Snap-on Leak Down Tester - Dual Gauge

Mark Yacavone · 10-23-2015, 11:22 PM

Bruce, I don't don't think those regulator type gauges work real accurately with little or no air going through them.
Try loosening up the plug till it reads and then back it back down..
You probably have about 2 % :-)

Ed Wright · 10-24-2015, 08:53 AM

I still have an old Sun percentage of leakage tester, one gauge. I have never seen one of those cheaper two gauge units I thought was correct. No two appear to give the same numbers. Usually low. I have seen 2% on those when you can hear air out of the crank case breather. My Sun would show 6% to 8% on the same cylinder. Only thing that would show 2% on mine would be some Total Seal gapless rings. Also had one built into one of my big Sun engine Analyzers, both read the same. Be worth it if you could find one.

Bruce Noland · 10-24-2015, 12:46 PM

I have had this unit for several years and just got around to using it the other day. I don't think it was cheap. After calls to several different Snap-on numbers and 18 prompts later I did get some info. Nothing really new, there is a .040 orifice that meters the air from the pressure side. The air passes by the leak down gauge and then to the spark plug hole. Once the cylinder is full, the leak down gauge can read the pressure. So according to these folks you can get close to a zero leakage with a .019 top ring gap. Also, I made the mistake of not using the long thread adaptor. So live and learn.

Alan Roehrich · 10-24-2015, 12:59 PM

The best I've seen with my stuff is around 4% or so. Knowing how little blow by there is on the dyno, I'm okay with that. A leak down test is a diagnostic test to locate a problem if something is wrong. Given that it is a static test, you're just finding where the leak is, and what the likely component is. I only leak an engine to see what is wrong with it in most cases. I suppose you could leak an engine fresh off the dyno, establish a baseline, then use that to see what the ring seal is after a given number of passes. The problem is accurately duplicating the conditions.

Mark Yacavone · 10-24-2015, 02:46 PM

Actually meant to say to loosen the hose in the plug hole, just to see a reading.
Suggestion still applies.

10-23-2015, 11:22 PM	#1
Mark Yacavone Veteran Member Join Date: Mar 2002 Location: Miles From Nowhere Posts: 7,815 Likes: 2,904 Liked 5,121 Times in 1,952 Posts	Re: Snap-on Leak Down Tester - Dual Gauge Bruce, I don't don't think those regulator type gauges work real accurately with little or no air going through them. Try loosening up the plug till it reads and then back it back down.. You probably have about 2 % :-) __________________ "We are lucky we don't get as much Government as we pay for." Will Rogers

10-24-2015, 08:53 AM	#2
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 390 Times in 170 Posts	Re: Snap-on Leak Down Tester - Dual Gauge I still have an old Sun percentage of leakage tester, one gauge. I have never seen one of those cheaper two gauge units I thought was correct. No two appear to give the same numbers. Usually low. I have seen 2% on those when you can hear air out of the crank case breather. My Sun would show 6% to 8% on the same cylinder. Only thing that would show 2% on mine would be some Total Seal gapless rings. Also had one built into one of my big Sun engine Analyzers, both read the same. Be worth it if you could find one. __________________ Ed Wright 4156 SS/JA

10-24-2015, 12:46 PM	#3
Bruce Noland VIP Member Join Date: Jun 2002 Posts: 1,855 Likes: 83 Liked 444 Times in 145 Posts	Re: Snap-on Leak Down Tester - Dual Gauge I have had this unit for several years and just got around to using it the other day. I don't think it was cheap. After calls to several different Snap-on numbers and 18 prompts later I did get some info. Nothing really new, there is a .040 orifice that meters the air from the pressure side. The air passes by the leak down gauge and then to the spark plug hole. Once the cylinder is full, the leak down gauge can read the pressure. So according to these folks you can get close to a zero leakage with a .019 top ring gap. Also, I made the mistake of not using the long thread adaptor. So live and learn. __________________ Bruce Noland 1788 STK

10-24-2015, 12:59 PM	#4
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,113 Likes: 1,571 Liked 1,826 Times in 414 Posts	Re: Snap-on Leak Down Tester - Dual Gauge The best I've seen with my stuff is around 4% or so. Knowing how little blow by there is on the dyno, I'm okay with that. A leak down test is a diagnostic test to locate a problem if something is wrong. Given that it is a static test, you're just finding where the leak is, and what the likely component is. I only leak an engine to see what is wrong with it in most cases. I suppose you could leak an engine fresh off the dyno, establish a baseline, then use that to see what the ring seal is after a given number of passes. The problem is accurately duplicating the conditions. __________________ Alan Roehrich 212A G/S

10-24-2015, 02:46 PM	#5
Mark Yacavone Veteran Member Join Date: Mar 2002 Location: Miles From Nowhere Posts: 7,815 Likes: 2,904 Liked 5,121 Times in 1,952 Posts	Re: Snap-on Leak Down Tester - Dual Gauge Actually meant to say to loosen the hose in the plug hole, just to see a reading. Suggestion still applies. __________________ "We are lucky we don't get as much Government as we pay for." Will Rogers