R
Roger R
Mk 3 Astra 1.4 SOHC 14CNZ engine.
Blown head gasket into coolant.
With the head removed the point of failure is a small imperfection in the
head in the circle where the gasket forms a ring around the cylinder. The
imperfection is a very small nick - only a fraction of a mm wide and just as
long as the gasket ring is wide -about 3 mm, and fraction of a mm deep.
Please advise:
Is head skimming normal practice these days or am I looking at a new head ?
Thanks.
The anecdotal tale:
Problem initially developed with gas getting into coolant system evidenced
by slight drop in coolant level over 500 or so miles. The cause of the
trouble was not at that stage known for certain, though suspected. A red
herring came along in the form of coolant found filling the recesses of the
gearbox casing, suggesting a leaking hose. Hoses were replaced and clips
tightened and subsequently checked tight but still the coolant appeared on
the gearbox. Quite lot of coolant - about a pint - had gone from the
system, but none could ever be found escaping, and it was really hard to say
where it was escaping.
On those occasions removing the coolant header tank cap the pressure was
found to be very great, much more than expected. Eventually, no matter how
tight the hose clips, the coolant still escaped somewhere and system
pressure became ...astronomical. The build up of pressure in the system
would occur after even the shortest run, not far enough to get the engine up
to temperature. But the odd thing was the pressure did not go down when
left overnight.
There was on occasion, some lumpy running on start up probably due to
condensate on the plug in the faulty cylinder.
Checking the oil filler cap - yellow goo indicated water in the oil and
blown gasket confirmed.
The action in the defective cylinder: On the power stroke, gas forced
though the faulty gasket into the coolant system building up the pressure
significantly. On the induction stroke coolant forced into the cylinder due
to the excess pressure build up in the header tank. Presumably this
pressure would eventually build up to something like cylinder pressure and
one hose or another would blow off or fail, resultant loss of coolant
causing overheating, bringing the vehicle to a halt - no doubt on the
motorway, in the dark, in the rain.
Roger R
Blown head gasket into coolant.
With the head removed the point of failure is a small imperfection in the
head in the circle where the gasket forms a ring around the cylinder. The
imperfection is a very small nick - only a fraction of a mm wide and just as
long as the gasket ring is wide -about 3 mm, and fraction of a mm deep.
Please advise:
Is head skimming normal practice these days or am I looking at a new head ?
Thanks.
The anecdotal tale:
Problem initially developed with gas getting into coolant system evidenced
by slight drop in coolant level over 500 or so miles. The cause of the
trouble was not at that stage known for certain, though suspected. A red
herring came along in the form of coolant found filling the recesses of the
gearbox casing, suggesting a leaking hose. Hoses were replaced and clips
tightened and subsequently checked tight but still the coolant appeared on
the gearbox. Quite lot of coolant - about a pint - had gone from the
system, but none could ever be found escaping, and it was really hard to say
where it was escaping.
On those occasions removing the coolant header tank cap the pressure was
found to be very great, much more than expected. Eventually, no matter how
tight the hose clips, the coolant still escaped somewhere and system
pressure became ...astronomical. The build up of pressure in the system
would occur after even the shortest run, not far enough to get the engine up
to temperature. But the odd thing was the pressure did not go down when
left overnight.
There was on occasion, some lumpy running on start up probably due to
condensate on the plug in the faulty cylinder.
Checking the oil filler cap - yellow goo indicated water in the oil and
blown gasket confirmed.
The action in the defective cylinder: On the power stroke, gas forced
though the faulty gasket into the coolant system building up the pressure
significantly. On the induction stroke coolant forced into the cylinder due
to the excess pressure build up in the header tank. Presumably this
pressure would eventually build up to something like cylinder pressure and
one hose or another would blow off or fail, resultant loss of coolant
causing overheating, bringing the vehicle to a halt - no doubt on the
motorway, in the dark, in the rain.
Roger R