On Fri, 13 Feb 1998, Turner & Turner wrote:
> Why do some rocker covers have a breather pipe and some not?
On the TR2-4 4cyl engines, the early blocks had a breather pipe in them...
so there's no pipe in the rocker cover. It's just a tube, with a few
bends in it to stop anything fluid getting out, that is open to the
atmosphere.
Later on the pipe was installed so that the crankcase gases could go
through the PCV circuit instead of just into the open air; it's quite a
"distance" from the early vent point to the carbs.
> What's the purpose of a breather?
In your crankcase you have (in addition to many metal objects) some oil,
and some air. The oil is there to make things oily <g>-- the air is there
to give the breather something to do.
When your engine heats up the air expands... if it can't get out easily,
it forces the oil out. Enter the Mighty Breather! It allows your
crankcase to expel or intake air, as required.
...you can also get excess air in the crankcase if combustion gases are
getting past the piston rings (blowby)
Often the problems involving oil squeaking out the dipstick tube involve
an excess of air pressure in the crankcase.
Hope this helps,
-Malcolm
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