Graeme's right about the leakdown test, and his diagnosis chart's right on.
A few further observations;
> Over time (a couple of minutes) you then observe whether and how much the
> compressed air leaks away.
Usually, we use a gauge with a small orifice in it, and supply compressed air
at 100 psi. Then, measuring the pressure on the piston side, you get a
straight percentage: if the supply side holds 100psi, and the cylinder holds
92, then you have "92% leakdown". But either method works.
If you really do have good leakdown and compression (the leakdown test really
can't tell you the condition of the cylinder walls, and the compression test
can do that) I'd suggest that the head gasket's NOT blown.
fwiw,
Toby
-------------- Original message ----------------------
From: "Graeme" <graemes@internode.on.net>
> "I'm looking for another test to confirm the inevitable. Any suggestions??
>
> JH Bahn "
>
> Hi there,
> your compression values sound good and there is a good balance over the 4
> cylinders.
> Another "non-invasive" test you can do is a Leak Down Test.
> This will pressurise each cylinder in turn with the piston at TDC and both
> valves closed.
> Over time (a couple of minutes) you then observe whether and how much the
> compressed air leaks away.
> There are only 5 possible paths: -
> 1)Faulty ex. valve, cylinder will fart into exhaust manifold, listen for
> hissing at tailpipe.
> 2)Faulty in. valve, cylinder will fart into intake manifold, listen for
> hissing at carb. Intake.
> 3)Blown head gasket, cylinder will fart into either oil passage or coolant
> passage, look for bubbles in radiator neck or listen for hissing at valve
> cover oil filler hole.
> 4)Broken rings, cylinder will fart into sump, listen for hissing at oil
> filler/dipstick hole or watch for a nice fountain of oil mist from these two
> holes.
> 5)Any where else it farts from!
> Obviously broken rings is not likely but if engine passes all the above,
> then thermostat/coolant circulation may be the culprit.
> It is possible to have the coolant circulating too fast thru the system and
> it will not have enough time to shed heat into the radiator.
> P.S. "FARTS" is a recognised technical term here in Oz.Regards,
> Graeme Suckling
> 1965 SP310
> 1971 P510
> 1972 PL510
> 1973 HS30
> 1993 ECR33 Skyline GTS25t
> http://www.imagestation.com/album/pictures.html?id=4291195515
> Adelaide
> South Australia.
|