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I made a mistake on my cam adjuster replacement project and I don't know how to recover, so I'm looking for some advice.
The mistake was that I removed the cam tensioner before rotating the motor to TDC and installing the alignment hold fixture. When I was rotating the engine to TDC, the timing chain skipped on the intake cam side and put it about 90 degrees out of adjustment before I realized what was happening. I thought I could just rotate the intake cam back into position with the timing chain removed, but when I try the intake cam puts up a huge resistance and I'm afraid to put more force into it.
Any tips on what I need to do to realign the intake cam with the crank and exhaust? I'm clearly in over my head at this point lol.
2012 C250 Couple. Spark plugs have been removed as well.
Thanks!
Last edited by PandaDon; Jun 29, 2024 at 09:29 PM.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Hopefully you can move the crank shaft so that none of the pistons are at the top. Do not force if you meet hard resistance. I've not done a timing alignment, but I assume there are timing marks on the cams. Are you following any written procedures?
There are timing marks on the cams, and the intake is almost exactly 90 degrees off from the exhaust.
I don't have a written procedure. I was following youtubes for the timing chain/cam adjuster/tensioner swap and messed up the sequence, so now the job has changed to realigning the camshafts correctly. This is my first major job with a Mercedes, so I'm still trying to figure out what the best resource is. I've seen discussions on WIS and Youcanic, but I could use some help identifying the best resource.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
You need to get a copy of the WIS. The WIS is the electronic shop manual. There are too many documents and procedures to print out for what you are doing, but here are a couple.
Thanks! I've seen a lot of warnings about malware and all sorts of crazy stuff on buying a copy of WIS online. This site looks legit, but I'd be happy to get a recommendation:
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
You are dead in the water until you get this fixed. Search on eBay for WIS/ASRA/EPC. Copies you download will run in a virtual machine on your computer. That's to preserve the activation key for the software. In the future, you should consider getting a membership with @BenzNinja who will also provide a copy of XENTRY, WIS, EPC, and other critical software, and provide remote support if you are going to be working on your car yourself. It is a one-time investment in the most powerful diagnostic tool for your Mercedes. XENTRY not only is the dealer's shop scan tool, but also walks you through diagnostic procedures.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Originally Posted by PandaDon
Thanks! I've seen a lot of warnings about malware and all sorts of crazy stuff on buying a copy of WIS online. This site looks legit, but I'd be happy to get a recommendation:
I have purchased from them in the past before I went the BenzNinja route. I'm not sure how they deliver the WIS software, but they did send me an SSD with the XENTRY and WIS software, and then remoted into my laptop to set everything up. It did take them several hours to configure everything.
You linked to the WIS/ASRA software. EPC is the parts catalog, which is very useful for finding parts and exploded views of the car. That's another $35, I think.
If you have a second car and can wait until you get all the components for a XENTRY system, you should seriously consider BenzNinja. He has a very good reputation on this forum. I recommend this even if you go with just the WIS software now to get your car running.
I appreciate the advice and I'll take a look on ebay, and check out BenzNinja. And you're right about being dead in the water. I'm clearly in need of more info about how to get the cams properly re-aligned.
Sorry to hear that you’ve been fighting this for a whole day. As you know, there are 2 pistons at TDC and 2 pistons at BDC together on a 4 with a flat plane crank. The M271 is an interference engine and that’s what’s got you. It’s good you stopped trying and didn’t just go get a longer cheater. You have valves hitting one of the pistons at TDC on the intake or exhaust stroke.
I’ve learned a lot of things about engines by doing it wrong once, so don’t beat yourself up. There are a number of ways to get out of this, but here’s what I would try.
I’m assuming that your crank has cylinder 1 at (or near) TDC. Rotate your crankshaft 90 degrees and remember which direction you turned it, CW or CCW. Be sure to stop if any resistance is met. All 4 pistons should be half way down in the cylinders and clear of the valves. Now set the cams at the timing marks and install the cam alignment fixture. Turn the crank in the opposite direction to get back to TDC. Stop if there’s any resistance. You’re good to continue what you were doing.
If you do meet resistance, you’ll need to get the WIS and look for camshaft removal and replacement. Remove the cam shafts. Set cylinder 1 to TDC. Then follow the WIS instructions to replace them and retime the engine. Install the cam alignment fixture and go to what you were going to do. There’s no concern with interference using this method, but it’s more involved.
I don’t recommend trying to ”walk” the crank and cams back around to correct timing. There too much chance for damaging valves for me.
I also don’t recommend removing the cylinder head. That comes with a host of other things that have to be removed and reassembled correctly.
Thank you both! I watched some animations on interferrence engines and I now see how trying to re-align the intake cam with the crank at TDC isn't going to work. Today's plan is to follow the advice and get the pistons at mid-stroke and line everything back up. The instruction sets will also help me stay on procedure.
I'll post some picks when I get it back to what I think is the correct alignment.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
I recommend getting a dedicated laptop if you are going forward with getting XENTRY. Here is the one I have (from Amazon) and approved by @BenzNinja . He will send you a new SSD with all the software pre-loaded and provide remote setup, as well as lifetime support. Lifetime support includes remote diagnosis of any problems with any Mercedes you own or may own. The really nice thing about BenzNinja's software is that there are no virtual machines or other "tricks" to make things work. The Mercedes software (XENTRY, WIS, EPC, etc.) is tied to the unique serial number of the network interface controller of your PC. If, for some reason, that gets messed up, BenzNinja will reset it for you to get things working again.
Membership is in a club format with a one-time fee. The only other item you will need is a C4 multiplexer and he will be able to recommend a good one. Most all are clones out of China and there are some good ones and not good ones. You want to stick with the C4 (versus a C3, C5, etc.) with DoIP capability. This will allow him to do custom configurations to add (or disable) features, as well as perform control module software updates. Check on this subforum for his posting.
Thanks for the advice on the laptop. I'm going to see if I can make it through this project with y'all as a resource, and then think about the long-term plan.
Another newbie question, how do I determine whether my engine is a 271.8 or 271.9, so I know which torque spec is correct for the cam adjusters?
Wikipedia and the YouTubes I'm running across are saying the 2012 C250 is the 271.8, but it would be nice to have a more definitive source before I put everything back together.
A recommendation for when you are reinstalling the tensioner: Release it very, very slowly. Too fast, the chain can jump, throwing out the alignment. Then, you have the pleasure of repeating the process. I'm obviously a slow learner and had to do this several times before I realized that everything was correctly aligned and that the release of the tensioner was causing the misalignment. As Odd Piggy recommended, rotate the engine through two full turns to verify everything is correctly aligned.
Thanks for the confirmation, and the advice on reinstalling the tensioner. I've got a few days off starting tomorrow, but I'm in Texas so only working on the car in the early mornings. If I don't run into any more surprises or confusing moments I should have it all put together by Sunday. Fingers crossed.
Hey everyone, just to put a pin in this post, I got everything put back together and I've put a couple of hundred miles on the car with no issues. It was a fairly straightforward project and the only other "mistake" that I made was that I got curious about how the tensioner worked and pushed in in to release the spring, and then had to spend a few hours watching youtube to figure out how to reset it before doing the installation. I now know just a little bit more about what's under the hood of my C250!
Hey everyone, just to put a pin in this post, I got everything put back together and I've put a couple of hundred miles on the car with no issues. It was a fairly straightforward project and the only other "mistake" that I made was that I got curious about how the tensioner worked and pushed in in to release the spring, and then had to spend a few hours watching youtube to figure out how to reset it before doing the installation. I now know just a little bit more about what's under the hood of my C250!
Congratulations! That was quite an ordeal for an introduction to the M271 engine. Yes, I replayed the video below several times, and in the end, I could reset the tensioner in less than a minute.
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