New car project starts on Monday - PeachParts Mercedes-Benz Forum

engatwork · #1 02-11-2010, 07:38 PM

I will be replacing the head gasket and oil pump on my '95 E300 with 254k miles starting over the next few days. If there is anything anyone wants pictures of let me know. Issues are a slight head gasket leak at the passenger side rear of the block and low oil pressure at idle. I may get in there and just rebuild the engine. I can feel a case of "while I'm in there itis" coming on

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konstan · #2 02-11-2010, 07:46 PM

Are you going to lift the head off just using hands or a hoist?

Curios because I am about to pull a head and have not done that before.

And yes I would like to see pics of (1) cylinders and pistons and (2) valves i.e. bottom of the head.

Good luck with your project!!!

CSchmidt · #3 02-11-2010, 09:06 PM

"I can feel a case of "while I'm in there itis" coming on. "

I used to follow a Jag forum and they called it "shipwright's disease". The curse of never ending maintenance to make everything perfect. Good luck!

d.delano · #4 02-11-2010, 11:30 PM

How do you know the oil pump's bad? Low oil pressure can be caused by bad bearings as well, yes? Just a thought- the MB diesel oil pumps are supposed to be very robust.

engatwork · #5 02-12-2010, 06:09 AM

I'll see what kind of clearances I have when I get in there but I suspect there is something going on in the oil pump area.

compress ignite · #6 02-12-2010, 10:06 AM

"After many weeks and a few red herrings, we finally tracked down the
oil pressure issue plaguing my '95 E300D. Checking through MB's tech
bulletins, I thought I had nailed it. On the 606 motors (and
probably others) the camshafts are hollow and oil runs down
them. There is a freeze plug at either end of the
camshaft. According to MB, these freeze plugs can fail and become
dislodged. When this happens, all the oil gets pumped up into the
valve cover and the low oil light comes on, followed by loss of oil
pressure. Since this sounded like my symptoms, we tore down the top
of the motor and pulled the valve cover (a time-intensive job on a
606). Sadly, when the camshafts where checked, it was confirmed that
all freeze plugs were in place and not leaking. The next step was to
check the pan. Instead of dropping the pan, we removed the oil
cooler from the side of the pan (which required draining the oil and
the coolant, since it is an oil to water heat exchanger). Once
removed, the issue quickly became obvious. The screw plug that
retains the oil pressure relief valve to the oil pump had backed out
to the point where only one or two threads kept it from dropping into
the pan. This effectively removed any preload on the oil pressure
relief valve spring and put it into "bypass" mode. Since neither the
oil pump nor the oil pressure relief valve had ever been replaced or
removed on this vehicle, I am at a loss as to how it would have
backed out. It was re-torqued to 50 Nm, the vehicle was reassembled,
and we manually primed the lubrication system through the pressure
sender fitting to make sure all bearings had oil. The engine was
restarted and oil pressure immediately returned."

"Now, I realize that my particular vehicle tends to exhibit problems
that by themselves are unusual and rare and in combination almost
inconceivably unlikely, but if this happened to me it could happen to
someone else. If you happen to have the oil pan off your 606 motor
(other 60x might be similar), you might want to re-torque the oil
pressure relief valve screw plug while you're in there. If you
happen to loose oil pressure, this might be something you want to
check. 18-5031HA in the service manual covers the installation and
removal of the oil pressure relief valve.

Regards,

J.B. Hebert "

[#65 in the Cyrillic Pictogram]

[Which just added a second component to be "Loctite-ed" in my Lubrication System,along with the Bolt securing the Oil Pump Drive Sprocket to the OP.]

engatwork · #7 02-18-2010, 08:16 PM

I received the new oil pressure sending unit today and it is reading 10.5 ohm versus 15 ohms on the old one. I will put the old one in the wife's car this weekend and see if I see the oil pressure drop like I had been seeing on mine. If it is then I've got a bad oil pressure sending unit

and that is a good thing. All I'll have to do is replace the guides and re-install the head.

I've said it before and I'll say it again. If you have over 250k miles on your aluminum head five or six cylinder diesel Mercedes (probably applies to the gassers too) plan on replacing the oil pump chain tensioner between 260k and 300k miles if oil changes have been done properly based on usage. The one in the pic has 254k miles on it and comes out of an engine that has been properly maintained with mostly highway mileage. The timing chain tensioner shows very little wear and could probably run another 200k from what I can tell but it will get changed out.

I do not see any indication on the cam bearings which would be indicative of low oil pressure.

Chris W. · #8 02-19-2010, 12:58 PM

Jim,
Is that oil pump chain tensioner something that can be done without huge surgery on the engine? Or must you have the head off, oil pan off, timing cover off, etc. My '95 has just rolled over 307K, with religiously done oil changes and overall good maintenance.

Rgds,
Chris W.
'95 E300D, 307K

babymog · #9 02-19-2010, 01:30 PM

Religiously done oil changes? Sunday only?

engatwork · #10 02-20-2010, 03:30 PM

The front cover has to come off. I have done the job without pulling the head but it is hard not to mess up the oil pan gasket.

I put the "suspect" oil pressure sending unit in the wifes car and it gave the same low reading at idle

. The work load on the unit just got a lot less thank goodness.