First time valve adjustment - Can't get nuts to turn - PeachParts Mercedes-Benz Forum

Ceristimo · #1 04-17-2016, 07:28 PM

Hey guys,

This Sunday afternoon I figured it would be a great time for some general tune-up on Betsie.

I planned on doing valve adjustment, diesel purge, fuel filter change and oil change.

So, started with the valve adjustment. I'm following this pictorial:
Mercedes Diesel Valve Adjustment Procedure

Got the valve cover off, and I have the first cam lobe pointing straight up. Is this correct? The pictorial talks about it pointing straight up, but also that it will look like it's in the 1 o'clock position. I have it pointed straight up. Should I turn it a little further so it is just a little over straight up?

Second question:
I made two 14mm wrenches with a bend in it to reach the adjusting nuts. I put one on the upper and one on the lower and try to loosen the lower by pushing counter clockwise on the lower, while holding the upper still.

However, I can't get the frikkin' thing to budge. How tight are these nuts? I've never done a valve adjustment before, but I put the work on hold for now until someone get maybe give me some tips or advise on the cam lobe position and on how tight the lock nut is supposed to be?

dkr · #2 04-17-2016, 07:45 PM

I've had the same experience a few times. It takes a while and seems to be counterintuitive.

I've used the same guide and kept the cam lobe in the 1:00 position.

As for how to get them to budge, you might want to try another valve to make sure you are doing it correctly. I've heard some stories about extremely tight valves from not doing the procedure for a long time, but I would try another valve to see you are doing it right first.

How close are the current clearances to spec? Generally, when this is done on schedule you should only have to adjust valves on one or two cylinders.

Dkr.

Ceristimo · #3 04-17-2016, 08:04 PM

So cam lobe in the 1:00 position? This means it's pointing slightly towards the driver's side, correct?

I have only checked the number 1 exhaust valve at this point, and it's too tight. I bought this car 1.5 years ago, the PO said he had done a valve adjustment on it a few months prior to selling it. But then again, the PO said a lot of things. He did include home-made valve adjustment wrenches with the car, so I'm inclined to believe that he did do a valve adjustment.

I have only driven Betsie about 4000 miles since now (in 1.5 years, she's not a daily driver) because I've been focusing on getting it mechanically sound. With new brakes, engine mount, tranny mount, flex discs, drive shaft and half shafts, oil lines, radiator etc all in order I figured I'd do this last job, then start focusing on the ratty interior for the rest of the summer. The fun part, I guess.

Also, counting from the front of the engine (radiator) to the rear (firewall), I'm looking at

1) Exhaust, Intake, 2)Intake, Exhaust, 3) Exhaust, Intake, 4) Intake, Exhaust, 5) Exhaust, Intake.

Is that correct?

I will attempt to see if I can get the number 1 intake valve adjusted...I'll report back

Rogviler · #4 04-17-2016, 08:20 PM

Most of the camshaft is all the same dimension (except the pointy bit of course), so it actually isn't as critical as making sure it's within a degree of pointing this way or that. You can literally only turn the engine a few times, checking all the valves that aren't being touched by the cam lobe or near to being touched and then turning it again and checking the rest. Several on here have tested this and confirmed that it works. It's what I do as well.

Also, if you're trying it turn the bottom nut counter-clockwise looking down at it, that would be tightening it against the top nut.

-Rog

Ceristimo · #5 04-17-2016, 08:56 PM

Okay, I am not getting confused.

Can someone please tell me if I am doing this right, and if not; tell me what I am doing wrong?

1) Have cam lobe at 1 o'clock position, which means the pointy end is pointing slightly towards drivers side
2) Put feeler gauge in (all of my clearances so far seem to be too loose...)
3) Adjust clearance by holding the top nut and loosening the bottom nut. Which way do I turn the bottom nut to release the lock on the upper? Clockwise (tighten, so the nut goes down I guess?) or counter-clockwise?

I am a little confused...

Rogviler · #6 04-17-2016, 09:10 PM

1) Is right, but what I'm saying is that most of the cam lobe is a perfect circle:

So you don't have to be that precise. Just so any portion of the circular part is touching the valve (i.e. none of the pointed part) you're good.

2) Yes.

3) You would turn the bottom nut clockwise, so the nut goes down. If it goes up it's jamming against the top nut. Adjust the clearance, then without moving the top nut, tighten the bottom nut back up against it.

-Rog

Ceristimo · #7 04-17-2016, 09:21 PM

Thaaaaaaaaanks!

That picture of the cam lobe being mostly circular makes sense now! That is why there is so much conflicting information (point straight up, point 1 o' clock etc..)..It doesn't matter

I will go out and try again...Weirdly, all my valve seems just a tad too loose...part of me kinda just wants to put the valve cover back and check it again next year...Thoughts?....

Ceristimo · #8 04-17-2016, 10:17 PM

OK, checked all valves. Most were within spec, or maybe at tad too loose (can slide the feeler gauge in without any resistance).

The ones that were too tight I adjusted to were I can slight the gauge in with a tiny bit of resistance.

I am finding this valve adjustment to be a pain in the rear and an exercise in pure frustration.

When you undo the lower nut and get the top one adjusted perfectly, I find it almost IMPOSSIBLE to tighten up the lower one without moving the top one at all. An almost imperceptible movement of the top wrench in either director will cause the valve to be much too loose, or too tight. Hitting that sweet spot is much more difficult than I thought.

Maybe my technique is just wrong...

At least I am happy to see that most valves were fine, so that does mean the PO wasn't lying when said that he had adjusted the valves.

As for the ones that are a bit too loose, I found several folks saying that to err on the side of caution it's better to be too loose than too tight, and since I find this valve adjustment quite frustrating I decided not to touch the ones that might be just a tad too loose...

Clemson88 · #9 04-17-2016, 10:26 PM

Wouldn't turning the lower nut counter clockwise be tightening it the assembly? Both are threaded the same. Turning the top nut CCW would move it up toward the top of the valve and loosen the assembly so turning the bottom nut the same direction would move it toward the top of the valve, thus, toward the top nut, thus, tightening the two.

The 1 O'clock position is a safe location but I don't think straight up would harm. I think the FMS really wants to make this a idiot proof activity so this idiot always shoots for the 1 O'clock position.

These are RHT aren't they?

As far as adjusting those valves, you'll get better at it. You kinda have to learn to make allowance for the movement in the top nut. That's why they call it a feeler gauge.

Ceristimo · #10 04-17-2016, 10:43 PM

@Clemson88
Thanks man. All valves are either perfect or a tad too loose right now. Most valves were much too loose, but I supposed that is better than too tight. I'm going to put the valve cover back and continue with a diesel purge etc, although I might put it all off until tomorrow...

Junkman · #11 04-17-2016, 11:19 PM

Search "Marshall Booth diesel purge".

Procedure for adjusting valves on some cars is to put the 1st 2 loves at 11:00 & 1:00. Adjust specific valves counting from the front. Turn the engine so that valves 1 & 2 counting from the back are at 1 & 2:00. Adjust the rest of the valves. This works with in line 4 & 6 cylinder engines. I haven't figured it out for this 5 cylinder. I did confirm that you don't need to be precise in how you point the lobe. Just make sure that the rocker isn't on the cam slope.

Ceristimo · #12 04-18-2016, 01:10 AM

Well, I'm of course a total dumb-ass, so don't take anything I say as fact, but...If it's only important that the round part of the lobe is facing the pad, it seems to me you can adjust half your valves, then rotate once and do the other half...

At least, that's how I did it now that Rogviller was so nice to shine some light on the matter, with pictures and all

I just did a diesel purge as well; we'll see if Betsie will run a little better now. She ran fine when cold, just a little clackety and a little smokey...

She was smoking a bit during the purge as well; I ran two cans of the stuff through the engine and what came out of the return was pitch-black.

Now just to change the fuel filters and prime it again, and I'll do the oil change tomorrow (promise!) and we should be good *fingers crossed*.

Rogviler · #13 04-18-2016, 01:33 AM

Sounds like you got it.

Diesel Purge made mine run great, it totally cleared up the clacking and smoke. Then I did a second one and the clacking came back right after and it's been there since. So go easy on it I guess. If it's like Seafoam on a gas engine then it could clean too well, exposing weak points that were previously sealed with old gunk. Speculation though.

-Rog

vstech · #14 04-18-2016, 01:38 AM

Quote:

Originally Posted by Rogviler

1) Is right, but what I'm saying is that most of the cam lobe is a perfect circle:

So you don't have to be that precise. Just so any portion of the circular part is touching the valve (i.e. none of the pointed part) you're good.

2) Yes.

3) You would turn the bottom nut clockwise, so the nut goes down. If it goes up it's jamming against the top nut. Adjust the clearance, then without moving the top nut, tighten the bottom nut back up against it.

-Rog

This is true, BUT, you still need to rotate the lobes into the vertical position to VERIFY the cam base circle hasn't been damaged. I like to adjust all valves in any off lobe position, hen rotate the motor around and recheck e clearances a second time to:
A, allow any tight valves a bit of seat contact to settle any grit that may be stuck to the valve face. And:
B, recheck the lobe in a different position from the first time to be SURE no damage is worn into the cam base circle...

dkr · #15 04-18-2016, 02:23 AM

Strangely enough I seem to remember going through the same thing once and then twice and even a bit the third valve adjustment. It seems like each time my learning curve got a bit faster. I would imagine after some time you just grab the feeler gauges and the wrenches and quickly do whatever needs to be done.

Dkr.