How do I use this leak down tester?

[Batoutahell]

I'm not convinced the instructions are correct. Here is my tester from Harbor Freight.

According to the diagrams, the pressure gauge is on the left and the leakage gauge is on the right.

The instructions:
1. bring engine up the temp (ok)
2. remove spark plugs and disable fuel delivery (ok)
3. position piston at tdc (ok)
4. set air compressor between 7-100psi (ok, set about 50psi)
5. connect tester to air compressor hose (ok)
6. screw adapter hose into cyl. #1 (ok)
7. connect adapter hose to the tester (ok)
8. turn regulator knob on tester until its gauge reads zero at the end of the yellow band (this step confuses me?)
9. you can now read the amount of leakage on the leakage gauge as a % loss

Regarding step 8, there is no "yellow band" on the pressure gauge. There is a yellow band on the leakage gauge. Is this a mis-print in the instructions?

If I turn the regulator knob on the tester to zero out the pressure gauge as in step 8, the dial on the leakage gauge shoots up to 80-85% (in the red) like in the pic above. I've tried this on 2 cylinders so far with similar results.

How do I operate this leak down tester?

 

[Daedalus]

Yeah, not what I recall from shop. With the cylinder-side hose disconnected from the quick-connect, no air will flow out of the tester, and the leak-down should read 0%. If you hook up the cylinder-side hose but leave it un-installed in the plug hole, the air should be free to flow out, and the tester should read 100%. I think this is the calibration that's required--adjusting the knob with the air free-flowing until the tester reads 100%. Then hook it up to the cylinder and it should give you a good reading.

 

[NCC-1701D]

These are the steps for my Snap On cylinder leakdown tester


1) run the engine until it reaches normal operating temperature
2) remove all spark plugs
3) remove the air cleaner, oil filler cap, engine oil dipstick and radiator cap. Open the throttle all the way
4) position the piston in the cylinder ot be tested at Top Dead Center of the compression stroke. Always rotate the wngine in the same direction as the when engine is running

5) compare the thread length of the adapter to be used to the thread length of the spark plug. make sure that threads of the adapter do not prtrude into the cylinder any farther than the spark plug. this could cause damage to the pistons or valves
6) thread the adapter into the spark plug hol. tighten hand tight only
7) be sure the regulator knob is turned all the way counter clockwise before connecting the tester to air pressure
8) connect the tester to the air supply (120-200psi)
9) connect the tester to the adapter
10) turn the regulator knob clockwise to adjust the air pressure to 100psi on the tester pressure gauge.


read and record the precentage of cylinder leakage shown on the percentage gauge. listen and note any air escaping from the intake, exhaust, crankcase or adjacent cylinders. also in look in the radiator for air bubbles. this information will be used for diagnosis.

reduce the regulator pressure to 70psi before disconnecting the adapter.

 

[Larry Bastanza]

1. bring engine up the temp (ok)
2. remove spark plugs and disable fuel delivery (ok)
3. position piston at tdc (ok)
4. set air compressor between 7-100psi (ok, set about 50psi)
5. connect tester to air compressor hose (ok)
7. connect adapter hose to the tester (ok)
8. turn regulator knob on tester until its gauge reads zero at the end of the yellow band (this step confuses me?)
6. screw adapter hose into cyl. #1 (ok)
9. you can now read the amount of leakage on the leakage gauge as a % loss

I think this is the sequence you need to follow.

BTW, 50 PSI is not really high enough IMO, I typically use 100psi.

HTH,
LarryB

 

[4mulacar]

1. bring engine up the temp (ok)
2. remove spark plugs and disable fuel delivery (ok)
3. position piston at tdc (ok)
4. set air compressor between 7-100psi (ok, set about 50psi)
5. connect tester to air compressor hose (ok)
7. connect adapter hose to the tester (ok)
8. turn regulator knob on tester until its gauge reads zero at the end of the yellow band (this step confuses me?)
6. screw adapter hose into cyl. #1 (ok)
9. you can now read the amount of leakage on the leakage gauge as a % loss

I think this is the sequence you need to follow.

BTW, 50 PSI is not really high enough IMO, I typically use 100psi.

HTH,
LarryB

Larry is correct set the gauge to 100 psi to make the reading a simple measurement of percentage (100psi= 100%). This setup is confusing fromthe way it was designed I typically have both guages which are the same however this unit is asking you to adjust the regulator unitl you see 0% at the end of the yellow area which is actually 100% if the guages were the same.
The first gauge reads the system pressure and the second guage reads the leakage coming from the engine, if you hear air escaping from the air intake then you have intake valve leakage and conversely if you hear air escaping from the exhaust side then it is from the exhaust valve. I would swap out the second gauge for one indentical to the first gauge(one reading system pressure) to make this more intuitive that second gauges marking takes a simple tool and makes it confusing to look at and read.

 

[NSX-Files]

How hard is it to get each cylinder at TDC? Are there markings that are easily visible with the engine in the car?

 

[Batoutahell]

Using NCC-1701D's method: as I begin step 10 and turn the regulator knob so the air pressure on the left dial increases, the right dial spikes. I can't even get up to 20psi on the left gauge before the right gauge spikes (clockwise) off the scale.

Larry's method doesn't seem to work on my tester, either. Air comes rushing out of the adapter hose while I set the right gauge to "zero." As I screw the adapter hose into the cylinder, the right gauge spikes clockwise off the scale. I'm using 100psi output at the air compressor.

When I hook the tester up to 100psi at my compressor, I should be able to adjust the regulator knob such that the left gauge reads 100psi (to make things simple) while the right gauge should read zero (showing 0% leak). Right? Once calibrated, when I hook the tester up to the adapter hose in the cylinder, the left gauge should stay on 100psi, and the right gauge should swing counter-clockwise to show the % leak. Right?

Maybe one or both of the gauges is broken. The right gauge in particular has spiked off the scale a couple of times as I've been trying to figure out how it works.

 

[4mulacar]

You are correct something is wrong, I will take a picture of mine on Monday as its getting to late tonight. Your unit does appear stange to me, I built mine and on the top side of the regulator to set system pressure I placed a guage, then from the center I placed a reducing bushing to reduce the air flow(we do not need the same volume we are filling a small combustion chamber) then I placed a gauge block tee with a guage in the center position and on the end a thumbscrew valve to let the air flow to the flexible hose going to the combustion chamber and you can now read the second guage to view leak down. I will get the pictures done when I arrive from work on Monday and you should be able to work through this. You can PM me also to assist you with this.

 

[Daedalus]

What happens if you first calibrate it to 100% before screwing in the adapter? 100psi is a convenient value to use for a single-gauge tester but it is not necessarily the pressure to use with a dual-gauge tester. The value is irrelevant and depends on the size of the internal orifice. Calibrating means finding a working pressure that shows 100% leakage under free-flow.

 

[4mulacar]

I'm not sure I get your meaning here, I also have never tried using a single guage this would make it tough to make a reading. The system pressure is your input when you see my post later this evening it will become very clear, this is not rocket science or I would not have been able to produce a unit. I have used this method for over 20 years and learned this from my engine builder at the time Jay Ivey of Ivery Racing engines a formula ford engine wizard.

 

[4mulacar]

Batoutahell, here is a picture of my home made tester. Hopefully you can follow my previous posting information to see how pressure is developed and flows through the test unit. The idea here is to get a pressure differential from the system to the combustion chamber which is the unit under test. Regulated pressure flows through the metering block (regulator) and then out the outlet to the second gauge block tee. Then when the thumbscrew is turned parallel to the ground air flows to the combustion chamber and the difference is read on the second gauge. The first gauge will allways be steady (regulated). The second gauge will read the difference between the gauges and give you the indication of whether the chamber is holding pressure or leaking and where its leaking (carb or air intake) intake valve, exhaust side exhaust valve and finally out the breather rings. PM if you want to build this unit it is very inexpensive.

 

[4mulacar]

NSX-files, sorry I forgot to answer your post, TDC can be a tough determination. I just got my NSX and have not yet started to play with tuning it as of YET. There are numerous tools out there from wistling tools to a simple dial indicator screwed into the spark plug hole. I would tend to believe these smart engineers for our cars placed a timing mark on the harmonic balancer and an indicator on the block (old school chevorlet) however I cannot say what is on our engines as I have not looked. Call one of the tuning shops I'm sure they know, it could even be indexed on the cam gears but there still is probably a reference on the engine pulley.

 

[Larry Bastanza]

NSX-files, sorry I forgot to answer your post, TDC can be a tough determination. I just got my NSX and have not yet started to play with tuning it as of YET. There are numerous tools out there from wistling tools to a simple dial indicator screwed into the spark plug hole. I would tend to believe these smart engineers for our cars placed a timing mark on the harmonic balancer and an indicator on the block (old school chevorlet) however I cannot say what is on our engines as I have not looked. Call one of the tuning shops I'm sure they know, it could even be indexed on the cam gears but there still is probably a reference on the engine pulley.

Front intake cam gear. The crack only has #1 TDC.

LarryB

 

[4mulacar]

Great Larry thanks you are one of the reasons this is a great forum along with the builder of this forum, my hat is off to you guys!By the way Larry I'm a Snap on addict also primarily do to the fact these tools do not mar the aircraft hardware I use exclusively on my race car something I learned from the illustrious Carrol Smith whose siminars I attended every time he either came to my state or I was someplace near to where he was speaking, he taught many of us race car engineering the man was a wealth of information and his methodology I live my racing activities by. For those of you who do not know who this great auto racing engineer was, google him and buy his books his knowledge was meant to be passed on and may God rest his worthy soul!