This is interesting, but how does the tester work with only one gauge.
As in Eastwood's 46049. Do you have another source?
Thanks
John Uloth
74 TR6
"Robert M. Lang" wrote:
>
> On Mon, 17 Dec 2001, Peter Macholdt wrote:
>
> > Bob,
>
> Hello.
>
> > I understand the principle of the leak down test. Is there a good how to
> > source for the backyard mechanic?
>
> The process itself is fairly straight forward... read on.
>
> > How about any special equipment?
>
> You need a "leakdown tester". These are available from various sources,
> figure the cost to be between $60 and up. You get what you pay for.
>
> Additionally, you need a compressor to provide air pressure to pressurize
> the system.
>
> In essence, the leakdown test looks like a gas pressure regulator valve
> with two guages, line pressure and cylinder pressure.
>
> The process of testing involved rotating the motor to TDC for the cylinder
> that you are testing, removing the sparking plug and inserting the
> leak-down tester hose in place of the spark plug. You then open the valve
> and note the line pressure and the cylinder pressure. If there's a large
> difference (typical street motors will get more than 5% leakdown), you
> divide the two observed values and come up with a fraction. That's the
> amount of leakdown. e.g. line pressure 100 PSI, cylinder pressure 98 PSI.
> 98/100=.98 ergo - 2 percent leakdown.
>
> Now here's the nifty part - you listen to the tailpipe, carb throats and
> crankcase and observe the coolant in the radiator and you can tell where
> the presure is leaking to. If you hear it coming from the oil filler cap,
> for example, then the leak is past the rings - similarly, noise from the
> exhaust pipe would indicate a leaky exhaust valve seat or "hung valve".
> Bubbles in the coolant = bad head gasket.
>
> You then follow the leads of your discovery (or more likely discoveries!)
>
> The leakdown test is very valuable for evaluating the condition of an
> engine - I would never go by just the compression. A compression test is
> quick and dirty for evaluating the motor. A leakdown test will likely be
> more revealing.
>
> If you don't want to part with $70 and you don't have a compressor, a
> competent repair shoppe will have the necessary tools to do the test.
> Figure an hour of billable time, maybe a bit more.
>
> Note: when you pressurize the cylinder, you may need an assistant to hold
> the brake pedal down FIRMLY (with the car in gear) or the motor will
> rotate to the bottom of the stroke on the cylinder being tested. READ -
> THE CAR CAN ROLL WITH THIS FORCE. Please exercise caution when performing
> a leakdown test.
>
> > Thanks,
> > Peter
> > '68 TR250
>
> regards,
> rml
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