Jim Grant's Tech Tips
'97 Ford Escort, Broken Piston
Q:
Ten days after the
"Service Engine Soon" light came on, my '97 Ford Escort would
not start. After several tries there came a loud noise from the engine.
The mechanic found a broken piston and two damaged valves. How can this
happen? There was no prior indication of a problem except for the Service
Engine Soon light being on. Could I have prevented this major expense
by having the car checked sooner? I had the" Check Engine" light
come on on occasions but the mechanic never found any problems. What is
the difference between the "Service Engine Soon" and "Check
Engine" light?
A:
There's really no difference
between the Service Engine Soon or the Check Engine light. They both mean
there is a problem that the computer wants to tell you about. As for your
engine failure we see that problem more than we care for. A closer inspection
of the engine should reveal that a valve seat in the cylinder head had
come loose. In the early stages this causes the computer to turn on the
check engine light to report a cylinder misfire. Sometimes it even causes
the warning light to blink and the driver may notice that the engine is
not running right. Then the problem can go away just as quickly as it
appeared and the warning light will stop blinking but remain on. The problem
with the loose valve seat is, in its infancy, it is difficult to detect.
The valve seat moves some and then goes back into place. All the while
the valve seat is wearing away at the part of the cylinder head that holds
it in place. Then when conditions are right the valve seat falls out enough
to hold the valve open and the piston comes up and slams the valve, breaking
the valve seat. The smaller, but not small enough pieces, are hammered
by the piston into the cylinder head. It is not uncommon for the fractured
parts/pieces of the valve seat to blow back into the intake manifold and
be pulled into another cylinder to continue the destruction. From the
time the valve seat drops to when the engine goes bang only takes a moment.
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