Rocker arm movement during valve adjustment

Hi!

I've never adjusted the valves on an engine before, so perhaps I'm just being a bit too worrisome. When adjusting the valves on my 300 TDi with about 40,000 miles, I apply a little force to the feeler gauge to force the rocker arm to raise just a bit (less than .20 mm). This lifting appears to seat the adjustment screw into the push rod. This is without loosening the lock nut or adjuster screw, and once lifted the rocker arm stays up on its own. After the rocker arm raises, the feeler gauge fit looks to be correct: .20 mm fits, .25 mm will not. If I just try to slide the feeler gauge in gently with no force on the rocker arm, the feeler gauge will not fit.

If I loosen the lock nut and adjuster screw to adjust the clearance, I have to raise the arm manually anyway upon loosening the screw.

The first time I adjusted the valves, I had to tighten all the valves - I have my doubts as to whether it's ever been adjusted.

So am I worried about nothing? What prompts this post is a serious drop in mileage, from about 25-26 MPG to about 21-22 MPG. Of course, I changed a few other things: connected cyclonic breather to the air inlet rather than open to ground, fixed a coolant leak, changed to synthetic 15w40. Also, the last time I checked mileage the weather was fairly warm, and it's cooled significantly since (but I have kept the engine temperature up). And I still haven't examined the air filter.

Thanks in advance,
Michael

Sounds like you are worrying about nothing if I am reading it right, because by doing the valve clearances you are checking the gap, which would mean there would be a small bit of movement in the rocker arm when the valve is fully closed. As long as it's not side to side it should be fine

Put one finger on the adjuster to take up any slack, then slip the gauge in with the other hand, it should slide in but only just, don't force it, its all done by feel.

If it won't just slide in then the gap is likely too small. Always use the rule of 9 when setting I.e. Valve 1 open so adjust valve 8 etc.

hello

could you tell us what the symptoms would be from poorly adjusted valve clearances??

thanks J.

martyc said:

Sounds like you are worrying about nothing if I am reading it right, because by doing the valve clearances you are checking the gap, which would mean there would be a small bit of movement in the rocker arm when the valve is fully closed. As long as it's not side to side it should be fine

Click to expand...

davek0974 said:

Put one finger on the adjuster to take up any slack, then slip the gauge in with the other hand, it should slide in but only just, don't force it, its all done by feel.

If it won't just slide in then the gap is likely too small. Always use the rule of 9 when setting I.e. Valve 1 open so adjust valve 8 etc.

Click to expand...

Sounds like I did things right then. My air filter is grey on the outside, so that needs replaced. I was adding an Optilube diesel additive, so I'll run a few tanks without to see if that also has an effect. A bit of a cold snap here, so no chance to run it in warm weather until Sunday.

MichaelAllen said:

Sounds like I did things right then. My air filter is grey on the outside, so that needs replaced. I was adding an Optilube diesel additive, so I'll run a few tanks without to see if that also has an effect. A bit of a cold snap here, so no chance to run it in warm weather until Sunday.

Click to expand...

:welcome2:

Air filter should be the first thing to change and change it at least every 3000 miles (twice a year ish) or more often if you can afford it.

Tappets, once set, should be ok for years as long as you change the oil and filter regularly.

In the cold weather your engine should run more economically as long as the engine keeps up to normal temperature. The intake air is cold and damp and that is just as diesels like it.

Keep the revs down and no heavy braking will save fuel as will keeping the speed down.

landowner said:

:welcome2:

Air filter should be the first thing to change and change it at least every 3000 miles (twice a year ish) or more often if you can afford it.

Tappets, once set, should be ok for years as long as you change the oil and filter regularly.

In the cold weather your engine should run more economically as long as the engine keeps up to normal temperature. The intake air is cold and damp and that is just as diesels like it.

Keep the revs down and no heavy braking will save fuel as will keeping the speed down.

Click to expand...

Thanks for the welcome & info. New air filter purchased and installed; the previous owner kept the original 2.5 N/A filter housing, so I'm using the 2.5 N/A air filter.

Oil & oil filter were changed about 3600 miles ago, about a month ago, before a long road trip.

Most of my driving is highway miles - steady @ 65 MPH. I took my mileage measurements on mostly (or almost all in a couple of cases) highway - no stop lights, just occasional soda/toilet stops.

And the air is cool and dry here in Texas, especially in winter (hot & dry in the summer). I've got my sheet of plywood blocking 3/4 of the air flow.

I'm planning on tackling the fuel filter next. Seems like an easy enough job. The previous owner had the fuel tank repaired just before selling it to me; maybe there was crap in the tank that's clogged the filter.

Worth remembering winter diesel has more naptha in it to stop waxing,the energy content of winter diesel is less than summer diesel-so you will see less mpg.In your case changing the air and fuel filter should show some gains

Thanks for the info about diesel - I wasn't aware of that. I wonder if that's true even down south here where the average low temperature in winter is about freezing (30 F).

I changed the fuel cap, too; the old one didn't have a very good fit. I imagine a bit of water crept in during some of the heavy storms I've driven through.

I'll check the mileage again after I tackle a couple of rust issues...