Hello,

I have a '13 SL550 which I'm in the process of replacing the tensioners and installing check valves. I've removed the passenger tensioner and found that there is no check valve in the head, and it appears to be a non-stepped bore (a 5/16 drill bit also does not fit into the bore). I have both check valves, 2780504000 (non-stepped) and 2780503300 (stepped) but am having an issue with fitment.

Given that my head is non-stepped, the 2780504000 should fit but does not. The valve will not even slightly enter the head, and it looks as though I need it to be 80% in for the press tool to work. I've left it in the freezer overnight to try and shrink it some, but that didn't work either. Is there something I'm missing?

You're on the right track...


not going in
You need check-valve that fits in...

> Do it once only!
Observe oil flows through FORWARD.

The factory installed valve is hardly removable ie. not serviceable... the shoulder is passed the threaded section - It comes apart inside!

BTW these ratcheting tensioners already have a built-in internal check-valve.
The extra check-valve helps prioritize startup oil pressure towards the camshafts phasers first.

I have the other stepped valve also, and that fits - but loosely. Given that the bore is non-stepped, this non-stepped valve should fit according to Mercedes. I’m sure I can press the stepped valve into place but I don’t think that’s going to work in the long run.

Is there another variant of this non stepped valve that is smaller?

Only two types are available.

Valve in or not... not a game changer.

The phaser + tensioner rattling is caused by low oil pressure.
I you don't want to wear out your phaser locks, you can experiment disabling low oil pressure that saves up to 1% gas.

Thank you, I have already done the oil solenoid disconnect after studying your thread quite a bit. I’m keen on the check valve as it is the source of my startup rattle, and I am this far already. My car is a late 2012 build and has no check valves and original tensioners. I suppose I just have to figure out how to get this non stepped valve into the head, perhaps with applied heat and another round in the freezer for the valve itself.

I agree, don't back down!
Lets find a way...


> Rattlers oil supply:
-- There is hardly any oil flow through towards tensioner, only static pressure.
-- Phasers do require oil flow through supply.
Meaning if you seriously file your new check valve to avoid damaging your heads, you'll be doing nothing wrong.

> SOLUTION:
Can you ease valve diameter with fine grit 1000 sand-paper ???

File/sand down check-valve so it gets in simply by hand.

It really shouldn't need to be pressed in hard.

Hope this helps you.


Make sure valve goes all the way inside flush so tensioners backside can seal pressure against the head surface without RTV.

Thank you - the sanding option definitely crossed my mind, but was a last resort. It's probably the only bet for this situation.

you don't want to spend 2 days on this for no good reason - The head's integrity is more important than the cheap valves.

The low stress check-valves do not require to be pressed with brute force.... finger tight!

I like the way you have a shop towel in there to catch any contaminants and tools on the way down.


While you got your 1000- grit sand paper handy:
sand the tensioners backside smooth.
The genuine MB tensioners feature a rough machining finish not so great to seal with heads.

Sand using a flat surface like kitchen granite/marble counter.

I don't suppose you know the actual ID and OD so we know how far it's off? My guess is it's just a bit tighter than usual for whatever reason, and needs some force and/or sanding.
If I knew how close the fit was, and consider it acceptable, I'd just grease it and pound it in. Grease makes a big difference. Real grease, not Silicone or Superlube etc.
I'm not much of a special tool kinda guy, so either way I'd pound it in. Plus, if you pound it a bit now it will tell you by feel if it will go in all the way, or is it just too tight and you may not get it all the way in. If I even remotely thought it may not pound all the way in, I'd sand it.

To sand things like that I chuck it into a hand drill, then squeeze sandpaper on the exposed part of the valve. Obviously chuck the forward side into the drill and sand the aft end.
I would not use 1000 grit, you could be there all day. I'd likely use 320, and quality Wet/Dry like 3M. Sanding like that will typically sand the end more giving it a bit of a taper, which is a good thing for test fitting, to tell you how much you need to sand to make it slide in.
If just a little sanding does the trick then I suppose I'd sand so ~75% of it goes in by hand, leaving the remainder to be a press fit in the head for sealing. If you have to remove a lot and it seems like that little remaining press fit part might be too tight, then I'd turn the valve around in the drill and sand a bit off the fwd end until I feel comfortable with the press fit.
Rather than sand by hand, I often use a Dremel. So again the drill acts like a Lathe, but now you're using a sanding disk on a Dremel to sand it down. I suppose I'd use 180 to 220 discs grit for that. A Dremel would be especially handy because you have more control, so you could sand 90-95% of it if you wanted, allowing for a tighter press fit but less of it. The only point of the press fit is that it's an air tight seal. Speaking of, I might even use Loctite on the last 10% to ensure it's air tight. Probably Loctite 569 because it's more of a sealer than a thread locker.

Optionally you could sand the hole in the head instead, but I know very few would consider this. If you're open to it, I can explain how to do it perfectly, and almost free.

As for the tensioners surface, I'd agree with Cali and sand it. It's sealing is not as important as the check valve, but it still helps if it actually seals. It still won't seal air tight but sanding will no doubt help. I usually use a sheet of sandpaper on a sheet of glass, like a glass table, mirror. Again quality wet/dry, and in this case a new sheet. Not sure I'd start with 1000, but I'd likely end with it or finer. If it were me I'd likely use Loctite 569 on it that too, so it would actually seal. It would only need a very very thin coating.

Op got it in with a bit more oomph…