Need a quick answer..

Compression measures cranking pressure. Leakdown measures if you have any leaks in your chamber.

Now here's my question. If my compression numbers are okay, does that mean that my leakdown numbers will be okay too? If not, then why not?

The reason I ask is because I was told that if my compression numbers are fine, then i woudnl't have to do a leakdown test will be okay too.

 

compression tells you if you have a leak

leakdown tells you where the leak is

 

leakdown measures the pressure loss in the cylinder and can help tell you WHERE the leak is occuring. compression tests just show the compression when cranking the motor. correct me if Im wrong.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DragII &raquo;</TD></TR><TR><TD CLASS="quote">compression tells you if you have a leak

leakdown tells you where the leak is</TD></TR></TABLE>

then why do some people have perfect compression but their leakdown results sux ***??

Is it because you can have compression that's like 250,250,250,250 and have a leakdown of 10%+ in all four cylinders?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr.Integra &raquo;</TD></TR><TR><TD CLASS="quote">

then why do some people have perfect compression but their leakdown results sux ***??

Is it because you can have compression that's like 250,250,250,250 and have a leakdown of 10%+ in all four cylinders?</TD></TR></TABLE>

that would be fine then. Nothing wrong with that. I forget the OEM tolerance but there will be some loss. Leakdown will not show 0% loss. compression is something that happens when the piston moves to TDC. if you do a compression test, leave the gauge in the spark plug hole, and let it sit, you will lose (leak) pressure from the cylinder. they arent air tight, but they happen so fast that the air doesnt have to leak out when on compression stroke.

 

I was a bit too general I guess....here's a decent write up http://www.vclassics.com/archive/leakdown.htm

if compression test #s are high across the board, I wouldn't feel the need to leakdown test it.