Frustration with W123 Valve Adjustment! - Page 4 - PeachParts Mercedes-Benz Forum

whunter · #46 05-11-2015, 04:26 PM

Quote:

Originally Posted by PackerEdgerton

Hi guys,

I am now on my 3rd W123 (they have all been 240Ds with 4 speed manual transmissions).

I have done valve adjustments before. Not a big deal, they just take some time and patience, most of the time... except for today.

I spent 90 minutes trying to adjust ONE valve, and it's driving me crazy.

Here's the situation:

I know it's due for a valve adjust, but this car is relatively new to me, i.e. this is the first valve adjust I've done on this vehicle.
I have all the correct wrenches and tools, including proper offset wrenches and even the spring holder tool (Hazmet)
Popped the valve cover off, used a 22mm socket on the power steering pump pulley nut to crank the engine over so that the cam lobe of exhaust valve for cylinder 1 is 90 degrees from the surface of the rocker.
Feeler gauge won't even fit... it's clearly super tight. I don't think there is any clearance at all.
I put the spring holder wrench on per the FSM
I then use my offset wrench to hold the top nut while loosening the bottom one.
I then hold the bottom nut while turning the top nut clockwise (as seen looking down at the assembly). I turn and check the clearance over and over, but it doesn't ever get big enough to fit the feeler gauge!
In fact, I don't think it's doing much of anything!
I tried using DMorrison's method of tightening both nuts together, and just turning the bottom nut counterclockwise.
I crank the engine all the way over to ensure that the cam lobe is really in the right position.

No matter what I try, I can't seem to get ANY spacing between the cam and the rocker! Ugh! I've never run into this before.

Am I doing something wrong? Any hints?

Thanks,

Packman

Sounds like:

1#. Failed threads on the jam nut?

2#. A valve height issue.

The nut is a PIA, but most people can DIY.

The valve height issue is more complex, possibly requiring cylinder head removal.
If the valve seat and/or face is worn beyond specification = the valve stem will protrude (stick out) to far above the cylinder head deck = no further adjustment is possible.

There are two normal answers for this issue:

Warning, danger, the following procedure is usually performed with the cylinder head removed, in a professional machine shop.
A#. Remove the rocker and valve CAP nut, (drape / protect all internal engine parts from grit), extreme caution: use a die grinder to remove 1.5 MM off the top of the valve stem, EXTREME cleaning is required before reassembly.

B#. Far more common: Remove the cylinder head, and have a professional machine shop service the valve face, seat, guides.

Have a great day.
.

leathermang · #47 05-11-2015, 05:12 PM

The FSM suggests that if one has the valve train down to do something like replace the valve stem seals.... .that the valve cap and lock nut be ' renewed ' in their words....
These items are are subject to trillions of impacts over the years.... it is amazing to me we have so few examples of valve cap and lock nut issues....
The type of cap must be matched to the camshaft in the car.. check cam numbers before replacing.....
Fingers crossed that it is this... compared to valve seat wear... yikes....

PackerEdgerton · #48 05-11-2015, 07:16 PM

Quote:

Originally Posted by Shortsguy1

Yes, I read that in his first post as well, but this statement seems inconsistent to me..."I think that the top nut appears to be 'stuck' on the top of the valve". So I was wondering if perhaps he was using the third wrench incorrectly. I have never had to use one, so I am not passing judgement. I just felt there was an inconsistent statement that should be evaluated before he took the engine further apart.

Hi Shortsguy1,

No worries, I'm always ready to learn something new, and if I am using the tools improperly, I can learn a new way!

The third wrench I am using exactly as seen in the image attached here.

My understanding is that it keeps the valve from turning around and around as you attempt to turn the adjustment nuts.

I agree that the two statements appear inconsistent, I'm just trying to express what I am seeing. I suppose I could do a video... but I'd need an extra hand.

Sincerely,

Packman

Lucas · #49 05-11-2015, 10:38 PM

Third wrench?

Lucas · #50 05-11-2015, 10:47 PM

Quote:

Originally Posted by moon161

After a few tries, I learned not to attend every argument that I have an invite too. On the original topic, it seems to me that the threads on the stem of the valve in question were probably stripped when someone with a couple wrenches over-tightened the the jam nut. That may not actually be the case, but that best explains the phenomenon of a nut that moved in rotation, but not translation.

In you efforts to examine or verify the issue, take appropriate care not to drop the valve down the hole. Recently, I someone (member Lucas?) dropped one and got it back, but it was a nail-biter.

My guess is to do anything besides drive as-is, the head comes off. Once that happens, you open up all the 'while you're in there's' and 'is it worth it's'. Minimally, parts would be new HG and valve, set of bolts at your discretion (another controversial topic).

Nope. I refer to the fsm and you all to avoid those problems. Good thing is, you can set the piston to hold the valve. Unless you really know whats going on, i would pull the prechamber and verify the location with a long thingy. But i dont think you need to remove your bottom nut.

I remember discussing and the topic and some weird trick i saw to get it back up.

The problem is you are so tight that the valve is spinning. Gotta pull the rockers. Thats easy.

I never use a third wrench. I clean the threads. Never spins on me.

Pull the rockers. Bring the top nut up, botton nut down, clean, move nuts around, repeat.

vstech · #51 05-11-2015, 11:42 PM

If the jamnut (the lower nut) is turning, and space is made between the two nuts, the threads on it are good. If turning the top nut takes up the space, the top nut isn't bad.
The third wrench holding the spring from turning shouldn't allow the valve to turn...

You may need to have more turns on the jamnut...

PackerEdgerton · #52 05-11-2015, 11:58 PM

Quote:

Originally Posted by Lucas

Pull the rockers. Bring the top nut up, botton nut down, clean, move nuts around, repeat.

I'm going to try and follow VSTech's advice, but I would like clarification on this statement.

How hard is it to pull the rockers? Do you mean to actually disassemble the rocker arms?

I've never done that, it looks pretty intimidating.

Sincerely,

Packman.

PackerEdgerton · #53 05-12-2015, 12:08 AM

Quote:

Originally Posted by vstech

If the jamnut (the lower nut) is turning, and space is made between the two nuts, the threads on it are good. If turning the top nut takes up the space, the top nut isn't bad.
The third wrench holding the spring from turning shouldn't allow the valve to turn...

You may need to have more turns on the jamnut...

Thanks for reaching out VSTech. OK, do I have this right?

1) 3rd wrench is holding the spring and keeping the valve from turning.
2) Lower jamnut is definitely turning, and I can definitely get a space between the top nut and the jamnut (lower nut, aka lock nut).
3) When I turn the top nut, it definitely turns while the jamnut stays still (even when I don't have a wrench on the jamnut), and the space between the nuts disappears.

So, this would seem to imply that the threads may be OK, and it's just way way way out of adjustment?

Sincerely,

Packman.

vstech · #54 05-12-2015, 01:05 AM

I mac be wrong, it happens...

But my understanding is the valve cannot rotate if the spring nut is held still... I find it nearly impossible to believe there is that much wear in the valve face though.

The valve may be destroyed...

Take pics, and use good lighting and watch the valve stem when turning the top nut. If it's not turning when the top nut is...

PackerEdgerton · #55 05-12-2015, 02:51 AM

OK, I think I figured it out.

The middle nut (the jamnut) is partially stripped. The top nut, however, is OK.

So here's what happens.

1) When you turn the jamnut, it turns, and the top nut stays right where it is. The jam nut also moves down a little bit.

2) When you turn the top nut, it moves down to clamp on the jamnut.

3) I did this over and over and voila, I was finally able to slip the feeler gauge in!

4) I was able to use the top nut to adjust the spacing and get it to be snug, as the FSM indicates.

5) When I tried to use the jamnut to "lock in" the adjustment as the FSM indicates, The jamnut would move up, but it wouldn't clamp firmly to the top nut (well, not as firmly as I would like).

6) The other valves adjusted just fine.

I believe that the #1 exhaust valve was way way out of adjustment, and likely because the jamnut is slightly stripped, allowing the top nut to move a little bit during operation.

I'm worn out from fiddling with it, but that's my observation.

Thank you guys for all your help. You are fabulous!

I think I will need to save up some energy and likely replace both nuts on the #1 exhaust valve. For now, it's within spec and will probably be OK at least for awhile. We'll see.

Thanks again,

Packman

Lucas · #56 05-12-2015, 04:53 AM

Quote:

Originally Posted by PackerEdgerton

I'm going to try and follow VSTech's advice, but I would like clarification on this statement.

How hard is it to pull the rockers? Do you mean to actually disassemble the rocker arms?

I've never done that, it looks pretty intimidating.

Sincerely,

Packman.

Man I got lost in all the nut discussion. But glad it worked out. I would say make sure its tight, or check it soon. If the outside of the nut was already kinda stripped, you can see why that valve got so tight. Even if you have to lock on with vise grips or channel locks (i may get some slack, but robogrips are sweet), and plan to replace it next time.

I missed that part originally.

But the rockers are easy. Mainly because they bolt into the head, not through it.

Just loosen the bolts and remove. They ride in a little collar. Maybe 0.5mm tall. Pretty firm fit

Wiggle wiggle wiggle. Some may say to not use a rubber mallet...

But once off they slip right out. Maybe a struggle if you are tight. I usually drop the valves down some. Kinda cache 22 in your case.

But necessary next time when you replace that nut.

I have a head on my bench. Ill try to shoot a pic. Although my track record with that has been inconsistent.

Stretch · #57 05-12-2015, 08:08 AM

I don't want to bring doom and gloom...

...but...

if

the

nut

doesn't

lock

it

will

come

loose

very

quickly

(Sorry about that)

Maxbumpo · #58 05-12-2015, 10:06 AM

Packman - don't delay making the necessary repair, too much risk of damage (valve meets piston).

PackerEdgerton · #59 05-12-2015, 10:51 AM

Quote:

Originally Posted by Lucas

But the rockers are easy. Mainly because they bolt into the head, not through it.

Just loosen the bolts and remove. They ride in a little collar. Maybe 0.5mm tall. Pretty firm fit

Wiggle wiggle wiggle. Some may say to not use a rubber mallet...

But once off they slip right out. Maybe a struggle if you are tight. I usually drop the valves down some. Kinda cache 22 in your case.

But necessary next time when you replace that nut.

I have a head on my bench. Ill try to shoot a pic. Although my track record with that has been inconsistent.

I would love any guidance or photos here. I admit to being a little scared of this job, having never tackled it before.

Thanks,

Packman

PackerEdgerton · #60 05-12-2015, 10:52 AM

Stretch and Maxbumpo,

Of course you are right, and I need to get on it right away. I guess I'm scared because I haven't done any of this before (e.g. disassemble rockers, repair/replace valve adjustment nuts, risk dropping one, etc.)

Any photos or hints are welcomed.

Thanks,

Packman