g741.org

Hi all!
I just got a leak down tester.
Looks like it will be a real aid in diagnosis.

http://www.summitracing.com/parts/SUN-5 ... toview=sku

Anybody have any thoughts?
Anybody have any tips/ tricks.
J.B.

Yes it is a very helpful troubleshooting tool. Not always needed but when other symptoms or tests lead to a possible static or dynamic cylinder seal issue they are the perfect tool. They are slowly becoming more popular in the automotive field. They have been very popular for a half century in the piston aircraft engine arena.

From a safety standpoint try to keep in mind the air pressure you are introducing on top of the piston can be quite powerful and can move the crank when you may not want it to move. This is particularly true if applying the air pressure with the piston at TDC. BC should not be an issue. But most tests should be done at the top which is the high wear area and yields a more honest assessment of the cylinder's condition. Be sure to leave the air noise source area open before you start your test. The cap off the oil filler tube or dipstick, air cleaner open and radiator cap off. Exhaust should not be blocked.



Looks like your new tester has direct pressure reading gages so you will have to compute the percentage of loss for your tests. But the instructions that come with it will explain that.

There are several good web sites that offer lots of tips and ideas. Just google cylinder leakage test limits. This new tool along with a vacuum gage and compression tester will take you a long way to resolving any issues that may arise with cylinder/engine performance.

I just had a brain fart.
You could make a really simple tester out of an old spark plug and
an air hose.
Break the guts out of a spark plug, adapt it somehow to an air hose.
Put (for example) #1 @ TDC, screw the spark/ air adapter in. Open the air filter and the radiator cap.
Pump er up. Listen at the exhaust and the intake, look for bubbles in the radiator. Voila! Diagnosis tool for where the leak is.
What think the bretheren?
J.B.

J B,

You can buy a fitting that has spark plug threads on one end and threads for an air hose fitting on the other. It can be used for changing valve springs or valve seals, by using the air pressure to hold the valves up while you work on them. With just the fitting though you would only hear where air was escaping,not how much or how long it would take.

FWIW and to prevent turmoil, I used this procedure on a Chevy PU truck

Neat! I just learned another trick! Won't work real good with flatheads, but OHV setups just became a lot easier!

Lifer,
You can hold a flathead's valves closed with air pressure.

Be sure to include a pressure regulator and/or shutoff valve close to the spark plug hose so you can turn it on/off and adjust the pressure without running back and forth to your compressor.

Most leak down testers have a calibrated orifice between the two pressure gages in the .040 to .060 range depending the cubic inch displacement of the engines being tested.