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Re: Seized engine

> >Monday night I drove my '88 325is into about 10 inches of water (halfway up
> >the stock wheels).  The car died, and would not turn over.  After getting
> >the car into a garage, I ran every electrical test I could think of,
> >concluded I had a bad starter, and replaced it.  No change.
> >
> >At this point, I tried to move the engine by turning the crankshaft pulley.
> >The crank was frozen dead solid.
> >
> >I can't imagine why a dunking would do this.  The car had not been running
> >more than 2 minutes, and had been started from dead cold.  There is no
> >external damage visible to the car or the engine.
> 
> What I suspect happened is that water went up your exhaust pipe into one
> of the cylinders, which now has both valves closed with a full charge of
> water in it. No starter in the world can compress water enough to let
> the engine turn over.

More likely is that water went into the intake.  The inlet for the air
filter on the E30 cars is right behind the left headlight.  Wading through
relatively high water can cause water to enter the intake, which in
turn can cause hydrostatic lock, if enough water got in.

Was the air filter wet?  A pretty reliable sign of water entry.

> 2. Worser case - when you first tried turning it over with the starter,
> it tried to compress the water. When this happens - it quite frequently
> will bend a connecting rod - making for a really broken engine. At the
> minimum - this will require a new connecting rod, wrist pin and connecting
> rod bearings - not a job for the home mechanic (usually).

The starter usually does not have enough power to bend the rods or
crankshaft.  However, if the car died because of water entry, then 
the inertia of the moving parts will very likely cause at least bent
connecting rods.  A lot depends on how high the revs were when the motor
died.  

> 3. Worstest case (and not as likely) - you also bent the crankshaft. The
> only way to really determine this is to remove the head and measure the
> deck height of each piston (how far below the head they come up). ALL should
> be the same, +/- a very small tolerance. If this is the case - I would look
> for a new engine, it just isn't worth doing a rebuild on an engine this
> damaged, parts and labor will exceed the cost of a short block.

Measuring the piston heights for a bent crank assumes that the connecting
rods are not bent.  The easiest way to get an idea if something major is
wrong is to first let the water out (pull the plugs and turn the motor over)
and then do a compression test.  Slightly bent rods will still allow the
motor to turn, but compression will be down on the affected cylinders.

Ben