I recently acquired another 'teener. See video here.

I have a leakdown tester like the one pictured below. The included instructions are pretty worthless. There is a hose extension that screws into the spark plug hole in the head. The other end connects to the gauge. My question is, do I add air from my compressor and use the regulator on the tool to set the leakdown gauge (on the right) to 0% and then connect it to the piece of hose, or do I assembly everything together and then add air?

I tried the latter method and used the regulator to adjust the leakdown gauge to 0% and then it never went down.


Click to view attachment

Make sure the cylinder you are testing is at TDC compression stroke. Screw the hose into the spark plug hole. Attach to the hose on the tester. Connect the inlet to your compressor hose, then dial in 100psi on the high side gauge. The difference between 100 and the reading on the second gauge is the percent of leakdown. At inlet pressures below 100psi you have to do a little math to derive the %.

That's the $39.00 setup from Harbor Freight.

Ensure the engine is warm and test each cylinder at TDC..

Oh, make sure the crank can't rotate while you have the cylinder pressurized.
and note where the air leaks from, through the crankcase or intake or exhaust valve.

The leak down tester that you have, if it is the HF unit, is next to worthless. I tried two of them, and neither of them would register. When I ponied up and bought a real one, it worked perfectly.

Zach

Imagine that.

Apply that logic to EVERY component that comes into contact with your 914.

I know that the HF stuff is not high quality, or even average quality. I called three local auto parts places and they didn't sell them (one didn't even know what I was talking about ).

I figured that if I bought a good one online for $100-150, I'd still probably end up with one with gauges made in China.

The gauges on my Longacre leakdown tester do not specifically state country of origin, but they are marked USG which is an Ametek trademark. This still doesn't tie down country of origin but Ametek is a US company with an excellent reputation. The pressure regulator is Parker and does indicate 'Made in Mexico.'

The problem is not China, although given my druthers I prefer to avoid them too. The problem with China is that they will sell whatever you are willing to pay for, which makes it not so much a China problem as a 'purveyor of cheap goods contracting production in China' problem. Face it - they have the technology to make ultra-high quality electronics and aircraft/spacecraft-rated stuff. If that's what you contract and pay for, you can get it.

The problem is that lots of companies pay to have cheap, low-quality goods manufactured - it's a real buyer-beware environment.

You can buy a $50 drill press or a $500 drill press and you can get what you pay for; just don't be expecting a $500 tool for $50.

Amen brother!

Quick update: I noticed that the leakdown gauge was getting pegged (0% leakdown) when I had only 15 psi into the cylinder. So I replaced the leakdown gauge with a regular 100 psi gauge. I tested the gauge by putting 100 psi to the gauge and both needles swept to max together.

So I warmed up the motor, connected the gauge, added 100 psi to the cylinder
and the leakdown gauge read 97 psi. The other three cylinders read 97, 96,
and 95. Now I know that's not a race motor sitting in there, so I think I'm
still without useful data on this motor.

Maybe the PO before the guy I
bought it from had just rebuilt the motor and it's got no miles on it.

Are you sure it said 97 PSI? The leak down dial is a percentage, as in 97% leak (goal being under 20%).
In general, 0 = no leak at all. 100 means there is no seal at all. If you really have leak numbers in the high 90s, and the gauge is not broken, then there are issues.
I have to think that the gauge is wrong, as I don't even thing the engine would run with that high amount of leak...

If the leak gauge is reading 97 PSI, that tells you nothing.

Zach

The leakdown gauge has a range from 0 to 100 psi gauge. It read 97 psi, so with 100 psi on the left gauge, that would be a 3% leakdown. It's my understanding that 3% leakdown is extremely low, something you'd find in a race motor.

Neither of the HF units I had worked that way, but it is possible they changed.

Zach

What he said is that he replaced the % leakdown gauge with a regular 100 psi gauge.

So 100 in, 97 left = 3% leak down ... damn good number.

Is 3% to 5% realistic on a '74 2.0 of unknown condition?

yes - because it is unknown.

OTOH, now that you have ~4% it is no longer unknown, and therefore suspect

Seriously - it is but ONE bit of information.

The compression-gauge number is another data point. An engine can have excellent leakdown but bad compression and still be undesirable as a street engine. (One possibility being a high-overlap race cam.)

An engine can have good leakdown and -still- need a rebuild if the cam is flat because the lifters went bad.

Or - you could have good leakdown because the rings are rusted in place :-) We'll assume that't not the case.

(Call it) 4% is good. Take your miracles one at a time and be happy.

Put it this way - you're either going to tear the engine down or you're not. I think you'd be silly to tear down a 2,0 914 engine without running it first but be aware there is an argument to be made that the only appropriate thing to be done is tear it down and be sure. That course of action is more work and money, but it does not risk as many broken parts.

You roll the dice and live with the consequences.

Geeze, how did I miss that part.

My bad.