1995 Oldsmobile 88 Crank Bearings

Tiny
JASOND69420
  • MEMBER
  • 1995 OLDSMOBILE 88
  • 214,000 MILES
I am having an oil leak issue coming from my crank (3.8 v6 with a/c) I changed the seal 3 times I changed oil sending unit and checked the timing gear cover for cracks and inspected the gears and chain I even checked the harmonic balancer for cracks or anything and I even put a "crank jacket" on only I am still losing oil out of my crank.A mechanic told me the crank bearings should be changed only im not sure of that also recently the engine blew a head gasket I rebuilt the top end and that"s all I have done anyway I have never changed the bearings and if I do this is it a complicated job to do and does that even sound correct to you. Thanks for any help with this issue.
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Saturday, July 6th, 2013 AT 1:51 PM

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Tiny
CARADIODOC
  • EXPERT
What he is referring to is the thrust bearing. That is one of the crankshaft bearings that has sides on it to limit how much the crankshaft can walk back and forth. I don't think that's you're problem. Ford had a problem with their police engines around 1972. When the crankshaft walked too far the counterweights could hit the engine block webbing and make a loud knocking noise. Chrysler had a problem with their first 3.3L crankshafts in 1989 and 1990. They weren't hardened enough and the thrust surfaces would wear away. The symptom was always the same. The engine ran fine and was very quiet but when it moved back far enough it pushed out the rear main seal and there was a pretty good oil leak from the back.

You can see the hub on your harmonic balancer is pretty substantial and the crank would have to walk a lot before it exposed the seal. You might try using a pry bar to push and pull the crankshaft to its extremes and see how much that is. You'll hear a little knock and see a little movement but it shouldn't be excessive.

The first thing I would do is look for a smoke machine at the auto parts stores that rent or borrow tools. That will let you inject white, non-toxic smoke into the dip stick tube under 2 psi, then you watch where it sneaks out. That will work if the leak is at a non-pressurized place like a pan gasket or timing cover gasket. The smoke may not get through a pressurized passage if there's oil sitting in it. For that you can add a small bottle of dark purple dye to the oil. Run the engine without putting all the covers back on, then you search with a black light. The dye will show up as a bright yellow stain that you can follow back to the source. It works well to locate hairline cracks, especially those that only open up when the oil is under pressure or the engine has warmed up.
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Saturday, July 6th, 2013 AT 3:19 PM

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