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