I am new to the forum. I have a '94 e320 wagon (92k) and an '87 190e 2.3 (141k). I want a diesel and I am considering purchasing an '87 300D Turbo with 168k miles. It appears to be well maintained and I was curious if anyone had comments on what to look out for; also, I understand that this was the one and only year MB imported this 6 cylinder diesel engine -- anyone know why?
thanks for your help.

It was imported in 86 and 87.

The one big thing to look out for is a cracked head. Do a search for "603" (the engine number) and "cracked head". There is a way to tell by the casting number if it is upgraded to a more bullet-proof head or not. The above search should net you where to look and what numbers to look for.

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Keep everything as simple as possible-but no simpler--Albert Einstein

Welcome to the forum.

Yes, 1987 was the only year that the 603 engine was utilized in the W124 body. The engine was used in 1986 and 1987 in the W126 body. It was discontinued in 1988 and 1989 for emissions reasons and appeared again in a 3.5L configuration in the W126 in the years 1990-1995. It did not return to the W124, however, it's smaller five cylinder brother, the 2.5L, did grace the later W124 vehicles.

As mentioned, you need to confirm, to the best of your ability, that the head is not cracked. It's not easy to verify this without an oil analysis, but the best test is to look for pressure in the cooling system after the vehicle has been run and then shutdown for 12-24 hours. Squeeze the upper hose. It should feel soft and you should easily squeeze your fingers together. Now, if it feels firm, then open the cap on the expansion tank. Squeeze the upper hose again. If it now feels soft, then pressure has been relieved from the system. Make a 180° turn and run away fast.

This test is not a guarantee of a cracked head, but, if the symptom appears, you don't want to risk purchasing the vehicle.

Naturally, any oil in the coolant reservoir is grounds for an immediate rejection.

When it's running, open the oil fill cap on the top of the valve cover and set the cap back loosely down on the opening. If the cap will sit on top of the opening, vibrating slightly, the engine is acceptable. If the cap gets blown right off the opening , the blowby is probably more than you wish to accept.

I'm also looking at 87 603s. Great tips fellas, THANKS!

Couple of questions though:

1. Where in the head will I see the casting #? Is this visible by just opening the hood? I looked up the two versions: 14 was the one prone to failure and 22 was the revised one.

2. If there is oil in the coolant resv., will it be separated from the coolant and sitting on top? on the bottom? or will it mix into the coolant?

1. It's visible if you have a pocket mirror. It's on the driver's side of the head directly below the crossover.

2. If there is oil in the coolant reservoir........you'll know it instantly.......if you need to ask the question........there is no oil (of any consequence) in the reservoir.


Perform the check for pressure in the cooling system........it's one of the earlier symptoms........way before you ever get oil in the coolant. Sometimes you don't get any oil in the coolant.......just coolant in the oil...........and you'll need an oil analysis for verifying that.

Brian....
not sure I understand the "upper hose test"...can you explain it further....

Sure.....

After the engine is shutdown and it sits overnight, a normal engine won't have pressure in the cooling system.......in fact.....it will probably have slight vacuum.

An engine with a crack into the cooling system will pressurize the cooling system and the pressure will remain overnight. So, the upper hose will feel very firm when you squeeze it. Then, open the cap, squeeze the hose again, and see if it is now soft. If the pressure came off.........which would also be noticeable by the escape of air upon cap release........the hose will now be soft.

A classic sign of either a bad head gasket or a cracked head. But, you can't tell which is the culprit........however on the 603, the odds are not in your favor.

Does the 602 suffer similar head-cracking problems?

- Jeff Miller
190DT (with replaced head)

AFAIK, it does not.

Thanks.

- Jeff Miller
190DT

Just thought I would add that number 17 heads are good as well. They came on the 3.5 liter engines and are not known to crack.

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Keep everything as simple as possible-but no simpler--Albert Einstein

I've heard that some 602's have suffered head-gasket failures....

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1960 MB 190Db w/ full sunroof
1985 Toyota Pickup
2006 Honda Odyssey EXL R&N
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