I’m contemplating doing a rebuild of the original Garrett T3 turbocharger on my 1985 300D (617.952) with about 220,000 miles. There appears to be an oil leak.

In picture 1 here, there is some oil that has collected at the base of the wastegate diaphragm. I have not been able to determine whether or not the diaphragm has a hole/slit. Picture 2 shows the diaphragm after I wiped the oil out. I didn’t see a hole/slit when inspecting the diaphragm:
1. With the wastegate depressed.
2. Using a magnifying glass.
Questions:
> Is there another way to check whether or not the diaphragm has a hole/slit?
> Could the oil be coming from further inside the turbo and simply leaking past the diaphragm?

As for the condition of the compressor impeller, it looks quite good (no visible nicks or damage) and there is very little play when I try to move it laterally with my fingers.

So:
Where might the oil leak be originating from?
After 220,000 miles and almost 38 years of service, is a rebuild in order?

I’d appreciate feedback about this. Thanks-

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I'd say the oil there is from the engine and it's simply collecting and weeping past the edge .

At this mileage the turbo likely needs a routine overhaul, not difficult at all but before that you need to do a major tune up and boost testing as the waste gate is adjustable, factory was something like 12" I set mine to 16" after overhauling the engine and turbo both .

Don't go crazy over boosting ! it will shorten up the engine's life, it will cause it to run too hot and fry the rings and pistons, allowing it to still run but smoke constantly .

There is a manifold pressure sensing pipe that runs through a safety over boost switch then to the ALDA on top of the injection pump, this is often clogged and needs cleaning along with the banjo bolts at the back of the intake manifold and ALDA plus I often find the safety relay is clogged shut or nearly so .

All this cleaning is dead simple and easy if filthy and you'll be amazed at how much better performance the car has when it's clean and there's at least 12" or boost as the ALDA richens the mixture as the boost goes up .

The shaft in the turbo should be easy to spin by finger with zero drag and no radial (side to side) play at all and minimal foe and aft play .

Kits are cheap at $60 or so, I replaced the impeller shaft because old....

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

What are the other possibilities?

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I dunno .

I've seen these poor overworked cars with oil every where, after a while it can be daunting to know where any particular pool of oil is from .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Thank you, Nate.

Yes! I've been studying the archives here and there is good information about all of this. My banjo bolts at the manifold and ALDA are clean (I checked) but I'd like to go back and check that the tubing allows for easy unobstructed airflow.

As for the safety relay, that I have not checked but will. Unless you or someone else tells me otherwise, I'm assuming that it is a simple matter of applying 12 volts and the valve opens or closes and in the open position, air should flow freely.

The subject of the amount of boost pressure and how to test is discussed in the archives and I'm one for conservative on such matters so I will certainly opt for boost that stays clear of running too hot.

What I don't quite understand yet is what sort of gauge I need and I'll have to go back to the archives to see how to tee off so that I can drive under load on the freeway and have the gauge inside the car so that I can take a reading.

Turns easily, feel no drag, ever so slight play.

This is a curious subject...Last week, I looked into rebuild kits and had unexpected results:
M&D / M&M Distributors – The guy couldn't find Garrett T3 part number 466424 or type TA0314.
Diesel USA - The guy told me that the turbocharger was discontinued - well yeah, it has been a few decades I asked if he had a kit and he claimed he didn't.
eBay looks like the source at the moment.

Thank you again-

Knowledge is worthless unless freely shared .

The collective brain trust here is incredible .

So, you neglected to mention which ply you have.... radial or axial ? .

Follow the boost signal pipe to the I.P., it's attached by a banjo bolt that uses a 12MM ATF BOX WRENCH to loosen, loosen it (try to not drop the thin sealing washers) and with the engine hot idling hold it away from then up against the threaded hole, if the pipe is working the engine will slightly slow down as you move the banjo fitting away from the ALDA ~

If it does, no need to touch the pipe, relay or upper banjo bolt at the rear of the intake manifold .

GO SLOWLY HERE ! . this is a dead simple engine that's easy and cheap to diagnose and repair, it's very important to follow the proper order in looking for problems and fixing it too .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

True. My bad.
Radial: I estimate 1/8". Enough that if I place my ear within a few inches of the turbo, I can hear it move back and forth (left - right).
Axial: 0 as far as I can tell by testing.

Excellent!

Thanks for sharing your expertise with this.

Q. : how long has this been dripping oil here ? .

Most of the old Mercedes Diesels I see are soaking with leaked oil, you're looks pretty clean .

Even when mine was leaking I kept it clean so I knew where to start .

Maybe yours just needs some maintenance and an "Italian Tune-Up" to be good .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Around six weeks ago, I opened the wastegate for the first time in at least 23 years...could've been even longer. There was oil in there but certainly not what I would consider a large amount and the inside was not ugly dirty. At that time, I wiped away the excess but didn't do a thorough cleaning like what is shown in Picture 2 here from just a few days ago when I did clean it thoroughly.

Considering the radial play and the simple fact that the unit has almost 38 years of service and approximately 220,000 miles on it, a basic rebuild and the checks you mentioned above seem quite reasonable.

It's common to see a little bit of oil in the waste gates of these engines when blow-by is present. The 617 has a breather that feeds back into the inlet of the turbo, so oil vapor gets drawn in through the compressor and most of it will make its way into the intake, but small bits of oil will collect in the compressor housing of the turbo and drip down the hose to the waste gate. Unless the diaphragm is torn inside the waste gate, it's safe to just clean out and tighten up.

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Ah, great information - thanks for helping me to more clearly understand!

If a CA 1985 300D (yours?), blow-by gas is routed straight into the compressor. There is no oil separator and drain tube to the crankshaft as in the 1982-84 and 85 federal engines. Some people add an oil separator, aftermarket since common for all turbo engines. Some have a catch tank and some just drain the oil to the ground, thru the right spring tower hole.

I put a 1982 engine in my 1985 CA car, so rigged a drain tee to route oil into the crankcase via the tube which sits under the air cleaner in earlier cars. I could have easier installed the 1984- air cleaner but those shake & break. Indeed, I went the other way in my 1984, installing the 1985 CA frame air cleaner with similar oil drain. The compressor wheel was gunked when I rebuilt the turbo, but looks clean since. Even with the better oil separator in 1984- cars, some gets thru to gunk the air filter and get to the turbo inlet, especially in a worn engine with much blowby (say <300 psig compression and a dancing oil fill cap).

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans