91 350SD Bad Head - Mercedes-Benz Forum

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post #1 of 2 (permalink) Old 12-02-2010, 08:03 AM Thread Starter
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91 350SD Bad Head

Well, here we go!

I've been reading this forum for about a month now while I've been deciding to tear down this engine. There seem to be a lot of knowledgable folks out there and I could use some advise.

Car has a little over 234000 miles, and I bought it non-running with an empty radiator. head casting# is 603 016 21 01.

PO sez "It suddenly quit running", yeah, welll.... no wonder.

After freaking out over the RodBender Posts I'm relieved to find that maybe all I'm dealing with is a bad head as there are a couple of unauthorized holes in it.

Inside of valve cover and timing chain cavity are remarkably clean and free of sludge. Exposed parts of cooling system seem clean as well. Maybe PO actually tried to take care of this car.

Inspection reveals water passages next to head bolts 9 and 7, between pistons 2&3 and pistons 3&4, have blown out toward block leaving no apparent damage to block. All pistons seem to be ok except #2 which shows carbon fouling I believe I can clean up. Small water passages in block between pistons 3&4 are very slightly clogged with aluminum from head but a drill bit will clean that out, its not stuck in there very tightly and didn't deform the hole.

Being at TDC, Pistons 1 and 6 are the same height at top of stroke .03" above block, pistons 2 and 5 are at the same height 2.95" deep, and pistons 3 and 4 are at the same height 2.88" deep. There is no visible scoring in any of the exposed cylinder walls. There is no significant ridge at the top of each cylinder. (I may not be EXACTLY TDC)

Inspection of charge air tube and charge air manifold are nasty with oil fouling/caking as is outlet of turbocharger leading me to suspect oil seal failure of TC. There is slight sideplay of compressor shaft with intake air hose removed.

Could it be that at failure, EGR System siphoned oil through turbo? Maybe, but that wouldn't explain caked oil in Charge Air tube. Seem to me to be a long time effect to produce so much gunk.

Non-removal check of water pump, spinning by hand, indicates there may be a problem here as well which may have been the initial cause of failure. The is no real friction per se, but the pump shaft seems to have a springy feel to it when turned slightly, as though a rubber seal might be sticking to the impeller shaft. Kinda feels like it may have a rubber impeller like a boat motor, if that makes any sense.

I have been searching for a used head and the info I have dredged up indicates that the 603.970 was used from 91-96 in everything labeled 3.5L Diesel, but some indications have been found that the same head was also used on the 3.0L Turbo Diesels too. The wrecking yards don't know, and the mercedes dealership was no help.

There is also the question of two different head gaskets being available for re-assembly, the updated one having a sort of zig-zag silicone seal path on one edge and it's predecessor being all straight lines.

Now you have all the intel I have, there are a few questions for the gurus out there:

Does the block seem ok to you?
Which head gasket to use?
What to ask for at the junk yard sites for a head, which years and models, which casting numbers 17 and up?
Water Pump seem funky?
Anybody want to sell me a good head and water pump?

Thanks in Advance for your help solving this.
Keith Richards
Dallas (sort of) Texas
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post #2 of 2 (permalink) Old 12-02-2010, 04:54 PM
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