idle probs, loss of power, valves? - PeachParts Mercedes-Benz Forum

bennylo · #1 04-14-2003, 12:37 AM

Hello friends, how is everyone. Ive owned a 78 240D for 1.5 months. Was running great.
not any more. Lost a little power and if that wasnt enough.
when I stop at a light.....the idle is rough.
enough of my poetry though. I'm thinking the valves need to be adjusted. Ive got the
feeler gauges. I understand that there are special wrenches. But Ive also heard you don't
need them. If I don't need them I don't want them. Basically I'm looking for any advice
on how to go abuot this. i.e. How tight should the be on they feelers?What should I do?
What shouldn't I do? I greatly appreciate any advice. Thank you very much all my fellow
deisle heads Bennylolo from the frisco Bay via VT peace.

#2 04-14-2003, 01:12 AM

I adjusted the valves on my 300sd using two open
end 14mm wrenches. The special wrenches would
probably make the job a little easier and I would
get them if I worked on MBs for a living. I think the
78 is similar to my 82, and the Haynes Manual says
the clearence is .1mm on the intake and .3mm for
exhaust, engine cold. The feeler gauge should
slide with a very slight resistance. This is the hard
part, since you must keep the adjusting nut from
turning once it is in the desired spot as you tighten
the locking nut. I don't have a torque spec for
the locking nut but if it is too loose it can turn
back further when the engine is running and reduce
clearence to the point of the valve hitting the piston.
If you apply excessive force you can strip the threads
on the valvestem. I tightened mine pretty hard,
but can't really say to what torque. The job should
not be hurried. If you are just concerned about
how the car runs you can just make sure there
is some clearence on all your valves, if you have
clearence on all valves I don't think that is your
problem.
Mark T 82' 300SD 280K

BIGRED · #3 04-14-2003, 01:55 AM

It could things other than the valves. What makes you think it is valves?

Could be fuel filters, just needing a good ole blowout of engine gunk.

How do you drive it, easy and conservative? jump on it and let the revs get up there? Add any additives to the fuel?

If it were mine and the valves had not been altered since it was running fine, I would first take it for a run and open it up, the kind of opening it up that causes people behind you to wave looking for the lines in the road.

Next I would change the fuel filters.

Good luck

bennylo · #4 04-14-2003, 11:36 PM

hey this is bennylo. replaced the filters and drove it hard. It runs better but its still not right should I turn up the idle. or try some other things first. let me know.

ned2683 · #5 04-14-2003, 11:40 PM

trying running a can of diesel purge through it.

dieseldaddy · #6 04-15-2003, 07:56 AM

I have the same symptoms on my 81 300TDT...I adjusted the valves, changed both fuel filters, and ran *6* cans of DP thru it! No change. I now also have a rough idle all the time, worse after a hard run.

Here is my humble suggestion, check the rack dampener, and possibly motor mounts. That is what my next task will be...