[Mgs] MGA crankcase ventilation

Stan Fickes spridget at gmail.com
Sun Jul 14 13:05:00 MDT 2019

Thanks, Paul!
I concluded when I cranked the motor with no plugs installed and still felt
the pulsing air that it was not a compression issue. For completeness, I
need to try the same thing with the plugs installed, to see if there is a
difference. I just can't think what else would pump air into the
crankcase/rocker cover! I checked the draught tube this afternoon by
squirting some low-pressure air into the rocker cover tube, and felt a
gentle stream of air out the bottom. I should also check that with the
starter motor turning to see if it's consistent between the two tubes.

On Sun, Jul 14, 2019 at 4:31 AM PaulHunt73 <paulhunt73 at virginmedia.com>

> IME you should always hear some hissing when putting compressed air into a
> cylinder, ring sealing isn't perfect.
> Removing one plug at a time may show which cylinder or cylinders are at
> fault if the pulsing lessens.
> Air pulsing out of the rocker cover definitely indicates a major
> compression leak from somewhere, despite your compression readings.
> Having said that AFAIK an MGA should also have a 'road draught tube'
> hanging down from the front tappet chest cover, which is another route for
> air to pass in and out of the crankcase.  Perhaps that is blocked.
> PaulH.
> ----- Original Message ----- kcase ventilation
> I have an MGA 1600, under 2,000 miles since the engine rebuild. While
> working on an unrelated issue, I discovered that the front air filter was
> thoroughly soaked in oil. The source was the vent hose between the air
> filter and the valve cover. I found significant (to my lack of experience
> with this system!) pulsing air blowing through the hose at idle.
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