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Inspecting Balance Shaft Sprocket

1199 Views 47 Replies 9 Participants Last post by  FUNkleBENZ
Has anyone used a bore-scope to diagnose a worn balance shaft sprocket? My engine on this 2007 E350 is outside of the affected range, but over the last couple of thousand miles of driving (total miles on the car are about 210,500) I've gone from just one code (DTC 1208 aka P0016, right side intake camshaft retarded) up to two codes (add DTC 1200 aka P0017, right side exhaust camshaft retarded) and now I'm at three codes (add DTC 0063 aka P0024, left side exhaust camshaft retarded). I'm looking for some method of diagnosis to determine if my timing chain needs to be replaced or if I've got to go all the way and replace the balance shaft etc. The bulletin that describes how to diagnose the bad balance shaft sprockets for the affected range of engines does say that in rare cases, the timing chain is the cause.

My thought process is to have the right side cover on the front of the camshafts pulled off, and then snake the bore-scope down the timing chain into the case to get a view and pictures of the sprocket.

If I can confirm the sprocket is fine, that leaves the timing chain, the rails, and the chain tensioner.
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Maxbumpo,
Have you done a visual static cam position check? Takes about 15 minutes.

I've also heard faults can be caused by faulty cam sensors as well, but I dunno your particular situation.
I'd be interested as well if a borescope can be utilized to scope out balance shaft sprocket condition.

My 2006 E350 is within the bad range, but it's still fine with 146K miles. They say only 10-30% of engines within the bad range are actually faulty, as MB apparently had several suppliers of the sprockets so not all had the manufacturing process wrong. 馃
 

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Has anyone done this? From what I鈥檝e seen in M272 disassembly videos, there鈥檚 no path for a borescope to the balance shaft sprocket.

Sixto
05 E320 wagon 197K miles
 

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I believe those sensors go bad too. Lots of times those end up getting replaced when the engines are in the range and it's really the balance shaft. As you're outside the range, it's probably just the sensors, but it could also be the chain too as you're up there in mileage.
 

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Discussion Starter · #5 ·
Maxbumpo,
Have you done a visual static cam position check? Takes about 15 minutes.
Yes, right side were slightly off, left side were perfect. "Slightly off" means that the stamped circle on the pulse wheel was still fully in the hole and not even touching the outer boundary, but not perfectly centered. Did this just a couple or three months ago.

I've also heard faults can be caused by faulty cam sensors as well, but I dunno your particular situation.
I'd be interested as well if a borescope can be utilized to scope out balance shaft sprocket condition.
I've heard that too, and so when I was just having the first two codes on the right side bank, I swapped all the sensors from left to right and vice versa, to see if the problem would follow the sensor. The problem did not follow the sensors, so I think that rules out faulty sensors.
 

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Yes, right side were slightly off, left side were perfect. "Slightly off" means that the stamped circle on the pulse wheel was still fully in the hole and not even touching the outer boundary, but not perfectly centered. Did this just a couple or three months ago.



I've heard that too, and so when I was just having the first two codes on the right side bank, I swapped all the sensors from left to right and vice versa, to see if the problem would follow the sensor. The problem did not follow the sensors, so I think that rules out faulty sensors.
OK, before digging deep into the motor, could it possibly be one or two of the cam adjusters aren't working properly?
Maybe there's a way to check this with OBD-II live scan?
With that many miles, it might be worthwhile checking the chain tensioner too. I'm certainly no expert, but as you've been doing, I would rule out the easier fix stuff first.

I'm following this thread, as this might eventually be something I'll have to face on my M272. I was pulling some funky codes relating to non oxy sensor pre-heat etc that didn't make sense; however, replacing the ECU solved that one. Why did Mercedes think putting the ECU on top of the motor, subjected to high heat and vibration was good engineering?

At least you've gotten +200K out of the motor so far. With that many miles, some degree of chain and tensioner wear might be expected.
 

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Discussion Starter · #7 ·
A little history of this car. I purchased it cheap cheap this summer with about 206k miles and a 'bad transmission'. Lots of other little things wrong, from broken sun visors to broken intake manifold flaps. I think I'm the 7th or 8th owner. No service history. It did have a sticker in the windshield from Wal-Mart saying that the next oil change was due at 203k miles or somesuch. Lots of deferred maintenance. Gradually I've sorted a bunch of problems and restored the car to daily driver status. This engine problem is the last major and possibly expensive problem to resolve.

When the first code happens (DTC 1208 aka P0016, right side intake camshaft retarded) the live data reading for that camshaft adjuster will freeze (it freezes at 36.20 degrees).
 

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Discussion Starter · #8 ·
OK, before digging deep into the motor, could it possibly be one or two of the cam adjusters aren't working properly?
Maybe there's a way to check this with OBD-II live scan?
Yes, that's also a possibility. Other than removal and inspection, I haven't found a way to diagnose other than via the codes.

With that many miles, it might be worthwhile checking the chain tensioner too. I'm certainly no expert, but as you've been doing, I would rule out the easier fix stuff first.
Agreed, chain tensioner is also on the list.
 

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Discussion Starter · #9 ·
Also found this car was on the service bulletin list for faulty camshaft adjusters (allowed engine oil to seep through electrical connector and cause faulty readings) and the campaign fix was to install pig-tail / jumpers in between the engine harness and the camshaft adjusters. That fix has been completed prior to my purchase.
 

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Discussion Starter · #10 ·
Looking at pictures and diagrams, it seems to me that there is a narrow gap between the timing chain and the 'throat' for the timing chain in the head. Theoretically, a bore scope that is small enough and long enough could be snaked down this opening and have a good view of the gear on the balance shaft. I'd like to get confirmation that this is possible. An independent garage near me, owned by a friend, is willing to give it a go if I can provide enough info for them. I'm trying to figure out what needs to be removed in order to get enough access.
 

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Discussion Starter · #11 ·
I'm also considering a very red-neck option, carefully drilling a hole in the timing case right above the gear / sprocket, and inserting the bore scope through the hole. Get the pix, decide if balance shaft sprocket failure is the issue. If that sprocket is OK and not my problem, seal up the hole and proceed with other diagnosis / repairs.
 

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Discussion Starter · #12 ·
Another option: drop the lower oil pan and check for metal debris from failing sprocket. Presence of debris would be a pretty good sign that the sprocket is failed, but not definitive like a visual check.
 
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Never tried snaking a borescope into the engine. I doubt that you can make it to the balance shaft because of the chain guides.

As others have mentioned, check the position of the cams by removing the adjusters. If they are off, then expect a stretched or worn chain. That will require the engine to be opened up. No quick fixes, no Marvel's Mystery oil.
 

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I installed a magnetic oil drain plug to get some indication. So far, no metal shards at oil changes, and Left vs Right side cam positions are OK at 305 deg. 馃馃

Only CEL was from the faulty ECU, but that was fixed with an MB factory re-man I had to have MB install due to it being a theft controlled part. ~$1,600 all-in. But, considering I only paid $5,900 for this handsome car 7 years ago; it owes me nothing at this point. The 'potential' balance shaft issue makes these cars extremely affordable; and a pre-purchase static cam position check as in post #2 can provide some reassurance the issue isn't imminent.
 

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Discussion Starter · #15 ·
Never tried snaking a borescope into the engine. I doubt that you can make it to the balance shaft because of the chain guides.

As others have mentioned, check the position of the cams by removing the adjusters. If they are off, then expect a stretched or worn chain. That will require the engine to be opened up. No quick fixes, no Marvel's Mystery oil.
Neighbor used to be a mechanic in a shop that serviced a lot of British cars from the 60s and 70s. He told about one particular model, I think it was a Jag, that suffered some failure on the engine that if you repaired it 'by the factory service manual' you were supposed to pull the engine to get at this part and fix the problem. Classic story of the part costing $10 and the labor for the repair costing $500 or somesuch, and this part failure was pretty common and occurred on a regular basis. Car would be tied up in the shop for a day or two while R and R the engine. One of the mechanics decided to just cut a hole in the firewall under the dash, do the repair with the engine still in the car, and then patch up the hole. His method took less than an hour. The car owners were thrilled with the lower cost and speed, as long as they never pulled that carpet back and saw the patched up hole...

Point of the story: Before I pull the engine and pull off the timing case cover to inspect the sprocket, I'd like to have a little more to go on. Maybe a bore scope is not that answer, I'm hoping to determine that it is, maybe someone on this forum has been there and done that and will share the knowledge here.
 

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Best wishes in your pursuits. Don't you think that someone would have already done that by now? This problem began showing up on vehicles 15 years ago.

In another post, there is talk about aliens from the Andromeda galaxy who had special rays that would pressurize a cooling system. Maybe they have a special ray for the balance shaft inspection? Worth a try...
 

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Discussion Starter · #17 ·
Best wishes in your pursuits. Don't you think that someone would have already done that by now? This problem began showing up on vehicles 15 years ago.
That's exactly what I'd like to know, 15 years is a long time and technology and methods have advanced in that time.

In another post, there is talk about aliens from the Andromeda galaxy who had special rays that would pressurize a cooling system. Maybe they have a special ray for the balance shaft inspection? Worth a try...
Ha ha you are so funny.
 

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Discussion Starter · #18 ·
Here's some pictures I took last fall in October, car probably had about 209k miles at this point.
Here's the right side exhaust camshaft pulse wheel as scene through the hole for the camshaft sensor, crankshaft set at approximately 305 degrees. I say approximately because the mark on the timing case used to line up the crankshaft damper is set back enough and difficult enough to see that it is very hard to be precise in setting the crankshaft exactly at 305 degrees.
Automotive tire Motor vehicle Automotive wheel system Font Auto part



This is the right side intake camshaft pulse wheel with the crankshaft set at ~305 degrees.
Automotive tire Motor vehicle Automotive lighting Rim Automotive wheel system


Finally, for reference, I took a picture of the left side intake with the crankshaft set at ~305 deg. This looks like it is not exactly centered but is just a bit retarded, just a hair.
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Because the exhaust are gear-driven from the intake, it's only necessary to compare intake L vs R. Yours actually seem OK to me, but here's mine recently for comparison. No faults. Sorry, not great shots but I'm wondering if your problem(s) are related to cam adjusters?? Sure would be an easier fix.

 

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Discussion Starter · #20 ·
Because the exhaust are gear-driven from the intake, it's only necessary to compare intake L vs R. Yours actually seem OK to me, but here's mine recently for comparison. No faults. Sorry, not great shots but I'm wondering if your problem(s) are related to cam adjusters?? Sure would be an easier fix.
Thanks for comparison pix, so you don't get any DTCs / CEL?

I'm thinking that with over 200k miles and the engine is outside of the range of engines that MB published, the problem could be something other than the balance shaft gear wearing out. A stretched timing chain is a good candidate to cause nearly identical problem. As you pointed out, the cam adjusters might also be a cause, and I've found one post where a guy simply replaced the chain tensioner and solved the problem. Other problems are the solenoid magnets and the sensors. I've swapped around the magnets and the sensors and the problem stayed with the right side intake camshaft, so I'm pretty sure that the problem is not a bad sensor or bad magnet.

The car runs great. There is an engine whine / engine growl that I can't quite fully resolve (new motor mounts, transmission mount and new flex discs made a HUGE difference in reducing that noise).

Power drops off just a bit with I get the DTC 1208 for the right side intake camshaft (retarded) and the live data stream from that sensor freezes at 36.20 degrees. I think this is a big clue but I've not yet found definitive information that this means the adjuster is bad.

Perhaps I'm going to have to pull the right bank valve cover, remove the adjuster, and while I'm there I can figure a way to snake a borescope down to get a good look at the balance shaft gear.
 
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