at paul anders' page he states that when the vaccum test is performed, vaccum is applied to 20in hg and it should not leak less than <5in hg in one minute. geoff states it should hold 15in hg for 5 minutes. which is correct? either or? i want to cull out the bad ones before i start checking the resistance readings.
k
Full Version: testing a handful of mps units
QUOTE(rhodyguy @ Sep 27 2007, 11:24 AM) 
at paul anders' page he states that when the vaccum test is performed, vaccum is applied to 20in hg and it should not leak less than <5in hg in one minute. geoff states it should hold 15in hg for 5 minutes. which is correct? either or? i want to cull out the bad ones before i start checking the resistance readings.
k
Kevin, check them both ways. It will be interesting to see how the tests shake out. May be similarities and differences.
It will be a study on a group of MPS's!
Gary
i have 5 to test. i'll do both versions and post the results after i get done spraying roundup to beat the rain. i'm hoping the 'pros' will chime in. jeff, geoff, paul?....
k
k
I use the 15in hg for 5 minutes criteria. At 20 in hg it probably shouldnt be too much different...they should not leak in either case. Idle speed intake manifold vacuum is about 15 in hg FWIW....
Having said that, even a leaky MPS will function ok for awhile if the leak down rate is not too severe, the MPS is just on borrowed time until either the diaphragm fractures significantly, or the MPS seals fail to allwo vacuum.
Having said that, even a leaky MPS will function ok for awhile if the leak down rate is not too severe, the MPS is just on borrowed time until either the diaphragm fractures significantly, or the MPS seals fail to allwo vacuum.
It doesn't really matter. All you are doing is testing to see how well the MPS holds a vacuum. 15inHg, 20inHg. Pick one. See how long it holds the vacuum for. Different people have different standards for what is 'good'.
An MPS that leaks down by 5 inHg (from say 15 to 10 inHg) in one minute, will still perform just fine in a car. Even if it leaks down that much in 15 or 20 seconds will probably still perform just fine. My guess is that less than 15 seconds to lose 5 inHg is where it may start affecting performance. But that's just my personal guess.
The main difference between an MPS that leaks down in 30 seconds and the one that leaks down in 30 minutes is that the one that holds vacuum better should last longer. It means that the internal seals are in better condition. Leaks only get worse over time, not better, so the better it holds vacuum, the longer the MPS should last (very generally).
Demick
An MPS that leaks down by 5 inHg (from say 15 to 10 inHg) in one minute, will still perform just fine in a car. Even if it leaks down that much in 15 or 20 seconds will probably still perform just fine. My guess is that less than 15 seconds to lose 5 inHg is where it may start affecting performance. But that's just my personal guess.
The main difference between an MPS that leaks down in 30 seconds and the one that leaks down in 30 minutes is that the one that holds vacuum better should last longer. It means that the internal seals are in better condition. Leaks only get worse over time, not better, so the better it holds vacuum, the longer the MPS should last (very generally).
Demick
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