Can poorly adjusted valves cause nailing?

[Shern]

Since I’ve owned my 240d, the valves have been adjusted thrice -all hot adjustments because I did not do them myself. I’m preparing to set my IP timing. To be thorough I wanted to confirm the adjustment on a cold engine.
A few valves were a little tight, I did the procedure, triple checked my clearances, and buttoned everything up again.

When I fired her up, nailing.
Not rough running, no rough idle, just nailing. Discouraged, I tried my adjustment again the next day. Still nailing. Loudly on startup, once the engine is at operation temp, only slightly. I loosened my hardlines one by one and isolated the nailing to cylinder one.

After driving the nailing quiets down, as soon as I shut the engine off however (hot engine) and say, run into the post office, for the first 45 seconds of running it nails like it does when it’s a cold engine.

Nailing disappears with even a slight amount of throttle.

I’ve a long drive ahead of me tomorrow and would love to get this sorted before I depart! Help please!

[Diesel911]

Remover the Injector on #1 and #4 Injectors and swap/interchange them and test again. If the nailing now shows up on #4 you have an issue with the Injector.

You don't need a new heat shields during the interchange just to test them.

Note when I first got my Volvo Diesel (uses the same Injectors but different pop pressure) I removed and rebuilt the Injectors with new Nozzles I did not know the heat shields were supposed to be changed. I drove for several on the old heat shields with no issues till I finally read it some where that they were supposed to be changed.

So assuming you heat shields are in correctly I am not seeing an emergency to replace them during the Injector swap or testing.
Replace the heat shield when you have a chance of feel like it.The old 220D engines used reusable plates similar to the heat shields.Of course if your heat shields are at all burned they need replacing.
Note that my way of dealing with the heat shields was to buy like 25 of them back in 2008 when they were around $1 on an internet site. each. They are expensive if you buy them locally.If you prefer the heat shields with the 5mm holes get heat shields for an 1980's VW Rabbit. Seems like the ones they sell for Mercedes now have 10mm holes in them. My Mercedes came with the 5mm holed ones as does my Volvo Diesel

[Diesel911]

If it turns out you are still nailing on #1 check the compression and re-check the valve adjustment on #1.
This link is from my notes however I did not take a look so I am not entirely sure what is in the Link.More Nailing List of causes---http://www.peachparts.com/shopforum/showthread.php?p=2304480#post2304480

[Shern]

Originally Posted by Diesel911

If it turns out you are still nailing on #1 check the compression and re-check the valve adjustment on #1.
This link is from my notes however I did not take a look so I am not entirely sure what is in the Link.More Nailing List of causeshttp://www.peachparts.com/shopforum/showthread.php?p=2304480#post2304480

Yep, I’ve ordered a couple heatshields with just that in mind.
Just to confirm, by silencing the nailing via loosening the injector line, I am eliminating a crappy valve job? It was my first valve adjustment so I’m not totally willing to take myself off the hook.

One thing I found a little odd (found zero instances of this in the archives) is the clearance changed very slightly as the valve rotated. If I set clearance, snugged up the nuts and then rotated the valve spring cap (?) I could feel it changing clearance slightly. As a notorious overthinker, my instinct is to go back in and set clearances again on the tightest spot of rotation. But sounds crazy. And it certainly does nothing to explain the perfect adjustments I’ve had in the past by others more experienced than myself.

[jake12tech]

Valve adjustments are supposed to be done on a stone cold motor. Whoever did them isn’t very smart to do them on a hot engine...

[Shern]

Originally Posted by jake12tech

Valve adjustments are supposed to be done on a stone cold motor. Whoever did them isn’t very smart to do them on a hot engine...

Not to start another one of these debates, but there are hot clearances printed right there under the hood. It can be done if you’re quick.
I am not quick.

[vwnate1]

"Just to confirm, by silencing the nailing via loosening the injector line, I am eliminating a crappy valve job? " (adjustment) .

No, it's just the first step in detecting where the problem possibly lies .

Just do this (swap the injectors) and see what happens ~ if the nailing follows the injector to a different cylinder, this tells you that particular injector is kaput .

If one is bad it's wise to test them all, out of the car .

FWIW : although it's best to only adjust them cold, Ma Mercedes was aware that hot adjustments would be done by necessity, that's why the original valve clearance sticker gave both hot and cold values .

[Shern]

Originally Posted by vwnate1

"Just to confirm, by silencing the nailing via loosening the injector line, I am eliminating a crappy valve job? " (adjustment) .

No, it's just the first step in detecting where the problem possibly lies .

Just do this (swap the injectors) and see what happens ~ if the nailing follows the injector to a different cylinder, this tells you that particular injector is kaput .

If one is bad it's wise to test them all, out of the car .

FWIW : although it's best to only adjust them cold, Ma Mercedes was aware that hot adjustments would be done by necessity, that's why the original valve clearance sticker gave both hot and cold values .

That I shall.

I had these rebuilt only a year ago… I suppose that would be the best case scenario though.

[vwnate1]

It's just trouble shooting, you have to check and re check else you wind up chasing your tail .

All it takes is _one_ bad tank of fuel to screw things up badly .

It may not be any problem at all, don't panic .

I don't quite understand why but the #1 cylinder on OM616's always seem to have more problems ~ bad rods, bad valves, so on and so forth .

Just make sure every thing's right and go on to drive it for a long, inexpen$ive time .

[Sugar Bear]

In a "perfect world", the clearance shouldn't change by rotating the valve. It could be something (carbon) on the valve face and/or seat, an adjustment cap nut slightly off or a slightly bent valve stem. If the compression is good on that cylinder, have zero concern over it.

Yes, I would adjust that valve in the tightest rotation position of the valve so that it gets slightly looser as the valve turns.

Picking up on that was a good observation, attention to detail...

FWIW, I'd have the camshaft/valve timing spot on before adjusting pump timing.

Good luck!!!

[Shern]

Originally Posted by Sugar Bear

In a "perfect world", the clearance shouldn't change by rotating the valve. It could be something (carbon) on the valve face and/or seat, an adjustment cap nut slightly off or a slightly bent valve stem. If the compression is good on that cylinder, have zero concern over it.

Yes, I would adjust that valve in the tightest rotation position of the valve so that it gets slightly looser as the valve turns.

Picking up on that was a good observation, attention to detail...

FWIW, I'd have the camshaft/valve timing spot on before adjusting pump timing.

Good luck!!!

Thank you. And yes, that was precisely my intention...
So, the cover comes off again. When I get to where I’m going I’ll swap injectors and take it from there.

[rocky raccoon]

True "nailing", not a valve tap, is usually an air leak problem. By all means, check your settings again but I expect you will still have the nailing. Look for leaking fuel which will be accompanied by an air leak.

If in the course of your adjustment, you have opened the fuel system by removing the hard fuel lines or changing fuel filters, you will have introduced air into the system. You can bleed the air by any number of methods but I think the OM616, like my OM617 is self-bleeding. Over the next couple of hours of driving, your clatter should lessen and go away.

[Diesel911]

I have this in my notes but don't even know what forum it came from and I don't recall a member The10851Man:
"Valve Adjustment with Valve Rotator in the correct place
In the comments section, posted by The10851Man:
"Wanted to share this with all of you regarding the correct way to adjust the 617 valves. When adjusting, rotate the valve spring retainer. As it rotates, you will notice the clearance will change. Adjust at the TIGHTEST point. This is the #1 reason why 617's run like crap after most shops adjust the valves. Most techs just set the valves and when the valve rotates (as they do normally during operation) the clearances closes up. There is a certain amount of unavoidable runout in the valve train, even on brand new motors. By rotating the retainer (valve and retainer rotate together) you can find the "wide spot" and the "tight spot" in your valve clearance. "Doktor Bert hasn't posted here in a bit."
If your valve guides or rocker arm bushings areas are worn out it also becomes difficult for you to maintain a valve adjustment setting (that includes engines with push rods). I don't know if worn Camshaft bearing areas would do the same but I am guessing yes.

[Diesel911]

I know why I adjust the valves cold. It takes me too much time to do it and you don't know if you are going to get pulled away from the job. When the Engine is cold the temp is extremely stable.

When the Engine is hot and you take a long time to do the job the temp changes faster.

That means I do what is easiest and surest for my own situation. Also a hot engine can be uncomfortable if you put your hands in the wrong place.

If you lived someplace where it is extremely like the Sahara hot it could be would be a good idea to adjust hot. Or just adjust cold and wait till it is the hottest part of the and after longish drive pull the valve cover off and check what the hot clearance is.

[vwnate1]

Interesting .

Is there a specific position to look for or just use the feeler gauge to find the loosest spot ? .

TIA,