I have an 82 300sd with about 300,000 miles on the engine.

I've had it for over 10 years.
It was a real oil burner.
About 1 qt per 100 miles and hard starting at any temp under about 55° F.

Since I had acquired another MBZ (85 300D), I decided to pull apart the engine on the 82 and have a look inside.
Before I go any further, I want to let you know that I am an Ex-Pat who lives in Mexico and have no easy access to Mercedes parts and also have more time than money.

I usually get my parts when someone comes to visit from the USA.
I order them online and have them shipped to them and they bring the parts here.
So maybe once every 6 months I can get some parts.

To make a long story short.

I replaced 1 piston with a used piston from ebay, all 5 sets of rings new and gaskets and valve guide seals.
I honed the cylinders and placed a ring in it to measure the ring gap and the gap was twice the amount of the upper limits of specs. (at this point I can already hear comments about how I needed to replace the cylinder liners).

I did all this work with the block in the car.
To replace the liners, I would have had to remove the block and completely disassemble it and trust a small time machine shop here to install and bore the cylinder liners correctly.

It would probably end up worse than it was before and with a major expense besides.

I installed the used #1 piston because the original had a broken ring land.
All the rings were stuck in the ring grooves so they required extensive cleanup which I did by hand.
I also took removed all the valves from the cyl head and cleaned them up and did an old fashioned LAP and tested them with solvent.
I also installed new valve seals.
The turbo was all gummed up from the excessive oil consumption.
If I spun the rotor with my finger it would instantly stop.
I took it apart and cleaned it up and got it spinning freely.
I got it all put together and it was hard starting still but when I did get it running, it ran sweet.

No smoke, good power, smooth idle but basically impossible to start without zapping it with 24V.
A cold compression showed about 260 psi and by adding oil it would rise to 310 psi.
So now I figured that I had wasted my time by not changing the cylinder liners while I had it apart.
So I left the car parked for over a year and forgot about it.

Well about a month ago I decided to take another look.
I checked the compression again with my cheap Harbor Freight gauge and it was the same (low) but I discovered that the cheap hose was leaking so I couldn't trust the gauge.
I checked the valve timing and it was late so I fabricated an offset key and brought the cam timing back near specs (maybe even a little advanced, I don't have a dial gauge).
I took the injectors to a place here to test them and also took another set which I had bought years ago from pick a part.
The 5 original injectors were shooting streams of fuel and the PAP injectors were like new, a beautiful spray mist.
I installed the PAP injectors and bled the lines.

I hooked up the battery charger and my heart started beating with anticipation because this was the moment I was waiting for LOL.
1 glow cycle and the car started instantly.
It was about 60° outside.

That night the temp dropped to 38° and in the morning about 6am it was 40°.
I couldn't sleep thinking about whether the engine would start at that temp so I got up and went outside to see LOL.
BTW my wife thought I was crazy.
Again 1 glow cycle and it started instantly, like a brand new engine.

I've been driving it daily for a month now.
No smoke, instant start, smooth idle.
Now that it's running well, I will change the timing chain as soon as I get a visit from the USA Before anyone starts talking about longevity, let me explain that I live in a small town and rarely drive over 45mph and probably less than 1000 miles per year. So if it lasts 20,000 miles, I'll be 75 years old when it dies.

I've been driving only Mercedes diesels since 1985.
I worked as a mechanic at a SF Bay Area Mercedes dealership from 1984-1986.
I love the W123s and the W126s.
My brother thinks I'm nuts!
He drives an 03 C230 Kompressor.

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