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Noticed a rattle on startup at the weekend. I thought timing chain tensioner and ordered a new one on Sunday evening. Monday morning, longer than usual crank and rattle. Hmmm? Monday afternoon, even longer crank and rattle. Checked the battery voltage with engine running and not running and all was good. Connected code reader; pending P034062. Not happy. Started and stopped the engine a few more times which then triggered the check engine light and the permanent P034062 code. Maybe just the camshaft sensor? Bought a Bosch sensor at the local parts store, installed it, cleared the code, and tried again. No joy; code returned. Need to replace the intake and exhaust camshaft adjusters. Tough night last night deciding whether to throw in the towel and look for a new vehicle or tackle the repair. Watched several YouTube videos. Car has 196K miles. With the age and mileage, paying the dealer or even an independent doesn't really make financial sense. So, it's DIY but even then the parts cost is around $1500 and do I really want this project? Well, I decided this morning that I needed another challenge and bought all the parts. I'll upload pictures of all the fun.
I do have a question for those who have tackled this before. One article I read pointed out that the camshaft locking tool was difficult to install if the camshafts were out of alignment. Can you just move these manually with the camshaft adjusters and the timing chain still installed to allow the tool to seat properly? Does anyone have the locking tool that they would be willing to rent?
When you set it to timing at crank 0 degrees , the timing mark at the cam should line up,(if its off and exh is on just do the intake ), usually the intake cam adjuster is all you need , however with your miles you need to do the chain,and exhaust adjuster they stretch, i bought the tools minus the can holding too for 70.00, the holding tool for cam was cheep to like under 40.00
When you set it to timing at crank 0 degrees , the timing mark at the cam should line up,(if its off and exh is on just do the intake ), usually the intake cam adjuster is all you need , however with your miles you need to do the chain,and exhaust adjuster they stretch, i bought the tools minus the can holding too for 70.00, the holding tool for cam was cheep to like under 40.00
Picked up the Torx100 & camshaft holding tool for a reasonable price. I hadn't originally planned on replacing the chain but it would be foolish not to do so. Just need to shop around for the chain tool. Off to change the water pump & thermostat on the other German money pit so that I can drive it while working on the C250.
Noticed a rattle on startup at the weekend. I thought timing chain tensioner and ordered a new one on Sunday evening. Monday morning, longer than usual crank and rattle. Hmmm? Monday afternoon, even longer crank and rattle. Checked the battery voltage with engine running and not running and all was good. Connected code reader; pending P034062. Not happy. Started and stopped the engine a few more times which then triggered the check engine light and the permanent P034062 code. Maybe just the camshaft sensor? Bought a Bosch sensor at the local parts store, installed it, cleared the code, and tried again. No joy; code returned. Need to replace the intake and exhaust camshaft adjusters. Tough night last night deciding whether to throw in the towel and look for a new vehicle or tackle the repair. Watched several YouTube videos. Car has 196K miles. With the age and mileage, paying the dealer or even an independent doesn't really make financial sense. So, it's DIY but even then the parts cost is around $1500 and do I really want this project? Well, I decided this morning that I needed another challenge and bought all the parts. I'll upload pictures of all the fun.
I do have a question for those who have tackled this before. One article I read pointed out that the camshaft locking tool was difficult to install if the camshafts were out of alignment. Can you just move these manually with the camshaft adjusters and the timing chain still installed to allow the tool to seat properly? Does anyone have the locking tool that they would be willing to rent?
curious if this is your first repair for this? Had it done at 60k and wondering how they hold up now that I’m at 145k
Noticed a rattle on startup at the weekend. I thought timing chain tensioner and ordered a new one on Sunday evening. Monday morning, longer than usual crank and rattle. Hmmm? Monday afternoon, even longer crank and rattle. Checked the battery voltage with engine running and not running and all was good. Connected code reader; pending P034062. Not happy. Started and stopped the engine a few more times which then triggered the check engine light and the permanent P034062 code. Maybe just the camshaft sensor? Bought a Bosch sensor at the local parts store, installed it, cleared the code, and tried again. No joy; code returned. Need to replace the intake and exhaust camshaft adjusters. Tough night last night deciding whether to throw in the towel and look for a new vehicle or tackle the repair. Watched several YouTube videos. Car has 196K miles. With the age and mileage, paying the dealer or even an independent doesn't really make financial sense. So, it's DIY but even then the parts cost is around $1500 and do I really want this project? Well, I decided this morning that I needed another challenge and bought all the parts. I'll upload pictures of all the fun.
I do have a question for those who have tackled this before. One article I read pointed out that the camshaft locking tool was difficult to install if the camshafts were out of alignment. Can you just move these manually with the camshaft adjusters and the timing chain still installed to allow the tool to seat properly? Does anyone have the locking tool that they would be willing to rent?
About to tackle the job this weekend. Any advice or specific videos/articles I need to read? I have the locking tool but not a chain rivet installer. Is that really required? Thanks in advance.
About to tackle the job this weekend. Any advice or specific videos/articles I need to read? I have the locking tool but not a chain rivet installer. Is that really required? Thanks in advance.
Here are a few of the videos I watched. The first is the best for all of the steps but there is no commentary. The second is an excellent explanation of the problem with really detailed steps to split and remove the chain. The third is not quite as detalied as the other two but it's always useful to see as much as possible. I found you don't need to remove as many components as the first two videos show, especially the coolant system items. You can leave parts connected and pushed out of the way. I've started the disassembly work but haven't yet replaced the camshaft adjusters; I plan to do that this weekend. By the way, in addition to the locking tool you will need the special T100 Torx socket to remove the adjusters. I bought a chain kit from eBay but I'm having second thoughts about replacing the chain. I have a facelift C250 and the chain kit tool doesn't fit exactly (same comments on second video). The chain splitter will work but not the temporary master insert to feed in the new chain or the tool inserts to press on the new link and compress the pins. I know I really should replace the chain but my gut is telling me once I start I might end up going down a path I didn't want to travel.
Here are a few of the videos I watched. The first is the best for all of the steps but there is no commentary. The second is an excellent explanation of the problem with really detailed steps to split and remove the chain. The third is not quite as detalied as the other two but it's always useful to see as much as possible. I found you don't need to remove as many components as the first two videos show, especially the coolant system items. You can leave parts connected and pushed out of the way. I've started the disassembly work but haven't yet replaced the camshaft adjusters; I plan to do that this weekend. By the way, in addition to the locking tool you will need the special T100 Torx socket to remove the adjusters. I bought a chain kit from eBay but I'm having second thoughts about replacing the chain. I have a facelift C250 and the chain kit tool doesn't fit exactly (same comments on second video). The chain splitter will work but not the temporary master insert to feed in the new chain or the tool inserts to press on the new link and compress the pins. I know I really should replace the chain but my gut is telling me once I start I might end up going down a path I didn't want to travel.
When you remove the alternator you will see a plug on the side of the lower timing cover (see red circle). Put a screwdriver or a pick through the middle of this plug then pull it out. The tensioner is behind this plug (19mm). I just removed the four alternator mounting bolts and left the electrical connections in place. No need to completely remove it.
When you remove the alternator you will see a plug on the side of the lower timing cover (see red circle). Put a screwdriver or a pick through the middle of this plug then pull it out. The tensioner is behind this plug (19mm). I just removed the four alternator mounting bolts and left the electrical connections in place. No need to completely remove it.
Thanks for the extra pictures. They helped understand a bunch.
Got the valve cover off and the plug removed. Looks like the intake adjuster and chain have been replaced before so I am going to leave the chain alone. Is there a special sequence to install the tensioner, like crank to a different timing position and torque? I seem to remember something like that but can't find it anymore. How is the progress on your project?
Thanks for the extra pictures. They helped understand a bunch.
Got the valve cover off and the plug removed. Looks like the intake adjuster and chain have been replaced before so I am going to leave the chain alone. Is there a special sequence to install the tensioner, like crank to a different timing position and torque? I seem to remember something like that but can't find it anymore. How is the progress on your project?
After you screw in the new tensioner, hold the intake camshaft with the T100 torx socket and rotate the crankshaft opposite to the normal rotation by 15 degrees. You will hear a click which means the spring in the tensioner has been released and the tensioner is pushing against the chain. I have most of the parts off the front of the engine but the honey-do list pre-empted any further progress this weekend.
After you screw in the new tensioner, hold the intake camshaft with the T100 torx socket and rotate the crankshaft opposite to the normal rotation by 15 degrees. You will hear a click which means the spring in the tensioner has been released and the tensioner is pushing against the chain. I have most of the parts off the front of the engine but the honey-do list pre-empted any further progress this weekend.
In the exact same predicament. The honey's car battery died, had to chain saw some trees... you know... the usual. Looks like next weekend is C250 weekend.
In the exact same predicament. The honey's car battery died, had to chain saw some trees... you know... the usual. Looks like next weekend is C250 weekend.
All done. Works great. BUT... funny thing about the P034062 code... sometimes it really DOES mean the sensor is bad. Got the whole thing back together and fired it up. Long start (but not as long) and initial chain rattle (first time oil pressure in all the components), then the CEL. Bummer. Shut down, clear code, restart (long start but not as noisy), P034062 comes back. Turns out the PO had changed out the intake cam position sensor with some weird aftermarket sensor that did not even look correct and would not fit in the exhaust sensor spot when I tried to swap them for troubleshooting. Ordered a new one and installed. No more P034062 and starts up immediately with no chain rattle!
I still feel the cam phaser/adjuster was the cause of the rattle (one was original and one new with a new chain... why didn't the PO change both?!!) but I should have done the cheap and easy thing by changing out the sensor first. Lesson learned.
Oh, and I have an almost brand new cam locking tool for sale now. $50.
Last edited by mildenbenz; Jun 24, 2022 at 08:07 AM.
All done. Works great. BUT... funny thing about the P034062 code... sometimes it really DOES mean the sensor is bad. Got the whole thing back together and fired it up. Long start (but not as long) and initial chain rattle (first time oil pressure in all the components), then the CEL. Bummer. Shut down, clear code, restart (long start but not as noisy), P034062 comes back. Turns out the PO had changed out the intake cam position sensor with some weird aftermarket sensor that did not even look correct and would not fit in the exhaust sensor spot when I tried to swap them for troubleshooting. Ordered a new one and installed. No more P034062 and starts up immediately with no chain rattle!
I still feel the cam phaser/adjuster was the cause of the rattle (one was original and one new with a new chain... why didn't the PO change both?!!) but I should have done the cheap and easy thing by changing out the sensor first. Lesson learned.
Oh, and I have an almost brand new cam locking tool for sale now. $50.
That's great news it's all fixed. When the code first appeared I swapped out the intake cam position sensor hoping, just hoping that was the problem. Sadly, no success. Honey-do list seems to be longer than before and the temperatures haven't dropped off much so no progress. May have to take an extra vacation day next weekend and finish up the work.
Finally managed to spend some time over the weekend replacing the camshaft adjusters. The intake adjuster was definitely the problem. In the picture, the lines on the camshaft adjuster, the camshaft itself, and the arrow on the camshaft bracket should all line up. As the picture shows, the camshaft mark was out of alignment (timing retarded?). The two lines and the arrow all lined up correctly on the exhaust camshaft. The actual task wasn't too difficult once all the parts had been removed (btw, I hate the hard pipe between the reservoir and power steering pump). Unfortunately, I didn't have the correct seal for water pipe on the back side of the upper timing cover so I couldn't put it all back together. The old seal was flat and I didn't want to risk a potential water leak. Hopefully I can purchase the seal locally and complete the job at the weekend.
Great post, and thanks for all the links for videos. Mildenbenz, still have that locking tool for sale? I'm at almost 190k, and am doing my head gasket, and decided to do the timing chain as well since I'm well over due. thanks for pics too, alynch.
Not the conclusion to the task that I had hoped. Installed the the chain tensioner then rotated the engine a couple of times to check that everything was correct prior to reassembly. Despite the crankshaft pulley showing top dead center, both the intake and exhaust camshafts appear to be off. Looking at the arrows it appears that the intake camshaft adjuster is one tooth off. So, I removed the chain tensioner, held the intake camshaft with a wrench, and unscrewed the bolt on the adjuster. I must have allowed the whole assembly to move because after I moved the camshaft adjuster one tooth, I looked down and saw that the crankshaft had moved. I tried various things to try and bring it all back into alignment (some of them, I admit, were not too smart) but no success. I had to back away before permanently damaging anything. What should have been a couple of hours' work to reassemble turned out to be several steps back. Looks like I'll need to remove both camshaft adjusters, rotate the crankshaft back to TDC without dropping the chain, then re-install adjusters.
Intake Camshaft
Exhaust Camshaft
Camshaft Adjuster Arrows
TDC Movement
Originally Posted by alynch
Finally managed to spend some time over the weekend replacing the camshaft adjusters. The intake adjuster was definitely the problem. In the picture, the lines on the camshaft adjuster, the camshaft itself, and the arrow on the camshaft bracket should all line up. As the picture shows, the camshaft mark was out of alignment (timing retarded?). The two lines and the arrow all lined up correctly on the exhaust camshaft. The actual task wasn't too difficult once all the parts had been removed (btw, I hate the hard pipe between the reservoir and power steering pump). Unfortunately, I didn't have the correct seal for water pipe on the back side of the upper timing cover so I couldn't put it all back together. The old seal was flat and I didn't want to risk a potential water leak. Hopefully I can purchase the seal locally and complete the job at the weekend.
Great post, and thanks for all the links for videos. Mildenbenz, still have that locking tool for sale? I'm at almost 190k, and am doing my head gasket, and decided to do the timing chain as well since I'm well over due. thanks for pics too, alynch.
Yes still have the tool. PM me if you would like it.
Just to close everything out and perhaps help someone who may experience the same problem. I finally managed to complete this project yesterday. Pressures of work and frustration caused the delay. I had tried several times over the last few months to finish the job, but the crankshaft ended up off TDC every time. Eventually, I realized the process of releasing the chain tensioner was causing the timing to skip. To release the tensioner, rotate the crankshaft backward until you hear a click, then rotate the engine forwards, and the tensioner extends. In my case, I found if you rotate forwards too quickly, the tensioner jumps out and causes the chain to jump. If you rotate forwards slowly, the tension in the chain gradually increases, and the crankshaft and camshafts all remain in alignment. With hindsight, it seems obvious, but frustration has a habit of clouding common sense. It was such a relief to rotate the engine with all the timing marks lined up. Another couple of hours and the engine was purring like a kitten (I think it's even quieter than before, but who knows).
As an aside, the car's been off the road for almost five months, and I had forgotten just how good a car it really is and how well it drives. Even with 198,093 miles, it feels smooth, solid, and a pleasure to drive again.
Originally Posted by alynch
Not the conclusion to the task that I had hoped. Installed the chain tensioner then rotated the engine a couple of times to check that everything was correct prior to reassembly. Despite the crankshaft pulley showing top dead center, both the intake and exhaust camshafts appear to be off. Looking at the arrows it appears that the intake camshaft adjuster is one tooth off. So, I removed the chain tensioner, held the intake camshaft with a wrench, and unscrewed the bolt on the adjuster. I must have allowed the whole assembly to move because after I moved the camshaft adjuster one tooth, I looked down and saw that the crankshaft had moved. I tried various things to try and bring it all back into alignment (some of them, I admit, were not too smart) but no success. I had to back away before permanently damaging anything. What should have been a couple of hours' work to reassemble turned out to be several steps back. Looks like I'll need to remove both camshaft adjusters, rotate the crankshaft back to TDC without dropping the chain, then re-install adjusters.
Hello all, it's been some years since this thread was active, so I'm hoping that you all are still around. @alynch , I'm nearby in Destin.
I just acquired a 2014 C-250 and I have been trying to get it running. I checked the codes and found the same as you guys, P034062, comparison fault. I'm going to try the camshaft sensor first, and maybe I'll get lucky, but I doubt it. This car has 132k on the Odometer, and I don't think it was well cared for. So I'm assuming that the PO didn't want to pay for this repair and left it. I'm about to embark on the same task as everyone else.
I have never done this before, but I'm not undeterred. Just uneducated about what needs to be done. I have used FCP Euro but I don't know what kind of kit and equipment I'm looking for. Is there a kit or part number I should be looking for? Do I need to replace the chain and the adjusters too?
I read the posts above about the Torx 100 tool, so I'll be sure to look for that. Since there's a lot of other stuff that will need to be disconnected, what else should I plan on doing while I'm in there? Water pump? Head and intake gaskets, I assume.
What else am I missing? Considering how long it took you guys to get this done, I would say that I'm in good company. There's no way this is going to be quick, so I might as well plan ahead and do it properly.
Last edited by gshockxcc; Sep 3, 2025 at 06:50 PM.
Reason: Punctuation, Links
There is about a 1% chance that the camshaft position sensor is bad, but since it’s very easy to access, go ahead and do it anyway. You don’t have to buy MB branded sensors, but do get Bosch sensors with the same manufacturer part number that is on the Mercedes originals.
I have seen kits containing camshaft adjusters, timing chain, and chain tensioner on eBay. I’m not a fan of no name parts, so I would suggest using FCP Euro as you mentioned. There is a thread on resetting the chain tensioner. It’s time consuming and can be frustrating. I recommend just getting a new one. The timing chains are not robust, especially if the car was not well maintained. It would be much better to end this process with a new chain that would run trouble free for 100,000 miles.
Yeah, I agree with you on the comment about no-name parts. I have always found that it's better to spend a bit more and get quality parts that will last. I'll get with FCP and get the full timing chain kit. I have been watching the videos that alynch posted, and they make it pretty straightforward what needs to be done. I still have some research to do, and it will take me a while to procure all the parts. I need to get the vehicle into the driveway and secured, then I'll start tearing into it and getting it ready.
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