leakdown
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Joined: Mar 2002
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leakdown
Can anyone tell me the proper procedure and result parameters for a leakdown? Can it be done with a regular compression gauge? I would assume you have to turn the engine by hand to reach TDC of the cylinder so the valves are both closed? Also, any estimates on cost?
My 87 3.2 is using about a quart of Mobil 1 15-50 per 500 miles. I am not comfortable with this, and would like to find out a little about the shape of my engine.
Any help would be greatly appreciated!
Thanks,
Tim
My 87 3.2 is using about a quart of Mobil 1 15-50 per 500 miles. I am not comfortable with this, and would like to find out a little about the shape of my engine.
Any help would be greatly appreciated!
Thanks,
Tim
Technical Specialist
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From: TX
Tim,
You can't use a compression gauge to measure leakdown. You have to pump air into the chamber then measure the retention over a short period of time. Normal parameter is 10% leakdown, or less, is OK. A good mechanic can use the leakdown to diagnose the engine based on listening where the air is escaping. Before having a leakdown test done, you may want to run a bottle of Techron through to ensure everything's as clean as possible.
You can't use a compression gauge to measure leakdown. You have to pump air into the chamber then measure the retention over a short period of time. Normal parameter is 10% leakdown, or less, is OK. A good mechanic can use the leakdown to diagnose the engine based on listening where the air is escaping. Before having a leakdown test done, you may want to run a bottle of Techron through to ensure everything's as clean as possible.
Race Car
Joined: Jun 2001
Posts: 3,706
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From: Virginia Beach, Va.
Yes! Good one Bill, run a bottle of Techron through your motor before a leakdown...loose carbon chips tend to get in the way of the valve seat and gives you inaccurate readings.
You ask: How do these carbon chips come loose?
Answer: When you remove the spark plugs.
Another tip is to ensure you rotate the engine by hand a few times before taking your measurements, this will do a fair job of knocking anything out of the way.
If your mechanic hears air escaping through the oil filler neck, you have some piston ring wear evident, if through the intake, your intake valves/guides may be worn, if through the exhaust...you get the idea.
Expect to pay an hour or two labor at your local P-Car facility...make sure the person performing the test is both familiar with the 911 motor and the procedure!!
A quart of Mobil One every 500 miles? That wouldn't concern me, but then most of mine probably LEAKS out! <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" />
You ask: How do these carbon chips come loose?
Answer: When you remove the spark plugs.
Another tip is to ensure you rotate the engine by hand a few times before taking your measurements, this will do a fair job of knocking anything out of the way.
If your mechanic hears air escaping through the oil filler neck, you have some piston ring wear evident, if through the intake, your intake valves/guides may be worn, if through the exhaust...you get the idea.
Expect to pay an hour or two labor at your local P-Car facility...make sure the person performing the test is both familiar with the 911 motor and the procedure!!
A quart of Mobil One every 500 miles? That wouldn't concern me, but then most of mine probably LEAKS out! <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" />
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From: TX
[quote]<strong>A quart of Mobil One every 500 miles? That wouldn't concern me, but then most of mine probably LEAKS out! </strong><hr></blockquote>
Actually, running at the track does make an impact on 964 oil usage, at least on mine (as opposed to my 911SC which just seemed never to use oil, track or no track).
On the leakdown, one other thing is that is should be done on a warm engine for best results.
Actually, running at the track does make an impact on 964 oil usage, at least on mine (as opposed to my 911SC which just seemed never to use oil, track or no track).
On the leakdown, one other thing is that is should be done on a warm engine for best results.
