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New member here. Working on a 2012 CLS550, VIN WDDLJ7DBXCA015107. Started having the cold start rattle when the car was 13 years old with 120K miles on it. No issues with any rattling before that. Pulled the timing covers and have the following observations and questions:
The right side intake cam adjuster and tensioner are bad. I’m going to finish working on this side as part of the learning curve before I work on the left side.
The cam adjuster retainer kit I bought off Amazon didn’t fit. User feedback indicated it was 50/50 and the one I had didn’t fit (too big). Ordered a new one from a different vendor and will see what happens. Does anyone have a recommendation for a retainer kit that works on the M278 in case this new one doesn’t fit?
There was no check valve installed behind the tensioners and the kit I ordered off FCP Euro had them in their kit. I’m not sure I want to install these as it seems they’re going to restrict oil flow and I didn’t have any issues with not having a check valve for over 10 years. It also seems to be another failure point in the oil system. Any thoughts?
Thank you to all of the folks who’ve posted the great amount of information on this site.
Have you done the oil pump solenoid mod? You shouldn't have to worry about oil flow to the top end that way. I've checked mine with great results on my Foxwell NT 809BT. I get the ghost codes for oil solenoid and always on split loop cooler pump grounding. I can see live data that oil pressure reads 58-60 psi 2 secs after start up.
If you have not done this I suggest it 100% I've seen the effects on head temps to from the extra oil cooling. I just unhooked mine and made dummy plugs from 2 pin cam shaft sensor extensions I got off ebay.
Plugged the shorter one in to the solenoid and other into the harness end. Just zip tied out of the way of the alternator pully and belt. Took longer to put car on the ramps and take off the belly pan bolts then to do everything else.
I do have a M157 swap from a 2016 I dont think that should matter for check valves. Its just that garbage *** 2 stage oil pump crap for fuel economy lmfao.
I dont understand how a oil solenoid delete would alter the flow back of the cam position systems. I would of course want the check valves to keep the oil on the top of of the engine....and can confirm with 100% accuracy that even with the solenoid delete you can start to get the cam rattle.
I’d consider the check valves a necessary part of the repair, not an optional add-on. Since you’re already in there replacing adjusters and tensioners, it doesn’t make much sense to leave out a known weak point in the oiling system.
The fact that it ran fine for years doesn’t really argue against installing them now — cold start rattle is exactly what the check valves are meant to prevent by keeping oil in the upper galleries after shutdown. They don’t restrict flow in normal operation; once pressure builds, they open and behave like a straight-through passage.
I'm guessing since the engine I have now since the swap is just over 62k (unverified) I've lucked out for chain rattle. Since the oil pressure is almost instantly high in 2 seconds this will aid in chain rattle pressurized. The oil pressure isnt 2 stage high till about 2800-3000k RPMs when mine was kicking in with live data. I do change the oil around the 4k mark. Oil is cheap engines aren't.
Last edited by Desert_benz; Feb 6, 2026 at 07:45 AM.
yes, you do need check valves. They keep the oil in the tensioners so they dont bleed down leading to rattle at startup and extra wear on the adjusters and chain. I did these years ago an it completely stopped any rattle on startup. the car can sit for a month in cold weather and not make a sound. Oil in the top end at startup is a good thing. In that your car has not had then on ten years doesn't mean they should not have been upgraded long ago. Similar to any other neglected item, sure, it can last, but not as well as otherwise.
Well that's good to know. Ill have goodspeed check into putting these in for extra insurance. As this car can sit for 3 and 4 days. This is my non everyday car. I have a pretty stock Evo X so this car is a huge step up!
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