Does the motor have to be hot to get accurate results with a leakdown?
12-10-2003, 11:09 PM
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Does the motor have to be hot to get accurate results with a leakdown? If it does how in the hell do you keep from burning your hands on the headers?
Also how much psi do you inject into the cylinder?
Also how much psi do you inject into the cylinder?
12-10-2003, 11:27 PM
#2
The results will be most accurate if the motor is hot/warm. I think the mechanix gloves help a lot with the avoiding getting burned part.
Had a leak down done on engine that was going to go into my 91 RS. Since the engine wasn't in a car, the leak down was done cold. Most cylinders were ~10 percent but one was 42 percent and the adjacent one was 35 percent. The 10 percent was good for being cold. The 42 & 35 were pretty bad no matter how you look at it.
Had a leak down done on engine that was going to go into my 91 RS. Since the engine wasn't in a car, the leak down was done cold. Most cylinders were ~10 percent but one was 42 percent and the adjacent one was 35 percent. The 10 percent was good for being cold. The 42 & 35 were pretty bad no matter how you look at it.
12-11-2003, 08:50 AM
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I used 100 psi when I did my leak down. Put about 20 psi in the cylinder and then turned the crank to TDC for a given cylinder. With more pressure you can't turn the crank. Once you get the piston to the top it will stay when you pressure up. You will know it TDC by rocking it back and forth slowly until you feel no resistance to the pressure.
12-21-2003, 04:01 PM
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I just ordered the leakdown tester. I think I am gonna do it cold and look for anything that stands out like you did 99 black TA, I am also gonna do the 20 psi rotate the crank thing like Larry said to find TDC.
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12-21-2003, 11:38 PM
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So lets say I set my tank for 100 psi, I then have to set the regulator on the leakdown to let 100 psi through? After that how do I determine the % leakdown? What do you mean by set it to 0?
12-22-2003, 07:09 AM
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Mike,
The leak down tester comes with an inline orifice. The orifice is located just before going into the cylinder and before the cylinder pressure gauge. The normal recommended orifice for our engines is .040 diameter. You have a inlet supply pressure gauge, an orifice and then a gauge down stream of the orifice. With leakage in the cylinder via the valves, rings or head gasket the cylinder pressure will drop as the .040 orifice cannot supply the cylinder at a rate fast enough to hold the pressure the same as the inlet pressure. Depending on how fast the pressure drops in the cylinder determines the rate of leak down.
If you use 100 psi it simply makes the percentages easy to read without calculations. If your tank pressure is 100 and your cylinder pressure reads 95 then you have a 5% leak down. Supposedly anything less than 10% is suppose to be ok. When I ran mine no cylinder had less than 4%. I ground my valves myself so I may have done better then standard factory valve grinding.
Hope this makes sense.
The leak down tester comes with an inline orifice. The orifice is located just before going into the cylinder and before the cylinder pressure gauge. The normal recommended orifice for our engines is .040 diameter. You have a inlet supply pressure gauge, an orifice and then a gauge down stream of the orifice. With leakage in the cylinder via the valves, rings or head gasket the cylinder pressure will drop as the .040 orifice cannot supply the cylinder at a rate fast enough to hold the pressure the same as the inlet pressure. Depending on how fast the pressure drops in the cylinder determines the rate of leak down.
If you use 100 psi it simply makes the percentages easy to read without calculations. If your tank pressure is 100 and your cylinder pressure reads 95 then you have a 5% leak down. Supposedly anything less than 10% is suppose to be ok. When I ran mine no cylinder had less than 4%. I ground my valves myself so I may have done better then standard factory valve grinding.
Hope this makes sense.
12-22-2003, 11:09 AM
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If you bought a professional leak down kit it surely should include the orifice. I made mine by drilling a 1/4" socket head allen plug and threading it into a 3/8 NPT pipe.
12-22-2003, 10:57 PM
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again thanks for all of the tips guys, Ill post the results once I am done. I prob wont get the tester until near new years considering the holidays and everything but maybe I'll get lucky and by some miracle it will be here before xmas.
12-25-2003, 12:11 AM
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Originally Posted by Mike K.
again thanks for all of the tips guys, Ill post the results once I am done. I prob wont get the tester until near new years considering the holidays and everything but maybe I'll get lucky and by some miracle it will be here before xmas.
I'm making one. It is super easy and the parts are cheap and easy to source.
Compression tester $20
Regulator with gauge- $10
1/4 NPT T + a few other quick connect fittings... 5$
So for about 35$ you have a compression tester and a leak down tester. You can use the compression gauge as the secondary gauge after the orifice.
The orifice can be made by taking the 1/4 coupler filling it with epoxy and then drilling the correct sized hole.
