740 oil filler cap leak?

  • Thread starter Thread starter Allen Lillie
  • Start date Start date
A

Allen Lillie

I am fixing up my 89 740, 175k, w single overhead cam, 4 cyl engine - I
notice oil spatter around the oil filler cap on the valve cover.

I replaced the flame trap, cleaned the throttle body, unplugged a clogged
vacuum line, replaced some cracked vacuum tubing. I replaced the oil filler
cap gasket, too.(the old one was like wood)

When the car is running and I unscrew the oil filler cap on the valve cover,
it bounces around, and I can see visible blow by. It does not get sucked
down by any vacuum.

Is this normal? I have heard that this was a way of testing the PCV system
for some models, not all.

Car is running very smooth, plenty of power. Do I leave well enough alone?
 
Did you check that the small pipe from the flame tap to the inlet manifold was
clear and clean along with the connection to the manifold (hollow brass
fitting)?

Cheers, Peter.

: I am fixing up my 89 740, 175k, w single overhead cam, 4 cyl engine - I
: notice oil spatter around the oil filler cap on the valve cover.
:
: I replaced the flame trap, cleaned the throttle body, unplugged a clogged
: vacuum line, replaced some cracked vacuum tubing. I replaced the oil filler
: cap gasket, too.(the old one was like wood)
:
: When the car is running and I unscrew the oil filler cap on the valve cover,
: it bounces around, and I can see visible blow by. It does not get sucked
: down by any vacuum.
:
: Is this normal? I have heard that this was a way of testing the PCV system
: for some models, not all.
:
: Car is running very smooth, plenty of power. Do I leave well enough alone?
:
:
 
Yes, the brass fitting (aprox 1/8" ID) was plugged, and I cleaned it. I
also replaced the hose that connected the flame trap and the fitting.

I sort of cheated in cleaning the throttle body: I held the butterfly open
and sprayed it with carb cleaner, wiped it out with a rag. Is it worth
taking off the throttle body to do a more thorough job?
 
It is certainly worth wile doing a thorough job. You may use nearly a full can
of carb cleaner but you will have an as new throttle body which will last
another couple of years.

Sometimes it is a sign that the cap seal/gasket is a bit tired and needs to be
replaced, it could also mean that a bit of bore wear is becoming noticeable. It
is not enough to worry about until you get large amounts of oil being blown past
the cap seal.

Cheers, Peter.


: Yes, the brass fitting (aprox 1/8" ID) was plugged, and I cleaned it. I
: also replaced the hose that connected the flame trap and the fitting.
:
: I sort of cheated in cleaning the throttle body: I held the butterfly open
: and sprayed it with carb cleaner, wiped it out with a rag. Is it worth
: taking off the throttle body to do a more thorough job?

<snipped>
 
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