<VV> Crankcase level rising

[Tony Underwood]

At 06:54 AM 2/10/2007, Doug Mackintosh wrote:
>Need a little advice from all you experts! This is not intended to 
>fuel the electric vs. mechanical flames, it's just a coincidence!!
>
>   This all relates to my 1962 Monza 102 HP daily driver.
>
>   I check my oil every time I refuel, and when I did so yesterday I 
> found the oil level had increased and was well above the full mark. 
> I also noted that my fuel mileage this tank was much worse than 
> usual (depending on the weather and type driving I usually average 
> between 19 and 24 MPG, this tank was around 14 MPG).
>
>   I expect I have a leaking diaphragm in the pump overflowing into 
> the crankcase. I replaced the pump with one purchased in 2003 from 
> one of our vendors. The provenance of the old pump was unknown. The 
> reason for pump replacement then was the same (crankcase filling up).
>

Sounds like you got a "bogus" pump with the unreinforced 
diaphragms.   They can almost be depended upon to leak sooner or 
later, usually sooner.


>   I assume the current pump has the raised anti-flowback bump in 
> the lower casting, so I would expect a leaking pump to squirt out 
> the back relief slot and not flood the crankcase. However, I see no 
> evidence of external leaks.


If the bottom diaphragm (the one intended to seal the rest of the 
pump workings from the crankcase) fails, you get fuel in the 
crankcase and not necessarily out the vent hole... depending on the 
manufacturer of the pump.   Some were different than the original 
Delco pump.


>   Note that I just finished a tuneup about 200 miles ago, the car 
> starts and runs beautifully, there are no external fuel leaks and I 
> have no reason to think fuel is flooding the engine through the 
> carbs (e.g. stuck float needles etc).
>
>   Before I start tearing into it today I have two questions:
>
>   QUESTIONS:
>
>   1) Does anything other than a pump leak make sense as a cause of 
> my crankcase level rising?


No, not without a lot of other indications such as running extremely rich etc.


>   2) If a pump leak is causing it, why is it not leaking out the 
> external weep hole in the back of the pump?


First:

Before we get any farther, have you retorqued the pump 
screws?    They *do* require this a time or two during the first few 
hours of running.    Snug 'em up and see if you have any more issues.


However, if it were my pump I would *Certainly* check it closely to 
make SURE it has fiber reinforced diaphragms.   This can be done 
easily simply by checking the edges where the diaphragms extend 
outside the castings.    If there are no fibers in the diaphragms, 
replace the pump.   Period.   No excuses or explanations.   And make 
sure the replacement pump *does* have fiber reinforced diaphragms.


The correct pump, once it's settled in and screws resnugged after a 
few days of running, will last for decades.    But you do have to 
retighten the screws after the pump settles in.    Check yours out, 
see what's what.



tony..