On Wed, 10 Sep 1997 14:33:50 +0200 "EPMD- Van syckel, John"
<vansyck@hq.1perscom.heidelberg.army.mil> writes:
>..... my B suddenly overheated. Pulled into a place where I knew I
could get water, waited until it cooled down enough to take the radiator
cap off. Topped it off (a lot had boiled off) and drove the last two
miles home. Same thing happened.
Jay,
You lost the water in just two miles? That's pretty fast, so should be
pretty easy to find the cause. Start with the easiest checks first (and
the most obvious). Start by checking that the fan belt is in place and
properly tightened, and that the water pump can turn.
Best way to test for leaks is with a cooling system pressure tester. Top
it off with water, put the tester on in place of the radiator cap, pump
it up to about 10 psi and see if it holds pressure. If you do not have a
pressure tester, top it off with water, put the radiator cap on, start
it up and let it run for three minutes or until the temperature gauge
hits the high end, or until it starts to steam, whichever comes first,
and shut it off. Check to see where water is running out (if any).
If it does not hold pressure, you need to find where the water is leaking
out. First suspect is the front seal of the water pump, where water
would be running off the bottom of the pump or off the belt pulley. Next
likely is a leaky hose or loose clamp, so check the radiator hoses and
the heater hoses. You might have a bad radiator cap that doesn't hold
pressure, but that shouldn't cause it to overheat in just two miles.
Also possible is a leaky radiator, but you also usually wouldn't loose
the water that fast.
A worse cause would be a blown head gasket. It's possible for water to
leak to the outside around the bottom of the cylinder head, but that's
usually a slow leak. More likely water may leak into the cylinder(s),
and can do so very quickly. Remove all the spark plugs and crank the
engine over while watching for water that may come blowing out of a spark
plug hole.
The worst case would be a cracked cylinder head (or engine block).
Diagnosis is the same as the previous paragraph. Also pull the dip stick
to see if you may have any water in the oil.
If it does hold the pressure, the most likely problem would be a stuck
thermostat, causing it to boil for lack of circulation. Next likely
would be the impeller on the water pump broke or came loose from the
shaft. Also possible is a lot of garbage in the radiator or water jacket
stopping off the circulation, but that's not likely to come on suddenly.
To check the radiator, remove the bottom hose and run water in the top
with a garden hose. The water should run out the bottom as fast as you
can put it in the top.
To check the thermostat, remove the top radiator hose, then three nuts on
the water outlet housing at the front of the cylinder head, and remove
the cover and the thermostat. Put the thermostat in a pan of water (deep
enough to cover the thermostat), and heat it to boiling. The thermostat
should open fully, wide open, before the water boils. If the thermostat
does not open, install a new thermostat.
If the system does hold the pressure, and the radiator is not clogged,
and the thermostat does open properly before boiling temperature, then
(as a matter of convenience) you might like to check for free flow
through the engine water jacket next. Run water in through the
thermostat opening with the garden hose. It should run out through the
water pump inlet as fast as you can pour it in the top.
If all of the above checks out OK, then it's time to pull the water pump
to have a look at the impeller. For this you will most likely have to
remove the radiator first, then the fan blade and water pump pulley, then
the water pump. If the impeller looks to be complete, still in one
piece, and still firmly attached to the shaft, it's probably OK. At that
point the world has come to an end, because I don't know of anything else
that could make an engine lose its' cool that quickly.
Keep us informed. Let us know what you find.
Barney Gaylord
1958 MGA with an attitude
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