Hello, You giys have been such a great heklp to me in the pas ton all 3 of
my mercedes. My question now is in regards to removing my 89 300e head.
The motor has low compression in 1 of the cylinders and has some tapping
from the valves. The one mechanic told me the head has to come off and is
in the need of new seals, stems, and guides. I guess because its a straight
6, it shouldnt be to bad for the removal process. I was then just gonna
bring the head to a machine shop and have him do the whole 9 to the head.
My question is do I have to worry aboutworry about anything like retiming
the fuel injection system after i get the redone head on? And can the bad
head promote a motor misfiring from a cylinder and rough running? I did
everything else to the motor, plugs, cap, wiress, ect. And do the M103
motors ever have a problem with bad motor rings? I dontthink mine
does.....Thank you all
i should of also said that the car burns no oil whatsoever...... i changed
the oil wil mobile 1 in july and went 2500 miles and there is no oil
consumption. The oil pressure is good too. Shouldnt this mean that the
rings are in good condition and not worn??? The car has about 120K on it.
But the one mechanic the head has to be pulled for valve work....... Is
there any other thing i can do for the motor while the head is off?
It doesn't burn oil. It's done 120K miles. It has low compression in one
Most likely a burned valve. The valve guides and seals seem to be OK as
are the piston rings - unless a compression ring is broken.
Pull off the head; I'm pretty sure you'll find a burned valve in the low
If you've lost compression then you've probably got a head gasket leak, a valve
leak or piston ring leak. You might want to have compression & leakdown tests
run to see which is most likely before you start taking it apart.
Having done that, the head will have to come off, regardless of which of the 3
likely sources is the problem. And as you have the head off, you may as well
have new guides & seals and the head skimmed at your machine shop. (You could
also have new valves & springs if you think these would be worth it)
I have looked into removing the head on my own 92 300e, and it seems fairly
straighforward, with the major gotcha being the cam timing chain. Make sure
you mark it & the sprocket so you know where it goes back, and keep it tight so
it doesn't skip teeth on the crank sprocket. The intake manifold & fuel
distributor remain attached to the head when you remove it from the block, and
are taken off (& replaced) on the bench.
The European Haynes manual (ISBN 1 85960 253 3) seems to cover the procedure
quite well, so you may want to lay your hands on a copy before digging in.
Good luck, let us know how it goes.
i may of forgot to say that on the bad cyclider, the electrode to the spark
plugs have a decent amount of oil on them after a few hundred miles....
Someone else told me that at 120K it would be rare for the rings to be
bad. So to end the question, would bad valves, seals, and overall worn
valve guides make the motor misfire and run like crap at idle and on a
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