Quote:
Originally posted by fields
So, is there a finite life to the aluminum head, or is it a result of overheating? How long can you expect the head to last?
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The aluminum heads used on the six-cylinder cars in 1986-87 ONLY (that's 300SDL, 300D, and 300TD wagon) had weak heads. If overheated, they are very likely to crack. The cooling systems tend to get corroded over the years, and fan clutches fail.... if not corrected, the overheating is possible if you don't watch the temp gauge closely. Or, stupid dealers tell people that if it's not "in the red", it's normal. I was told this by a dealer and later found out it's NOT TRUE. These cars should almost never get over 100C, if they do, something needs to be fixed. Could be simple, could be expensive, hard to tell. Frequent cooling system maintenance is important - not a big deal really. Also, most of the 86-87 cars had trap oxidizers, basically a catalyst on top of the turbo. This causes a serious heat load and one theory is that it contributed to the heads cracking. Another nuisance is that the head can be cracked, but no oil & coolant will mix! So many people rule out head or gasket problems due to that, which is wrong. The early warning symptom is very high pressure in the cooling system when the car is *stone cold* in the morning. Pinch the upper rad hose when cold, it should be soft. Note that this test is invalid if the car loses coolant and/or has a bad rad cap.
Anyway, some original 86/87 heads may never crack if the car never got too hot, and MB redesigned the heads so the replacements are stronger and won't crack. Look at the casting number below the #2 cylinder - 603-016-xx-01. If "xx" is 15 or less, it's the old/flawed head. If it's 17 or higher, it's the new/fixed head.
The 1990-up six-cylinder engines had good heads. All the 4 and 5 cylinder aluminum head engines are fine, there are no problems with those at all. If you can afford a 1990-95 E-class diesel, those are even nicer.... better MPG, no engine problems, but less power.
BTW - I prefer the interior of the 124 greatly over the 123, but that's just my opinion. The 123 is a little too "classic" for my taste, it's closer to "Spartan".
