What holds the crank ina leakdown test?

[svx_commuter]

I got a question

When a leakdown test is done how high is the pressure in the cylinder?

What holds the crank in the TDC position for this test?

Here is a discription of the test

http://www.geocities.com/dsmgrrrl/FA...own.htm#WhyGet

Thanks,

John

[Trevor]

Originally Posted by svx_commuter

I got a question

When a leakdown test is done how high is the pressure in the cylinder?

What holds the crank in the TDC position for this test?

Here is a discription of the test

http://www.geocities.com/dsmgrrrl/FA...own.htm#WhyGet

Thanks,

John

(1) Interesting and very pertinent. Surely will be dependent on what is available from a normal shop compressor.

(2) It would appear that the pressure used is not sufficient to move the piston.

It would seem a good test when used to identify a problem, but should be used in conjunction with a standard compression test, which involves non static factors.

[ItsPeteReally]

When a leakdown test is done how high is the pressure in the cylinder?

The higher the better, the leakage is noisier and easier to find. Lots of garages use 100lb psi, but that's just to make the maths easy when doing the percentages

What holds the crank in the TDC position for this test?

Nothing. If you think about it, when the engine is at top dead centre, you could apply infinite pressure and the piston would not move. In practice, as long as you are within a few degrees of tdc, either way, the rotational force on the crank is very low.