On 09/13/2009 04:18 PM, Tegger wrote:
> Elle<honda.lioness@gmail.com> wrote in news:630825e6-6d37-4ea9-a3e5-
> 0d9ec77dc3b9@e12g2000yqi.googlegroups.com:
>
>> On Sep 11, 7:18�pm, jim beam<m...@privacy.net> wrote:
>>> also, do a common-sense blow-by test on the motor. �with the engine at
>>> working temp, carefully unscrew the oil filler cap. �if the engine's
>>> breathing right, and you don't have a compression/wear problem, you'll
>>> get a bit of chuff out of the hole, [and some oil spray]. �if there's
>>> something [badly] wrong, either the cap will want to shoot out of your
>>> hand as you get close to removal, or you can feel some vacuum if you
>>> have your hand over the hole. �what you /should/ feel is a reasonable
>>> degree of positive pressure.
>>
>> Did this test. No shooting of the cap at all, nor any vacuum. With my
>> hand on the fill hole, there was a pulsing positive pressure--chuffing
>> as you wrote--and oil spraying/slopping onto my hand.
>>
>> I gather this is not conclusive but a crude test for seriously bad
>> compression, right? I expect to get an inexpensive compression tester
>> soon and see what this yields.
>>
>
>
>
> Air jetting from the oil filler cap tells you nothing, I'm afraid. Even a
> brand-new engine, freshly broken in and at max oil life will exhibit
> /considerable/ jetting from the oil filler cap. From oil filler neck
> emissions alone, it's hard to tell the difference between the blowby of a
> worn engine and a new one.

sorry dude, if you have two same-model engines side by side, the
difference between worn and not worn is very much apparent from that test.


>
> You need to have a garage perform wet and dry compression tests. Keep in
> mind even these are only analogs for oil ring condition.

only tests compression, not oil control.


> It is possible to
> have good oil rings and poor compression rings, and vice versa.

indeed. see above.