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

PackerEdgerton · #1 05-10-2015, 02:52 AM

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

PackerEdgerton · #2 05-10-2015, 02:54 AM

I am very very close to just coughing up money to have someone better and more-experienced than I do to the valves (at least this time around). I am at a loss as to what I am doing wrong. Ack.

Packman

Stretch · #3 05-10-2015, 06:06 AM

It sounds like the threads are stripped.

Remove the glow plugs (if you haven't already done so - so you can crank the engine over by hand with ease)

Remove the rocker arm pair associated with the offending valve

Remove the follower and lock nuts and hope that the threads on the valve are not stripped.

Usually the threads in the nuts die first because they are cut whilst the threads on the valves are (probably) rolled (and are therefore stronger)

vstech · #4 05-10-2015, 08:24 AM

If you hold the spring and only turn the locknut, does the top nut spin?

leathermang · #5 05-10-2015, 09:02 AM

I think the answer has already been posted.... hope it is the nuts compared to the end of the valve...
for other people's reference.....
The MB FSM specifically FORBIDS using the Power Steering Nut to rotate the engine because that PS pump shaft is Tapered.... threads in the archive describe the problems over torquing can cause.... and turning the engine over is by definition too much torque.

vstech · #6 05-10-2015, 09:30 AM

Ok, all is not lost.

Try this...

Hold spring, clockwise turn lower nut until it has a good three threads clearance to the top nut. Visually verify the spacing.

Then spin the top nut to meet it.
You could simply have a massively out of adjustment valve.

Graham · #7 05-10-2015, 10:12 AM

Quote:

Originally Posted by leathermang

The MB FSM specifically FORBIDS using the Power Steering Nut to rotate the engine because that PS pump shaft is Tapered.... threads in the archive describe the problems over torquing can cause.... and turning the engine over is by definition too much torque.

What exact section of FSM says that? I recall reading same statement before, but never could find anything in on-line manual. I would like to read where it specifically says that PS nut should not be used as well as what the torque for the nut should be.

The section on valve adjustment says:

I found a section in my paper 107 manual that says torque for the PS pulley nut should be 50Nm (~37ft.lb). Wonder what torque it takes to rotate engine against compression? (I would check, but no clearance for torque wrench)

I am interested, because I usually jog engine to somewhere near proper position, but use PS nut to position more accurately. Taking glow plugs out on a 300D just for valve adjustment, is not an option (for me!)

Stretch · #8 05-10-2015, 10:16 AM

Quote:

Originally Posted by Graham

... Taking glow plugs out on a 300D just for valve adjustment, is not an option (for me!)

Why?

(I'm interested - not argumentative!)

Graham · #9 05-10-2015, 10:22 AM

Quote:

Originally Posted by Stretch

Why?

(I'm interested - not argumentative!)

On the 5cyl 300D, there is a maze of tubing in front of the glow plugs. Getting them out is not easy. At least for me! I have done it once.

Pulling plugs on my 107 is a lot easier, but even there, I use the PS nut to rotate engine.

I hope I am not being argumentative in my previous post. I really would like to know just where MB says not to use the PS nut. I am sure I am not alone in following DieselGiants' great write up on valve adjustment in which he said:

Stretch · #10 05-10-2015, 10:25 AM

Quote:

Originally Posted by Graham

On the 5cyl 300D, there is a maze of tubing in front of the glow plugs. Getting them out is not easy. At least for me! I have done it once.

Pulling plugs on my 107 is a lot easier, but even there, I use the PS nut to rotate engine.

Fair enough - my non turbo doesn't give any trouble - perhaps if you leave them hanging there in the holes? You just need to kill compression (to make turning the crank a whole lot easier)

leathermang · #11 05-10-2015, 10:30 AM

Quote:

Originally Posted by Graham

What exact section of FSM says that? I recall reading same statement before, but never could find anything in on-line manual. I would like to read where it specifically says that PS nut should not be used as well as what the torque for the nut should be.

The section on valve adjustment says:

I found a section in my paper 107 manual that says torque for the PS pulley nut should be 50ft.lb. Wonder what torque it takes to rotate engine against compression? (I would check, but no clearance for torque wrench)

I am interested, because I usually jog engine to somewhere near proper position, but use PS nut to position more accurately. Taking glow plugs out on a 300D just for valve adjustment, is not an option (for me!)

Ok , you caught me.... I JUST MADE IT UP......
lol
it would not surprise me that finding it in the online manual might be hard..or impossible.... I never use the online manual.... I have most every paper manual I know of for my 123 and have sat down and read them front to back... they are not particularly organized... seems like repetition ...where they changed parts or instructions... and the pictures are sketchy many times....
Having been a mechanic for close to fifty years.... I suggest , if it really says 50 lbs for that nut... that that is a TYPO..... perhaps it says 50 INCH lbs.. or some metric something which will convert to way less than 50 ft lbs...
Let me know after you check on the specifics again...

I do find it interesting that people JUMP RIGHT OVER the manual giving specific directions for what TO DO... use the crank nut....why is that ... which you did find.. .not sufficient to convince you that is the correct method to turn the engine...? Some kind of conspiracy theory that they are just trying to make your life or working on your engine Harder ? LOL
Regards, Greg

ALSO .... as a different approach to why one would want to avoid ' interference fit ' on this tapered shaft and its pulley........ if you search the archives you can see my posts about me helping TCane take that pulley off his PS pump ... on a car new to him....
The reason not to use the CAM nut... is that the ' in tension ' side of the engine is the drivers side... using the cam to move the chain....as compared to the chain causing the movement of the cam... means you are ' pushing a chain' ... and you risk introducing a skipped tooth on things like the IP....

Graham · #12 05-10-2015, 10:36 AM

Quote:

Originally Posted by Stretch

Fair enough - my non turbo doesn't give any trouble - perhaps if you leave them hanging there in the holes? You just need to kill compression (to make turning the crank a whole lot easier)

You are right, in that I could probably just slacken them off with the right tools.

But DG's method has worked in past for me. It would be interesting to know what torque is needed on the PS nut to rotate the engine.

leathermang · #13 05-10-2015, 10:47 AM

Quote:

Originally Posted by Graham

......
But DG's method has worked in past for me. It would be interesting to know what torque is needed on the PS nut to rotate the engine.

You have been here since 2004 but trust DG ? Do you not remember him, as a seller of Duracool, promoting that with all sorts of misleading posts ?

to trust him where the FSM says specifically something different......

It is your car....

but a forum is for others to see the discussions and potentially learn from them.... If you mess up your PS pump shaft following his instructions... do you think he will reimburse you for any losses you incur ?

Graham · #14 05-10-2015, 11:02 AM

Quote:

Originally Posted by leathermang

Let me know after you check on the specifics again...

I was not correct and have corrected my post above. The manual says in section 46-710 that torque for that nut is 50 N m which converts to 36.878107449999995 ft/lb.

. Any idea what torque it takes to rotate engine against compression?

leathermang · #15 05-10-2015, 11:15 AM

Graham, Thanks for correcting that....
I do not know what it takes for a diesel Mercedes...
in the past I think for a check of rebuilt American engines I once read that they should take about 50 to 75 lbs to rotate.... without spark plugs in them.... it was a test to see if things like new crank and rod bearings were properly measured and installed....
it was much better to find out on an engine stand that something was too tight.. than to get it into the car with everything bolted up and find the starter would not turn it over... yikes.....
but that would not apply to a diesel engine where the compression was not released... but might be in the ballpark IF the glowplugs had been taken out...