At 04:14 PM 6/10/2000 -0700, Engelhardt wrote:
>Finally got the car on the road after fixing a blown head gasket. I got
about three miles from home, started up a hill, alll of a sudden a loud,
heavy clank started in the engine. .... The clank sounds like a heavy
hammer hitting an anvil but the engine still runs! I'm thinking maybe I
broke a con rod or the crank. Will the engine still run with a broken
crank? ....
It is possible if the crank is broken in the right place. This one:
http://www.ntsource.com/~barneymg/grapes/grapes1.htm
ran well on gentle throttle (although somewhat noisily) for about 40 miles
after it broke, and probably could have run much farther if it had to. But
if the break is any closer to the flywheel, you're probably out of luck on
that count. Aside from having to find a replacement crank, the repair was
just gaskets and bearings and reassembly.
On the other end of the scale, the next one I encountered broke just ahead
of the flywheel and nearly totaled the engine internally, costing several
hundred dollars to repair with me doing all the work except for machining.
Considering that you just replaced a head gasket (and without knowing the
details), there is a possibility of hydraulic lock in one cylinder caused
by coolant filling the combustion chamber. But that case should be quite
obvious, as it would certainly be accompanied by voluminous clouds of white
steam (water vapor) escaping from the tailpipe.
Otherwise very sudden onset of loud knocking is usually something broken,
could be several things, just think of everything the moves inside of your
engine. Crankshaft, con-rod, big end bearing cap, piston, camshaft,
tappet, pushrod, rocker arm, valve or valve spring (I recently had several
of these things all at once), timing chain or sprockets or tensioner,
distributor or drive gear, oil pump or drive gear, flywheel or ring gear,
clutch pressure plate or release bearing or release arm. If it actually
still runs well it's probably not a valve or piston, but otherwise you most
likely won't figure it out without at least some disassembly. Check for
external mechanical parts failure first, generator pulley, water pump, etc.
Then do a compression check, and if that checks out okay I think you're in
for at least pulling the oil pan for a peek inside.
Good luck, and keep in touch.
Barney Gaylord
1958 MGA with an attitude
http://www.ntsource.com/~barneymg
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