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the tsb (technical service bulletin) is included in the post..
Use lastvin or vindercoderz, plug in your vin and you see your engine serial number.
there are like 4 revisions to the tsb... Took them a while to get this right
Sorry to revive an old thread here, but I’m struggling to find an answer to this anywhere. I ordered both the 278050400 and 2780503300 for my motor, and my bore has no visible step inside. Also, a 5/16 (~8mm) drill bit will not fit into the bore - so in theory I should use the non-stepped valve. Trouble is, it doesn’t go in even any bit into my cylinder head, as if it’s too big. The stepped valve will, but it’s quite obviously loose in there and incorrect. I’ve tried putting the valve in the freezer to shrink it some, but that hasn’t helped. Anyone else face this?
Sorry to revive an old thread here, but I’m struggling to find an answer to this anywhere. I ordered both the 278050400 and 2780503300 for my motor, and my bore has no visible step inside. Also, a 5/16 (~8mm) drill bit will not fit into the bore - so in theory I should use the non-stepped valve. Trouble is, it doesn’t go in even any bit into my cylinder head, as if it’s too big. The stepped valve will, but it’s quite obviously loose in there and incorrect. I’ve tried putting the valve in the freezer to shrink it some, but that hasn’t helped. Anyone else face this?
it’s good that these threads don’t pop up all the time or people might think that indicates a problem. Glad it is here to hopefully bring us together to help you.
so where I show the valve in my picture above before it is pressed in I honestly cannot remember if I had to use force to get it there before using the press. I may have even started pressing it in and removed it just to take a picture. I honestly don’t know. I was definitely a little worried with the press because it did take some effort because it is supposed to be a tight fit.
I can’t speak to the size of the bore receiving the valve because I didn’t measure it, and it was obvious to me which valve would work in my instance.
since they sent you a kit, I’m assuming you tried both of the smaller check valves?
There’s gotta be a video online showing someone inserting this. And I might also check with AI these days.
sorry, I can’t be of more help
I just checked my old pictures and I don’t have anything else that might be of help but it did remind me that Mercedes changed the finish of the cam caps because the rough surface would not adhere well and that is what caused these to leak in general. So don’t be afraid to either rough that surface up back near shiny or buy new covers. If you’re using Mercedes sealant, make sure it is fresh and to abide by the curing times which can be up to a week if it’s a low humidity cool place. I used Reinzosil instead because I’ve had the Mercedes sealant not be fresh and fail too many times which it did for me in this instance when it was warm humid and left to cure.
Last edited by Baltistyle; Mar 20, 2026 at 06:39 PM.
it’s good that these threads don’t pop up all the time or people might think that indicates a problem. Glad it is here to hopefully bring us together to help you.
so where I show the valve in my picture above before it is pressed in I honestly cannot remember if I had to use force to get it there before using the press. I may have even started pressing it in and removed it just to take a picture. I honestly don’t know. I was definitely a little worried with the press because it did take some effort because it is supposed to be a tight fit.
I can’t speak to the size of the bore receiving the valve because I didn’t measure it, and it was obvious to me which valve would work in my instance.
since they sent you a kit, I’m assuming you tried both of the smaller check valves?
There’s gotta be a video online showing someone inserting this. And I might also check with AI these days.
sorry, I can’t be of more help
Really appreciate your response. I ordered both valves, the stepped and non-stepped, and unfortunately the fit seems to be backwards. I don't have a stepped bore, but the stepped valve fits loosely - which I assume is incorrect. The non-stepped valve won't even slightly slide into the bore, but should be the one that fits. The only videos I've seen online skip straight to the valve already in place, or show it sliding in easily (the official Mercedes video on YouTube).
I tried AI but it gives me nonsensical answers, starting talking about a third valve variant that doesn't exist.
My only other thought is to try and carefully heat up the head and try the freezer trick with the valve, but I'm surprised it's this much trouble.
Since I bought the kit from fcp, it came with two of each because I did both sides. I remember feeling the same way as you in that the stepped valve was not right but initially fit better. I passed my tool along to a random member for free with my extra parts so cant take a pic even to compare the stepped part. I can look to see who I sent that to and maybe they help out. You are correct that its not the stepped valve.
Anyway you can contact who you purchased from. If it was fcp, they are very knowledgeable. Are they OE parts?
DO NOT heat the head. The freezer trick is a good one. Also, you have not mention if you tried the press at all just to get a feeling of the actual resistance. In that the "blunt" end sits in there without holding it, it might be fine.
and thinking about it, I remember the straight valve being tight and thought I should use the stepped valve, but did not.(be careful here and double check as per my post below)
Last edited by Baltistyle; Mar 21, 2026 at 07:19 AM.
and posting separate so you see this. Your "strait" valve DOES NOT look like the valve in the video, or on the fcp website.... I would NOT try pressing it until figuring that out.
Theirs show a clearly thinner part that inserts, a small step (versus the bulbous flared end of the other valve). Yours seems like its all the same diameter along the length.
video FCP
yours
Last edited by Baltistyle; Mar 21, 2026 at 07:20 AM.
Since I bought the kit from fcp, it came with two of each because I did both sides. I remember feeling the same way as you in that the stepped valve was not right but initially fit better. I passed my tool along to a random member for free with my extra parts so cant take a pic even to compare the stepped part. I can look to see who I sent that to and maybe they help out. You are correct that its not the stepped valve.
Anyway you can contact who you purchased from. If it was fcp, they are very knowledgeable. Are they OE parts?
DO NOT heat the head. The freezer trick is a good one. Also, you have not mention if you tried the press at all just to get a feeling of the actual resistance. In that the "blunt" end sits in there without holding it, it might be fine.
this is the video I watched. https://www.youtube.com/watch?v=W7Z3Nqlc8gY
and thinking about it, I remember the straight valve being tight and thought I should use the stepped valve, but did not.(be careful here and double check as per my post below)
I bought all of my parts from AutoHausAZ, looking at the FCP parts they’re exactly the same plus I ordered new tensioner bolts and six new cam magnet bolts.
Everything is Genuine Mercedes except for the valve press which is Baum. I can’t even try the press because the valve won’t go in far enough for the press to even fit over it. It appears as though the valve needs to be most of the way in and the press pushes it the last 20% (even in that video, that’s the same one I’ve been watching). The stepped valve will go in that far, but it’s definitely not right for the application.
Do test the tired VVT phasers stay locked while you are inside the timing cover.
Rotate crank CW 2x turns listen for a snap forward.
My statement is in regards to the check valves keeping the tensioners fed at shutdown so there is no more rattle on startup from the chain. I occasionally had a half second rattle when I bought the car and if it sat. After I did check valves and tensioners, Ive never once had a rattle on start no matter how long the cars sits (even a month in the cold weather). Rattle from phasers is a different ball of wax.
My statement is in regards to the check valves keeping the tensioners fed at shutdown so there is no more rattle on startup from the chain. I occasionally had a half second rattle when I bought the car and if it sat. After I did check valves and tensioners, Ive never once had a rattle on start no matter how long the cars sits (even a month in the cold weather). Rattle from phasers is a different ball of wax.
I am glad adding the missing secondary check-valves to the tensioner built-in check-valve further helped out.
My wake up call was when my new engine rattled at 15kMi with ALL factory check-valves at such low mileage... the ordering dealer was entirely helpless - I then realized this Benz setup was special.
The startup rattle is not the trouble maker here... Driving with limited oil pressure is what locks & unlocks the phasers to wears them out, not startups.
Low mileage hardware can rattle...
Unlocked phasers can rattle...
Flat tensioners can rattle...
Loose reluctors light up CEL...
I really don't see how the missing secondary check-valve helps the secondary chain tensioners own internal check-valve.
External ball-on-spring check-valve does help refill the phasers sooner with early aerated oil mix... The spring tension KEEPS OIL AWAY FROM TENSIONERS until phasers have pressure built-up.
Of course anything does help: the missing 50¢ parts are better on board than left out - This begs the questions:
-- What were MB engineers really trying to acomplish with this whole setup ??
-- Anything else we should do ??
Last edited by CaliBenzDriver; Mar 22, 2026 at 01:38 AM.
Hey y'all, I'm with you on the timing check valve install - it's a relatively simple process, but make sure you use the correct gasket and torque the valve properly to avoid any engine issues down the road. Also, keep in mind that with the newer 4MATIC engines like on my '23 C 43, there are slight variations in the install procedure so be sure to consult the factory manual or online resources specific to your model.
No more rattling at cold start for me - luckily I was able to sneak the driver side cam cover off without removing the oil filter housing also. Made it a much simpler job. The driver side check valve slid in with ease, don't know why the passenger side gave me so much trouble. But all worth it in the end, I can't tell if it's placebo but the motor feels much stronger at pick up. No cover leaks or magnet leaks either now. This is on a '13 SL550 with an M278, but has the oil cooler lines in a similar fashion to the M157.
Last edited by ljuliano; Mar 26, 2026 at 07:57 PM.
Pretty great you didn’t have to remove the oil filter to remove that side. Was there no dowel pin in the bottom right corner when looking at the engine from the front?
No more rattling at cold start for me - luckily I was able to sneak the driver side cam cover off without removing the oil filter housing also. Made it a much simpler job. The driver side check valve slid in with ease, don't know why the passenger side gave me so much trouble. But all worth it in the end, I can't tell if it's placebo but the motor feels much stronger at pick up. No cover leaks or magnet leaks either now. This is on a '13 SL550 with an M278, but has the oil cooler lines in a similar fashion to the M157.
Congrats for completing your upgrade.
The camshafts precise timings are essential.
There best shouldn't be any slop to introduce camshaft position errors.
Steady tensioners with good pressure are able to hold back the short chains against camshaft kickbacks.
Last edited by CaliBenzDriver; Mar 26, 2026 at 09:16 PM.
Pretty great you didn’t have to remove the oil filter to remove that side. Was there no dowel pin in the bottom right corner when looking at the engine from the front?
Glad it all worked out for you.
All the dowel pins were in place, I had to remove the cam magnet that was between the cover and the oil filter for it to be able to clear. It was incredibly tight, but I found just the right angle and it popped out. I was very, very close to removing the oil filter housing but very happy to have avoided that whole ordeal.
14 E63, 05 E55, 03 Evo 8, 08 F250, 06 R6R, 92 Talon TSI, and instability
Originally Posted by ljuliano
All the dowel pins were in place, I had to remove the cam magnet that was between the cover and the oil filter for it to be able to clear. It was incredibly tight, but I found just the right angle and it popped out. I was very, very close to removing the oil filter housing but very happy to have avoided that whole ordeal.
I explained that this was possible previously in another post and was called a flat out liar.
I truthfully have been considering creating an only fans account to put a video of how to do it behind a paywall.
I explained that this was possible previously in another post and was called a flat out liar.
I truthfully have been considering creating an only fans account to put a video of how to do it behind a paywall.
lol, nobody called you a liar. I mentioned in the M157 engine with the dowel pin the engine side or cover would get the cover stuck between the pin and the turbo and that’s why oil filter has to come off. or that the magnet coming out is doable but tight but going in is a little bit shady but I’d not grind the housing.. This is not that engine…. This makes me wonder if the neck of the turbo is different or clocked slightly different here.
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
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