Åudios69

What is the difference between the two?

QCRAZY

A leak down test checks how long it will hold compression. So with a leak down test you measure the compression (non-mechanical) and then see how fast it "leaks down"!!

There testing "similar" things just slightly different ways!! I'm sure others can tell you why one is better in certian situations!!

VAP

on nominal specs laid down by Audi via Bentley. Leak-down is done without cranking the car and based upon air forced into the sparkplug hole and how fast each cylinder while at TDC loses it's pressure or "leaks down." Compression tests are quick/cheap and a guide for measuring approximate life remaining on an engine while leak-down is usually used to diagnose a symptom, ie; cracked/broken oil/compression ring or bent/burned valve. With a leakdown you can usually diagnose if it's a ring by listening thru the oil filler cap or the dipstick tube. If its a exhaust valve you can listen into the exhaust pipe and conversely if an intake valve, thru the TB or intake tract. While intake valves seldom burn and hardly bend as it's the larger diameter exhaust that that nudges a piston or burns you're usually stuck with a burned/bent exh valve or a broken piston ring if the car fails.

HTH

Åudios69

Tester?? is it like a vacuum/pressure unit? How much?

Thanks!

VAP

My Snap-on runs $280 and Matco sells a nice one for just under $200. But any good automotive tool shop or even NAPA can get them for you. Just stick with dual gauge (important) and American made rather than imported save for the W. German Hazlet... (best I've ever seen) but over $500 and you'll be fine.

Åudios69

thanks again!