One valve refuses to adjust - Om617 - PeachParts Mercedes-Benz Forum

1975300D · #1 11-12-2013, 03:19 PM

Well, I just finished my first ever valve adjustment on my OM617.910.

Everything went well except for one valve. And this one has me worried. One valve, the #3 intake, won't adjust. Both nuts move fine independently, up and down, but no matter what I do, no gap opens up for the feeler gauge. It won't even take a 0.0015 feeler. Nothing.

I can't figure out why this valve won't adjust.

Thoughts appreciated.

75 300D

Stretch · #2 11-12-2013, 03:29 PM

Are you sure the valve isn't spinning round?

The real valve wrench set has two bent 14mm spanners and a third spanner to hold the valve spring cap to stop the valve from spinning

1975300D · #3 11-12-2013, 03:31 PM

Thanks. I was able to adjust all the other ones with the spring spinning. Is the spring not supposed to spin?

Stretch · #4 11-12-2013, 04:17 PM

Well not really it makes the process a bit more difficult if the spring is turning as well.

Pictures of a set of the valve adjusting spanners are in this thread =>

Vlave Wrenches 617 sold on Ebay appear to be new Manufacture not welded.

TnBob · #5 11-12-2013, 06:11 PM

or... as in my D, your nuts could have stripped all the threads and no adjustment is possible. 1st clue to the issue was that cyl had the lowest by far of compression when tested.

1975300D · #6 11-12-2013, 07:39 PM

Thanks Stretch, I clamped the spring. But then I found it impossible to move the nuts. So I gave up on that and released the clamp. But then I noticed I was able to get some clearance. Did that do something? After about 20 minutes of fooling with it, I got it adjusted. For some reason, this one is funny. I hope it isn't some stripping issue like Bob mentioned.

Sorry to hear about your woes Bob. Is there a way of fixing that?

Stretch · #7 11-13-2013, 03:40 AM

Quote:

Originally Posted by 1975300D

Thanks Stretch, I clamped the spring. But then I found it impossible to move the nuts. So I gave up on that and released the clamp. But then I noticed I was able to get some clearance. Did that do something? After about 20 minutes of fooling with it, I got it adjusted. For some reason, this one is funny. I hope it isn't some stripping issue like Bob mentioned.

Sorry to hear about your woes Bob. Is there a way of fixing that?

The only way to fix a stripped thread on a valve stem is to replace the valve (well you might try re-cutting the thread but good luck with that) - so off with its head!

I don't see how you got it adjusted with the lock nuts stuck together.

You could have turned the valve round to a spot where clearance between follower and cam was more apparent. This would indicate that the valve and valve seat is unevenly worn which in turn might indicate a worn valve stem (bit in the head in which the valve slides).

This could be the case but as you are new to this valve adjusting malarkey I recommend that you get your head right on in there and try and look through the clearance gap between the follower and the cam. You'll probably see an uneven thin slit of light rather than a perfectly parallel one - this will give you an idea on where you might want to stick your feeler gauge and where not!

meltedpanda · #8 11-13-2013, 01:59 PM

yup not real sure how you adjusted without moving the nuts. Stretch is probably onto a good idea, however what were you using to move the nuts, they can get VERY tight and take a bit of persuation ?

TnBob · #9 11-13-2013, 07:04 PM

The valve steel is harder than the nut steel. The nuts will strip if over reefed on.

Solution ?? Pop the cam and after clamping the valve replace the nuts

1975300D · #10 11-14-2013, 01:33 AM

I was able to move the nuts after I released the clamp. But before I tried the clamp idea suggested by Stretch, I couldn't make any progress. I don't know how everything interacts behind the scenes. It's weird because I was able to lower the bottom nuts, which compresses the spring, and then I saw the space between the two nuts open up. Then I was able to lower the top nut to take up that space. BUT, and this is the weird part, after I lower the top nut down, the spring is now up again, just as if the bottom nut was never moved!

The whole valve adjustment thing is still a mystery to me, even though I was able to adjust all ten.

Stretch · #11 11-14-2013, 01:57 AM

Quote:

Originally Posted by 1975300D

... BUT, and this is the weird part, after I lower the top nut down, the spring is now up again, just as if the bottom nut was never moved!

The whole valve adjustment thing is still a mystery to me, even though I was able to adjust all ten.

It is easy to get the wrong impression when doing this job - you think you've held that bit tight and done up the other...

...you always need to check the clearance again after tightening.

1975300D · #12 11-14-2013, 07:12 AM

Quote:

t is easy to get the wrong impression when doing this job - you think you've held that bit tight and done up the other...

I must have done this 15 times on that one valve. Each time the same result. I then experimented with another valve, and the same phenomena happens. The bottom nut goes down, the top nut follows it, and yet the spring is back up to where it was to start. Yet, all the valves but one got adjusted without any problem.