400 oil leak

[Hydroglen]

Hello,
My 400 has always had an oil leak /seepage coming from the head. This is seen as oil around the head near the head bolts and spark plugs. It oozes out of the left side of the head.
I have cleaned the head many times but I am at a loss as to were it is coming from. After cleaning I have tried running the engine wilst observing and some 15 minutes later nothing.
It is not enough to see a steady leak.
If I go for a drive of say an hour, then I will find wetness and some streakes out the left side.
The rocker covers are not leaking. The cross tubes are not leaking.
I could perch myself on the left fender and have my wife drive the car wilst I observe. Before I go that route, I was wondering if anybody else had some thoughts on the subject.
Thanks
Dorien

[Ashley James]

Dorien
Is it coming from the join in the rocker cover behind the Distributor.
Mine is the same and I'd assumed that's where it's coming from.
Ash

[Hydroglen]

Well Ash now that you mention it it is worse in that general mid point
area. I can look more carefully in that spot, however......it does not
totally explain how I get pretty much the whole surface wet with oil. By
the surface I mean around the head bolts, spark plugs and in between.
It is bad or good enouh ( depending on your viewpoint) that from a clean
head, I get a dirty one in about 1/2 hour driving maybe 3/4 at the most. It
would mean that the oil is working it's way back up inside away from the
Distributor.......I suppose the fan's air flow might do that....hard to say.
Thanks for the suggestion.......will do some checking.
Dorien

[Geoff Dowdle]

Dorien,
Most 6 cylinder Brisol engines leak oil around the spark plug area and it
then runs down the left hand side of the engine .
I believe it is usually caused by the cross tubes leaking (they are just a
press fit into the head and relatively loose. ) .
Some tubes are damaged by previous" so called experts " using the wrong
spanners to remove and refit the head , and might need replacing .
It is also possible that the head castings are porous .
To help cure these problems ,here in Australia , we have the head sealed
with a clear Loctite solution in a refrigerated vacuum chamber by the
importers of Loctite.
It sucks any air out of the casting and replaces it with the sealing
solution, it sets when the head comes up to air temperature.
Make sure all the welding & machining has been carried out on the head
before this process is done as I'm told it is difficult to weld porous heads
after this treatment.
Then I use another Loctite solution around the cross tubes for extra
protection , but it is probably not necessary .
With all the above there is still no guarantee of a perfectly dry head but
it certainly makes a big difference.
Good luck
Geoff Dowdle

[Bellerophon]

The aluminium cross tubes are held in the head by the ends of the tubes
being spun over (or swaged if you understand that better). The holes in the
casting have a seat machined at each outside end so that after the tube has
been pressed in the ends are turned over using a tool, just like riveting.
This is fine when the head is new, however, with the constant temperature
changes it tends to work the tubes and low and behold we develop a leak.
When they were made no one thought that they would have to stand up for fifty
years, although today an alternative method may be used.
Geoff's solution of sealing with a solution seems good providing that you
can remove any oil that might be trapped between the tube and head. Due to
the closeness of petrol it is no good trying to glue the outside joint with
say Araldite as that would soon become detached.
The solution which the De Havilland Aircraft Company used on the crankcases
of their Gypsy aero engines to sort out any problems with the castings
made by the Stirling Metals, was to place them in a heated autoclave (an oven
in which it was possible to obtain a vacuum). When the castings were up to
temperature a special solution which set when cold was applied to the
castings and when the air was let back in it forced the solution into any holes
or porosity thus rendering it sealed. They were then pressure tested before
any machining took place.
My answer would be to re-tube the head, however you would need to make to
tool to turn the ends of the tubes, but one thing some brave person may try
is to make a bolt with angled ends which one could insert and turn and
tighten so that the ends are compressed, food for thought.
My regards,
Bellerophon

[Ashley James]

I've just checked mine and
it is one, possibly two push rod tubes weeping slightly. I'm not
sure how they were sealed but I know the head was "resin sealed"
which sounds like the Loctite process.
I don't think I'll try swaging, far better IMO to use a good modern
method. Loctite or a high temperature silicone I'd have thought would
be more reliable and easier to apply.
I've got a 2,500 mile trip at the end of May so I'll keep an eye on it
for now.
Presumably the head can stay on?
Ash

[brianjgkidd]

At Lotus Engineering, I was involved in the development of the LT5 V8 engine for the Chevrolet ZR1 car. GM Chevrolet were fanatical about the oil-tightness of their engines . Dripping of oil on a driveway was seen as a heinous crime. Mercury Marine, who manufactured the production LT5 engines, used Fluorescent Leak Detection as part of their pre-delivery engine tests. This uses a U/V lamp with a fluorescent dye in the oil to detect the smallest leak. Mercury were adamant that the dye was harmless to the performance of the oil, and the technique was approved by GM-but quite difficult to get rid of all traces of the dye as I recall.

And, of course, you may well wind up tracing leaks EVERYWHERE!

Go to www.tracerline.com for further info.



Brian Kidd

[Hydroglen]

Thanks for all your input / suggestions. The crossover pipes / tubes are
nice and dry as mentioned in my first post. Probably the driest part of
the head. I had checked them years ago and fixed a couple that were
leaking slightly. I sealed them from inside the rocker boxes.
I have lived with this seepage for years, but it may be getting worse, or in
my old age I forget what it was like and beleive it is worse lol!
I think I will work around the Distributor area and see about some leaks
there. Then see about a resealing when I need to take the head off. When I
take the head off I will probably want to take the pan off so as to remove
the pistons for new rings as we do smoke a little. And then I will see
something else......and and....
Perhaps some of you can explain this sealing issue. I understand the sealing
and vacuum process with Loctite or other solutions. What I don't follow is
that there is no water leaking and that is part of the head and even under
some slight pressure.
The oil is only in the rocker boxes and it is draining back in to the sump
and so not in the spark plug area. What is seeping at the spark plug area?
We are over the combustion chamber and beside the head studs......not an
oily area......I could understand water perhaps but not oil.
What am I missing ?
Thanks
Dorien

[Ashley James]

Dorien
Those heads can be so porous that if the water jacket is pressurized,
bubbles will appear on surfaces that look good. In particular around
number one cylinder behind the water pump. If you take the head off, a
local engine shop will be able to help.
If oil appears to be leaking from the Distributor shaft area, it is
usually from the join in the rocker cover behind it and some care plus
a decent gasket cement (Loctite Grey 5699) will seal it.
If your going to get pistons out I'd remove the engine completely
because they need to come out and go back from the bottom, although I
think you can push them far enough up to get the gudgeon pin out. It
is all a fiddle.
I'm doing a 4.5 L Bentley engine now for relaxation! The biggest
problem is weight and I'm getting old.
Ash

[Hydroglen]

Ash,
Ok understood and will try the Loctite and that may take up a good part the
oil leak / seepage. Re pistons coming out, is something that I will do only
if I have to. So far I am at about 300 miles / lit oil 40w , and with
excellent oil pressure, I hope I am OK for some time.
At that point I would probably tidy up the 100A engine and put that in.
Thanks again for this chat pages input on bearings and now I have bought
spares.
I am used to the fiddle of rods up from the bottom and pistons down and
sliding the pins in flush with the block. Alfa 6C engines are like that.
Sorry about the weight of the Bentley bits and age creeping up. I am
playing with a Knight sleeve valve engine. Parts are also pretty heavy.
We will never learn.....but the alternative to getting old is not that
attractive!
Dorien

[Geoff Dowdle]

Bellerophon,

> The cross over tubes that I have replaced ( mainly 85A & 85C) are not
> as
you describe . I always thought it was the case but the tubes are just
plain
parrallel sided tubes with the ends counter bore on about 30 deg angle .
The
head has a matching tapered area past the end of the tube . I can only
assume in production that once the tube is pressed in , a taperted cutter
is
used to form the matching counter bore in the tube and head.

I have considered machining a groove in the head near the ends of the
tubes
to fit a small "O" ring to get a positive seal .

"Bellerophon" is that your name ??

Regards
Geoff Dowdle

[Bellerophon]

Dorien, with reference to your oil problem, first the distributor, there is
an O ring on the stem which locates in the aluminium housing this is easy to
change. Second check the clearance of your valves in the valve guides, this is
also a place were excessive oil consumption can generate from. One can buy
replacement valves of 8mm diameter and ream out the existing guides, however,
you need a non standard reamer in order to achieve the correct valve stem
clearance.
The rockerbox joint behind the distributor is a source of leaks if not
fitted correctly, the safest way to do this is to fit the back section first
pushing it to the centre of the engine as you tighten the screws. The centre joint
should be fitted with the help of a jointing compound, and the front cover
pushed to the centre of the engine while the screws are tightened. This should
give you an oil tight joint, but if the gaskets are new retighten them as
they will copmpress with time.

My regards,
Bellerophon

[Bellerophon]

Geoff, Your idea of fitting an O ring is of course the best solution to the
problem, however, putting a groove in the head is not an easy job. There may
be two other alternative ways to do this which would be easier, first there
is enough clearance to roll two grooves in the aluminium tube to take some thin
section O rings. Second it would be possible to fit longer tubes and fit O
rings on the ends, then roll the ends of the tubes over to trap the O rings.
I have no idea why they should machine the ends of the tubes in situ when
the ides was to seal them against the head.
My be you can let me have your email address and will contact you direct,
_pegasushunter-at-aol.com_ (mailtoegasushunter@aol.com)

My regards,
Alan Blackwood
Bellerophon

[seanmcs]

Referring to Geoff' question, perhaps there is a whole tribe of
Bellerophons, seeing that we all ride on a Pegasus badged steed!

Sean

[Ashley James]

At a guess I'd say that Loctite 18034 would be the most efficient
means of sealing push rod tubes in a 2 Litre head. However and
depending on how loose they are, it may be just as satisfactory to
use a high temperature Silicone adhesive. My problem is that the RS
catalogue lists vast numbers of different ones without it being
clear exactly what the difference is.

In my experience it they are steed with a propensity for loosening
their nuts and bolts and leaking oil!


Ash

[Geoff Dowdle]

Alan,
Thanks for your reply.
"O" rings should be the best solution when they are new , but as you know
they can go hard over time with heat .
I'm happy just sealing them with a Loctite solution and once in a while
degreasing the engine as a part of the regular maintenance of the car .
Regards
Geoff Dowdle
darin-at-wix.com.au

[Hydroglen]

Thank you all for your suggestions. I will be reasealing the area behind
the distributor more carefully and following the tightening procedure
suggested.
Regards
Dorien

[Kevin H]

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