[xk-engine] Non Jag I6 question

XK-Engine
1

Perhaps someone can help me with a problem.

Ford Dagenham I6 in a Reliant Sabre. Head gasket was leaking, was
replaced, compression etc was fine and car ran well. When we
drained the oil it wsa full of coolant. Contact with the PO
confirmed that the car had a history of magically rising Oil level,
which was what made us look at the head gasket in the first place.

After some running the oil was replaced again, and the engine
seemed to be fine.

A couple of months later the owner was out for a run, said the
engine started making noise and the O/P ‘‘disappeared’’, constant
highway speed, he killed the ignition immediately and rolled to the
side. Took the pan off, no sign of water in the bottom, not even
surface rust, not lumps of anything solid or metallic in the pan,
but the #3 conrod bearing was toast, badly scored and with bits of
black build up, the throw on the crank wasn’t all that bad. All the
other crank bearings were perfectly fine and measure -0.020 which
is what is stamped on the bearing shells. Oil passages are all
clear as far as we can tell. Oil pump had nothing untoward inside
it, and shows only little sign of wear (has been replaced at some
point judging by the appearance, pressure relief valve seems to
operate without sticking. No sign of a massive pressure loss
anywhere else internal or external to the engine.

Why would just one bearing go? If the crank or it’s feed had a
blockage or feed loss I would expect all bearings, or at least all
the ones ‘‘behind’’ the leak to show similar damage. Not having been
there it is hard to tell just how bad the O/P went, I have trouble
believing that a single bearing going south would allow so much
flow that the O/P would fall off all that drastically.

One opinion is that the #3 bearing was just waiting to go south,
and it did so more or less without being directly caused by the
head gasket change, so we should just replace all the bearing
shells and button it back up, presuming that the owner’s attention
was diverted by an expensive noise and wasn’t really paying
attention to the O/P gauge as things happened.

The other opinion is that things don’t generally happen without a
cause which is reasonably easy to trace empirically, even after the
fact.

Andrew–
1968 3.8S
Zurich, Switzerland
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2

In reply to a message from JagWaugh sent Sat 8 Oct 2016:

As you mentioned coolant ingress, you could check the failed
cylinder very carefully to see if it shows any sign of
coolant ingress, such as being cleaner.

If it had coolant, it may have hydro-locked, which exerts a
lot of force on the conrod.

I know of cases where shortly after water getting sucked
into air intake, a broken rod or crank has occurred,
presumably the rod is twisted, or maybe the bearing gets
deformed–
The original message included these comments:

replaced, compression etc was fine and car ran well. When we
drained the oil it wsa full of coolant. Contact with the PO
Why would just one bearing go? If the crank or it’s feed had a
blockage or feed loss I would expect all bearings, or at least all

–
Tony
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3

In reply to a message from awg sent Sat 8 Oct 2016:

Hydro lock killed my son’s Dodge Stratus; one rainy night
the storm sewer was backed up and he ran into deep water
over the level of his air intake and it sucked in and broke
a couple of rods.

My 1950 Mark V pushrod engine blew a head gasket once, and
as it is a non-pressurized system I got oil in the
antifreeze, the whole top of the radiator was bubblin’ black
goo, like Jed Clampett’s Texas tea.

Back to the Dagenham. I would look for blockages in the oil
passages through the crankshaft; I presume it has threaded
plugs like an XK engine?–
XK120 FHC, Mark V saloon, XJ12L Series II, S-Type 3.0
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4

In reply to a message from JagWaugh sent Sat 8 Oct 2016:

Sometimes rods are ‘handed’ like many pistons, including
XK.No idea if the Zephyr/Zodiac six did, but maybe
something was assembled wrongly? Otherwise, blocked crank
drilling - maybextrmporaryvlike a silicone worm?–
66 ‘UberLynx’ D, 70 FHC, 79 S2 XJ12L, 97 XJ6L
Gaithersburg, Maryland, United States
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5

In reply to a message from PeterCrespin sent Sat 8 Oct 2016:

Thanks for the feedback.

I don’t think hydraulic lock was the issue, here’s why: when we did
the compression test and subsequently took the head off it was the
rearmost cylinder where it was leaking, but the trashed bearing is
3 cyls forward of that. If it were hydrailic lock I would expect to
see some evidence of hammering on the bearing of the leaking pot,
this was not the case. Given the amount of water that came out with
the oil it is a bit surprising that the internals weren’t a bent
rusty mess. The car has sat for the most part of the last 20 years,
with occaisional track day jaunts, so I would have thought that a
catastophy would have happened on the track if this was a pre
existing problem, even if only a marginal one.

When the new owner bought the car last spring it ran well enough,
but was just not as quick as one would think given how light it is.
We did a fair bit of fettling, mostly electrical, and some fuel
pump/filter fun, and such, and when we put the car on the exhaust
gas machine we couldn’t get consistent, values then we found the
leaking cyl. The carbs were all too rich (almost universal with the
antiques we see for the first time).

It wasn’t like the engine was running on only 4 cyls, it ran
reasonably smoothly, spun up relatively happily, it was just
developing a lot less power than one would expect - I always find
it hard to judge an engine/car which I am not familiar with, but
this car really was built as a track car.

Unfortunately I wasn’t about when the head was off, but the guy who
did it is a professional and one of the best engineers I have ever
known (even if he doesn’t like SU carbs and imperial fasteners). He
certainly would have noticed any clues while replacing the
headgasket, and certainly didn’t do anything wrong which would have
caused the conrod bearing fault directly.

1/2–
The original message included these comments:

Sometimes rods are ‘handed’ like many pistons, including
XK.No idea if the Zephyr/Zodiac six did, but maybe
something was assembled wrongly? Otherwise, blocked crank
drilling - maybextrmporaryvlike a silicone worm?

–
1968 3.8S
Zurich, Switzerland
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6

In reply to a message from JagWaugh sent Sun 9 Oct 2016:

2/2

We walked through the silicone worm question, but we didn’t find
anything in the pan, pump, or filter. A blockage in the crank (or
anywhere downstream from the pump) would be more likely to cause
the O/P to spike, rather than drop, and although the conrod bearing
is toast, it isn’t so bad that it alone would cause the O/P to drop
massively as the owner said it did.

Because he was the last one to touch the engine before the conrod
bearing went he is going to eat the labour cost to rectify this. at
the moment the engine is still in the car and the pan is off -
everything is fine except for this one bearing, and the oil passage
to that bearing is clear. What we are trying to do is decide if the
block needs to come out and go to a machineshop. Labour to remove
isn’t the big concern, what we are trying to do is determine if
this really needs to be done, as the machining work will be on the
owner’s tab, and he’s already of the opinion that the car has cost
him too much. Everyone is prepared to take a certain level of risk
by just changing the bearings out in the hope that the bearing went
as a result of the long term exposure to coolant, and that the
others would have gone if he hadn’t switched it off immediately
when it started making bicycle in a Moulinex noises.

If it was a handed or bent conrod, then it was that way long before
we noticed the headgasket issue, and the papertrace shows that the
car was campaigned in the UK for a couple of years after the engine
had been rebuilt, so it probably isn’t an assembly error, but
rather a wear or corrosion issue, but since none of us know this
engine we’re pretty much reduced to ‘‘Something went wrong, at some
point, and ultimately this bearing proves that.’’

The conrod bearing seems to be a symptom, but we’re not sure of
what what caused it. I was sort of hoping that someone would
say ‘‘You see that weeny little tube which sprays oil on the rocker
shaft? The end of it is supposed to be flattened off to a 1/32
opening, if someone has opened it up then the lack of restriction
causes oil feed problems to the crank’’

Andrew–
The original message included these comments:

1/2

–
1968 3.8S
Zurich, Switzerland
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7

In reply to a message from JagWaugh sent Sun 9 Oct 2016:

Perhaps none of us knows that engine well enough to say,
‘‘see that weeny little tube’’, but I have certainly seen
corroded bearing shells in an XK engine that sat for umpteen
years with water in the sump but was probably a good runner
before that. Perhaps rod #3 was at BDC during those idle
years and got the worst of it.–
XK120 FHC, Mark V saloon, XJ12L Series II, S-Type 3.0
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8

In reply to a message from JagWaugh sent Sat 8 Oct 2016:

The only time I ever let someone else change the oil and
filter on my E was some years ago with the garage on the
corner of our road after coming home one afternoon with an
early morning start the next day…an hour after the guy
had the car, I walked up to see him with the car over the
pit and asked if he had a problem…he replied he was having
trouble removing and fitting the O ring…I noticed there
was a lot of oil sludge on his hands…the next morning at
around 4am, I drove past a group of cottages about fifty
miles from where I started d and heard the unmistakeable
knock of a big end echoing back…on dismantling, only the
number two rod bearing was affected, I could actually remove
black from the scoring with my fingernail…must have been
one globule that was introduced on the filter change and
stayed intact until it was pressured into the bearing
aperture…those Ford V4 and V6 engines used to ingest water
from the inlet manifold as I remember, poor tolerances and a
tendency to round off the flats on the oil pump drive …–
The original message included these comments:

Perhaps someone can help me with a problem.
Ford Dagenham I6 in a Reliant Sabre. Head gasket was leaking, was
replaced, compression etc was fine and car ran well. When we
drained the oil it wsa full of coolant. Contact with the PO
confirmed that the car had a history of magically rising Oil level,
which was what made us look at the head gasket in the first place.
The other opinion is that things don’t generally happen without a
cause which is reasonably easy to trace empirically, even after the
fact.
Andrew

–
Keith.P. Series2 Roadster
exmouth, United Kingdom
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