85 300cd valve adjustment... - PeachParts Mercedes-Benz Forum

ngarover · #1 03-13-2011, 09:00 PM

Ok, so I attempted my first ever valve adjustment today. I say attempted cause I'm sure I f'd it all up.

Here's the issue. The car idles really rough. I have no ideal when the last adjustment was done, if ever. At spped (70+) car almost feels like it's starving for fuel.

I don't have access to a W123 manual. Could not find any definitive guides searching here and google... There are plenty of threads about setting the Intake to 10mm and the to Exhaust .35mm. No thread or pictorials on how to actually turn the screws, etc. Not really sure that I had the lobes in the correct position. (I had each a little off 12 noon... tried to line them up with that tab on the valve that to me at least looked to be a marker...

If anyone knows of a good step by step, please share. I literally looked for almost 2 hours.

4 of the adjustments, you could not even get the feeler under...

Found it really hard to actually do the adjustment and hold the feeler at the same time... need 3 hands. I have the correct set of wrenches to do it etc.

But got it back together and it started, still shaking but somewhat better. I'll try and get some video of it later and see if anyone came help me diagnose this...

vstech · #2 03-13-2011, 09:09 PM

the first one can be daunting.
also, if the valves were all tight, carbon may be stuck on the valve face.
I'd open it back up and readjust them.
are you working from a drawing of the valve orientation? dieselgiant's page has a good one to download.
are you adjusting from the IP side, or the Manifold side? I think it's best to loosen the adjuster from the IP side, then use the feelers on the manifold side.

ngarover · #3 03-13-2011, 09:18 PM

Quote:

Originally Posted by vstech

the first one can be daunting.
also, if the valves were all tight, carbon may be stuck on the valve face.
I'd open it back up and readjust them.
are you working from a drawing of the valve orientation? dieselgiant's page has a good one to download.
are you adjusting from the IP side, or the Manifold side? I think it's best to loosen the adjuster from the IP side, then use the feelers on the manifold side.

I was doing the feeler on the manifold side, doing the adjustment on the IP side... which makes it about impossible to actually do the adjustment while using the feeler at the same time by yourself. There has to be a trick to it that I'm just not seeing.

vstech · #4 03-13-2011, 09:23 PM

I loosen the lock nut (the lower thin nut) then spin the adjuster nut until the feeler fits in the space a bit loose. then hold the adjuster nut still, and snug up the locker, then reinsert the feeler, then a thinner blade, and a thicker blade. if the thicker won't fit, I'm good.

ngarover · #5 03-13-2011, 09:51 PM

Quote:

Originally Posted by vstech

I loosen the lock nut (the lower thin nut) then spin the adjuster nut until the feeler fits in the space a bit loose. then hold the adjuster nut still, and snug up the locker, then reinsert the feeler, then a thinner blade, and a thicker blade. if the thicker won't fit, I'm good.

Well, I'll have to do it again...

In this pic,

I already know I did it wrong. I positioned each lobe to be even with that tab of metal you see right in front of the first lobe and to the right...

I know I had seen this guide on how to do this before but for the life of me could not find it.

But good practice, as I'm going to also do the 81 300D.

pwjeep · #6 03-14-2011, 11:17 PM

The picture shown in the post by "ngarover" shows an incorrect position of the camshaft. The narrow (pointer) portion of the cam lobe must be pointing at the metal bar to be correctly positioned for checking the valve clearance with the feeler gauge. You can rotate the entire assembly by: Putting a 27mm socket on the crank shaft and rotating it clockwise with a rachet or a breaker bar; putting a wrench on the power steering pump pulley - if the belts are tight enough - and rotating it clockwise; bumping the starter until the narrow portion of the lobe lines up with the "bar". When done use a paint pen to mark the valve just completed. (As taught by W. Hunter.)

vstech · #7 03-14-2011, 11:52 PM

actually, the exhaust valve in the pic (the closest lobe to the front) is in the correct position for adjustment, but the intake is nearly out of position. both can be measured in this position,but it's difficult on the intake with the lobe pointing at the follower... it's easier with it pointing more upward.
the base circle should be equal all the way around, so really, the only position not suitable for measurement of gap is with the lobe pointing at the follower fulcrum. the lobe needs to be pointing up in some way from it.
some cams are worn, and different gaps could be measured on different sections of the base circle, but these cams need replacement.
it's easy to spot the lobe pointing up. be sure to measure gap on the follower to the cam with the cam pointed away.

charmalu · #8 03-15-2011, 12:14 AM

That picture is from Diesel Giant. I usually have it pointing towards the oil pipe.

Wipe off the oil pipe with some brake cleaner on a rag, then mark the pipe with a felt tip pen. "E' for exhaust and "I" for intake. also takes out the confusion of where you are. when I did them the other day, the injectors were out so made turning the engine easier. I did the intakes first and then the exhaust valves.

I have a 7/8 Gear Wrench I use on the power steering nut to turn the engine.
Be sure to wire up the linkage on the injection pump, before bumping the engine with the starter. It could start on you, and with the valve cover off things get exciting.

Charlie