First time valve adjustment. Need advice - PeachParts Mercedes-Benz Forum

muleears · #1 12-27-2009, 03:47 PM

Trying to adjust the valves on my sons 123. Problem I'm having is, I can turn the adjustment and lock nuts till I'm blue in the face and no change in clearance. I'm ASSuming that the valve is turning with the adjustment nut? How do I prevent this? I have two valve adjusting wrenches but not the third (that I'm guessing holds the valve still). If it isn't the valve turning what else could I be doing wrong? I checked the clearance on the first valve and it was very very tight. Just got the car and don't know when the valves were done last. How many turns of the nut are we talking for an average adjustment? 1/2 turn? 2 turns? 5 turns?

Any insight is appreciated.

rhodes2010 · #2 12-27-2009, 04:10 PM

From your description I would also agree that the valve is turning.

You should easily be able to see it spin.

If you do not have the exact size open end to fit on the valve
get a channel lock or some adjustable wrench and have someone hold the valve
while you break loose the nut and lock nut.

It takes very, very little turning of the adjusting nut to create loose to tight
gaps between the lobe and adjusting nut.

Once the valve and lock nut/adjust nut are loosened you should never have trouble
again.
Once I got my too tight valves loose now adjustments are quite easy.

charmalu · #3 12-27-2009, 10:59 PM

Quote:

Originally Posted by rhodes2010

From your description I would also agree that the valve is turning.

You should easily be able to see it spin.

If you do not have the exact size open end to fit on the valve
get a channel lock or some adjustable wrench and have someone hold the valve
while you break loose the nut and lock nut.

It takes very, very little turning of the adjusting nut to create loose to tight
gaps between the lobe and adjusting nut.

Once the valve and lock nut/adjust nut are loosened you should never have trouble
again.
Once I got my too tight valves loose now adjustments are quite easy.

Did you try the channel locks? maybe with a sexy attendant holding your tool.

Charlie

i-osprey · #4 12-27-2009, 11:52 PM

Are you sure that you have the cam lobe pointing to about 1 o'clock or whatever DG recommends?

It's been a while since I had my W123 but I think the cam lobe should be pointing to 1 o'clock.

muleears · #5 12-28-2009, 03:44 AM

Yes, the cam lobe has been at 1:00pm as DG reccommends. Haven't tried the sexy assistant, she hasn't been available when I was swinging my tool!

oldsinner111 · #6 12-27-2009, 04:11 PM

I can't explain it.As the valves wear the valve seat wears.The valve is moving up to the cam.So you are moving the valve down away from cam.So you hold top nut and lossen bottom nut away from cam.Fine tuning is done with adjustment nut (top).However you need to make sure you have enough threads to adjust.It could be possible that the top nut had no room to turn down away from cam.

jkubica · #7 12-27-2009, 04:12 PM

Quote:

Originally Posted by muleears

Trying to adjust the valves on my sons 123. Problem I'm having is, I can turn the adjustment and lock nuts till I'm blue in the face and no change in clearance. I'm ASSuming that the valve is turning with the adjustment nut? How do I prevent this? I have two valve adjusting wrenches but not the third (that I'm guessing holds the valve still). If it isn't the valve turning what else could I be doing wrong? I checked the clearance on the first valve and it was very very tight. Just got the car and don't know when the valves were done last. How many turns of the nut are we talking for an average adjustment? 1/2 turn? 2 turns? 5 turns?

Any insight is appreciated.

Hi
www.dieselgiant.com has a nice DIY pictorial on valve adjustment. Are you holding one nut steady while you move the other? A number of other tools can be used to hold the valve from rotating but most folks don't find that a problem.
Good Luck,
Joseph

rooster6224 · #8 12-27-2009, 05:58 PM

There are the special valve adj wrenches and additional special tool that you need sometimes. I have found that I only need the additional wrench 1 out 5 valve adjustments.

patbob · #9 12-27-2009, 06:49 PM

Just make sure to measure the clearances after you've fully tightened the two nuts back together again. They'll shift a bit as you tighten them together, possibly enough to throw the clearance off.

muleears · #10 12-27-2009, 07:12 PM

I have a pair of Hazet valve adj. wrenches so I know I have the right size. I have no problem getting the nuts loose. I can loosen the bottom one 1 turn or so then bring the top nut down to meet it and I still have no change in clearance. I still don't understand how I keep the valve from turning. Do I hold the retainer on top of the spring or stick something through the spring? I can get the wrenches on both nuts at the same time, but where do I put another to hold the valve still?

I followed Dieselgiants tutorial, but he doesn't mention how to hold a spinning valve.

tangofox007 · #11 12-27-2009, 07:19 PM

Quote:

Originally Posted by muleears

I still don't understand how I keep the valve from turning. Do I hold the retainer on top of the spring or stick something through the spring?

The retainer is indexed to the valve stem. Immobilizing the retainer prevents valve rotation. Jamming a large, flat screwdriver alongside the retainer is a common strategy.

layback40 · #12 12-28-2009, 06:03 AM

muleears,
when I got my 84 300d I had to back off some of the valve nuts more than 1 turn. Its best to set them on the loose side of the correct gap. They are good at closing the gap them self over time. If they are way too tight before you adjusted them (no gap), chances are if you set the gap correct, they will close up a little in the first few 100 miles.

muleears · #13 12-28-2009, 06:07 AM

Quote:

Originally Posted by layback40

muleears,
when I got my 84 300d I had to back off some of the valve nuts more than 1 turn. Its best to set them on the loose side of the correct gap. They are good at closing the gap them self over time. If they are way too tight before you adjusted them (no gap), chances are if you set the gap correct, they will close up a little in the first few 100 miles.

Thanks Layback, thats good to know.

I will try again today after work using the "wedge the screwdriver" method.

micalk · #14 12-28-2009, 09:02 AM

Don't know if anybody answered this question...

Yes, your valves could be so tight that it takes several turns to set the gap properly. I bought an 82 300sd that hadn't had a valve adjustment for 40,000 miles. Several valve required severe adjustments.

muleears · #15 12-28-2009, 09:19 AM

Am I in danger of dropping the valve into the cylinder if I over adjust? How would I know if I am getting close. I guess there would be excessive clearance?