Posted about a workmates 1995 Fiesta Si engine on saturday.
Car has done 95k

There was so much smoke coming out of the exhaust, that with an
oil consumption of only a 100 miles per litre, I had little
doubt
that the piston or rings were damaged on No 3 cy,.as when the
plug was diconnected, the smoking stopped.
But. Did a compression test today. No's 1 & 2 were a 145 psi, 3
& 4, 150psi.
With the amount of smoke, and those compressions I can't see the
pistons/rings being at fault, which only leaves the valve stem
seals, but personally I've never seen failed valve stem seals
cause the amount of smoke this car has. It's a thick choking
cloud. I'm surprised he hasn't been stopped.

His problems started some time ago, when he says the engine
gradually lost power. He continued to use it until it started
'popping' (his word) in the exhaust. Up to that time he hadn't
noticed any excessive exhaust smoke. He took all the plugs out,
No 3 was very oily and coked. Fitting new plugs didn't improve
anything (obviously) At that point he guessed he'd burnt a
valve.
He dropped it into a a small local auto repair shop, and asked
them to fix it. When he picked it up They told him they had
replaced one valve, and gave him a bill for £600!! Within hours
of picking it up it started smoking, so he took it back the next
day, and they said they'd fit a new valve stem seal. Picked it
up a couple of days later. It was no better. On taking it back
the third time, they did a compression check. Told him the
compressions were OK, then told him they had done as much as
they were prepared to do, and didn't accept any further
responsibility.
IOW get lost!.
That was about a month ago. Since then, he reckons he's put in
about £100's worth of oil.
AFAIC the garage didn't do the job properly, but the young guy
is not particularly assertive, and seems prepared to let them
get away with it, even though he hasn't really got the money to
fix it.
I don't know what you guys think, but IMO they've ripped him
off.
Charged him £600 and gave him back a car which is virtually
undrivable, and will undoubtably fail it's MOT in june.
TBH I feel sorry for him, but I don't want to get too
involved with his problem.
Mike.

"Mike G" <mgibbs (AT) clara (DOT) co.uk> wrote

Yes, it is a piston ring fault fault, and is becoming slightly less than
very uncommon on the Zetec E 1.6 engine just lately. If you strip the motor,
either you;ll find the oil control ring on no.3 broken up and in the sump,
or you'll find part or all of the piston skirt missing and in the sump! The
compression rings at the top will be present and working- which is why you
get good compression and it will fire on that cylinder no probs.

Not sure of the reason for failure, but judging on the recent other posters
comments, he had an engine with a failed thermostat which was allowing it to
run very cool, and habitually revving it hard- on what amounted to be a cold
engine. I am sure the piston slap caused the failure. - He had a broken up
skirt.

Tim..

" Tim (Remove NOSPAM." <the.farm (AT) NOSPAMbtinternet (DOT) com> wrote

You sure about that?
I'm not saying you are wrong, but IME that would be rather unusual.
That is, to break an oil control ring, on an otherwise undamaged piston.
O/c rings are not normally brittle. OTOH compression rings are made from
cast iron, so can break fairly easily, if piston damage leaves them
unsupported.
Mike.

"Mike G" <mikgibbs@tiscali dot co dot uk> wrote

I've not seen it in the Zetec E engine, but I have in acouple of others- one
was a Alfa TS engine which had failed pretty big style and the other was in
an old Ford cross flow with cast pistons which had done exactly as above-
run too cold- piston slap, and shattered the skirts on the pistons. Engine
ran well when hot (bad piston slap when cold) but smoked like hell, and only
when we dismantled it was the cause found.

Tim..