Astra Mk 3 1.4 head troubles

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

 

It shouldn't do, there is a pressure relief valve in the header tank
cap. I'd fit a new cap while you are doing the repair, the valves do
fail.

 

A few photos of the eroded area of the head (No1 cylinder position) can be
found here:

http://www.imagebam.com/gallery/b7e01c64a021199e9866147d4619d54c

Is a head skim the correct solution for this erosion ?

The part of the piston adjacent to the blow has been cleaned of carbon
deposits by the coolant being turned to steam - steam cleaned. (the large
red flake on the pistion is a loose bit of gasket)

The photos of the block after cleaning are both of No1 cylinder, where there
appears to be significant erosion of the block. Similar block erosion is
found around other cylinders. Though the failure was on the head side it
looks as though gasket failure due to block erosion remains a possibility,
perhaps the block needs a skim too, but that's not on the agenda.

With so may cars of this age/model going for scrappage perhaps a replacement
engine is a more cost effective solution ?

Roger R

 

Time for replacement engine, replacement head or a replacement car.
Looks like a casting flaw or a porous head. Skiming probably won't help
but you could try and see what it looks like.
Dave

 

I had the head skimmed and it has come up perfect, with no trace of the
imperfection. Subsequently refitted the head and am keeping my fingers
crossed that all will be ok.

This blown gasket first manifested itself in the summer of 2008 as 'the
sound of running water' that I described in message:
http://groups.google.com/groups?as_umsgid=
It took eighteen months to become serious enough to demand rectification.

At the time 'me140' correctly diagnosed the trouble.

Inspection of the affected cylinder (No.1) did not show any untoward
problems. The piston crown was partly 'steam cleaned' clear of carbon, and
the inlet valve had a white coating that was also on the plug tip. The
white coating was soft and easily cleaned off.

Roger R

 

Have fitted a new cap as you suggested.

The valve in the old cap was stuck exacerbating the pressure caused by the
gasket blow. I don't know what pressure was reached, but it was sufficient
to expand the hoses so that all the coolant was pushed from the header tank
giving the appearance of empty, but when the pressure cap was removed -
slowly - with great air escape and gushing and gurgling, the level returned
to the correct level. The (new-ish) hoses are quite strong so it must have
been some pressure.

Roger R