911newbie

Please excuse me ingorance, but I am new to this. I keep hearing about the importance of having a leakdown test done on any car that I am interested in buying. Several people said that it can detect valve guide wear. How is this possible. If the pressurized cylinder is losing compession how can you tell where it is losing pressure. Rings. valves, seats, or guides? In case it helps I an only talking about 3.2L cars.

Steve Weiner-Rennsport Systems

Hi:

A leakdown test will only give an indication of ring and cylinder wear, and degree of valve leakage. It will not tell you anything about worn guides or broken rings.

When each cylinder is pressurized with air, the percentage of air passing by the rings & valves is displayed on the instruments guage. Observing where the air is leaking from gives an indication of where the trouble (if any) might lie.

Note that:

Air leaking from the air cleaner opening is leaky intake valves.

Air leaking from the exhaust pipe is leaky exhaust valves.

Air leaking from the oil filler tube indicates worn rings and/or cylinders.

Leakdown testing done by experienced and competant personnel is a valuable and indispensible diagnostic tool.