide broke to give enough slack and allow the chain maybe to take a shorter path around a corner that used the solinoid as a make shift chain guide.

It's really a miracle something far worse didn't happen.

Query: why was the tensioner replaced 30k km ago? And how many km on the odometer now? My consern is that something done during that repair caused the lack of oil/tensioner pressure that usually is the start of this type of failure.
Well I bought the car from a man last year who had bought the car with broken vanos and he has replaced the vanos and reset timing just to see if he was able to fix the car.

It has worked just fine until last week when I heard the strange sound and I thougt it was the waterpump on the way to fail. I don΄t know why they changed the chains, tensioner etc but something must have happened. I think the odo is about 18700 swedish miles.

There was a lot of debree from the broken solenoid and chain guide in the filter of the upper vanos solenoid.

I dont think there is lack of oil pressure in that case it should have jumped the vanos sprocket, there could be a broken link on the chain to have seen that on one car before. Well it will be interesting to see what has happened.
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  #44  
Old 05-06-2020, 08:43 PM
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A peek inside shows the chain nowhere near the solinoid but inline with it.

The only way I can see the chain hitting it is if a large piece of chain guide is missing to allow enough slack that the chain could whip from momentum into the inside somehow taking a sharp corner. Bank one or two and which side of the solinoid was chewed into?

I'm very curious. It's amazing the chain didn't bind/break. That's pretty lucky.

Check your tensioner vs OEM style when you do you recovery. Also other things like if like M62 there is that oil check valve or anything that could have blocked proper oil flow. The chain tensioner applies a shit ton of force compared to the little spring that just holds it until oil pressure builds.
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  #45  
Old 05-07-2020, 12:27 AM
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Originally Posted by andrewwynn View Post


A peek inside shows the chain nowhere near the solinoid but inline with it.

The only way I can see the chain hitting it is if a large piece of chain guide is missing to allow enough slack that the chain could whip from momentum into the inside somehow taking a sharp corner. Bank one or two and which side of the solinoid was chewed into?

I'm very curious. It's amazing the chain didn't bind/break. That's pretty lucky.

Check your tensioner vs OEM style when you do you recovery. Also other things like if like M62 there is that oil check valve or anything that could have blocked proper oil flow. The chain tensioner applies a shit ton of force compared to the little spring that just holds it until oil pressure builds.
Bank 2 and the intake side on the solenoid was chewed up. Its the lower solenoid that has been damaged.
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  #46  
Old 05-07-2020, 12:41 AM
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Originally Posted by andrewwynn View Post


A peek inside shows the chain nowhere near the solinoid but inline with it.

The only way I can see the chain hitting it is if a large piece of chain guide is missing to allow enough slack that the chain could whip from momentum into the inside somehow taking a sharp corner. Bank one or two and which side of the solinoid was chewed into?

I'm very curious. It's amazing the chain didn't bind/break. That's pretty lucky.

Check your tensioner vs OEM style when you do you recovery. Also other things like if like M62 there is that oil check valve or anything that could have blocked proper oil flow. The chain tensioner applies a shit ton of force compared to the little spring that just holds it until oil pressure builds.
Bank 2 and the intake side on the solenoid was chewed up. Its the lower solenoid that has been damaged.
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  #47  
Old 05-07-2020, 04:14 PM
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So I remembered watching a Russian video with English voice over of start to finish assembly of an N62. Everybody should watch just to be awed at the enginerding.


https://youtu.be/UTdCUJEw5lM

But I was hoping to see a better look at the timing chain arrangement;



You aren't going to find a better view with the lower timing cover on!



Here's the blow apart from real OEM or similar.

If the chain is still turning and the engine can still turn over; first that is a miracle! Definitely quit while you are ahead but here's my best guess with the new info I have.

Notice how close the chain gets to the vanos solinoid socket: mere mm away.

My bet is that the bottom chain guide (yellow arrow, part 7) disintegrated or broke free, allowing the bottom part of the chain to pull straight from the crank sprocket to the exhaust vanos. This gave the chain enough extra apparent length and the tensioner guide was pushed much farther in than design and literally chain sawed though the side of the vanos cylinder socket.

This is not great news because it means at the very least some alumaweld rebuilding of that vanos socket will be required. (though actually the pressure is low enough JB weld should work).

The N62 chains are maybe half or 60% the length of M62 and that onky had about 8mm stretch over 170,000 miles so it's really not possible stretch is part of the equation.

The beefy solid guides have practically eliminated the M62 type guide failure that is so well known in X5 circles. This is the first case I've ever seen actually.

I'll be very interested to see details of what happened to part 7. And I'm a little surprised if I'm correct that the tensioner guide had enough over-run to push the chain through part of the head, it should definitely have a stop so it's maybe more likely the weight and momentum of the chain just developed a loose loop of chain that came down to cut the vanos solinoid socket.

I think that's my updated theory: the chain was loose enough to come free from the tensioner guide and whip into the solinoid socket.

On the particular N62 in the video it shows two part chain guide that could self destruct and that is the top suspect that could give enough chain slack that could still run the engine and also cut into the solinoid socket.

I'm very very interested to see what actually happened hope you can look inside soon.
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  #48  
Old 05-07-2020, 04:41 PM
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I think the vanos socket is just fine because it is inside of the chain. My suspission is also the no 7 or that no 16 came loose. But before I have taken it apart I have no clue just guessing.

I dont think chain guide 10 has a mechanical stop it΄s actually quite similar contruction as BRP has on the rotax engines it's the chain that is the stop.

Well I think I have a couple of hours of dissasembly, need to remove bottom pan, cooler front etc... I will try to change the chains and guides with the enginge in the car but I dont know if it is doable, time will tell. The tensioner on passenger side is my biggest concern right know there is not enough room to take it out.
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  #49  
Old 05-07-2020, 07:21 PM
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There has to be enough room to remove bank one tensioner.

The M62 the spacing is bad the AC compressor is in the way.

On closer inspection it does look like the chain does miss the socket. That's very good news.
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  #50  
Old 05-08-2020, 03:43 PM
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Dissasenbled everything in the front this evening, so the V is really accessible know. I think I will remove the generator ac pump and do a not workshop proffessional solution on the timing chain tensioner on bank 1 The mig has to do some work after this operation... If I do that I will save a lot of hours.
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