Leakdown testers

[38racing]

I was surprised to see that there was no thread on these. I just got the PERFORMANCE TOOL W89729 from rockauto. It appears ,based on videos I've watched, to be what harbor freight sells. I had my homemade one but for need of the hoses from it to engine I bought this new one. It works a bit different and not sure if I really like it. My homemade one was more like the OTC 5609.
I'm thinking of either using the hoses from the new one on my homemade or replacing the right hand gauge of the new one with a gauge that just shows the psi. I'm thinking the one on it now only has a 15 -25 range because at setup it goes to max at 15-20 on the left gauge. That may be too low for tracking source of the leak. Thinking maybe at least a 30-60 would be better.

[KE4AVB]

I actually did a partial review of the HFT unit here. I have using it for a while. There is a couple things to watch out for one is when the unit is first connected to the air source that the regulator is set to zero prior to connecting or the unit can peg and damage the percentage gauge. I actually destroyed my first HF unit doing this. The second problem I have noticed recently is the HF unit's regulator tends leak (creep) above the desire pressure setting.

But far as looking leaks even the low pressure works fine for me. Actually it allows modified test on OHV engines. This is where you disable the valve train by removing the push rods and hand turning the engine crankshaft 360 degrees testing for tapered and oval cylinders. I have found several engines that good leak down tests at TDC that were bad near the BDC of the strokes. With 100 psi there is no way I can hand the engine the engines to do this as flywheel would rip out my hands.

On the subject of OHV I have found several 310000 series head gaskets blown using the HF tester.

Now the tester has been sitting since last Fall as I haven't needed to do any test so far this year so it may or not work now. I do have a homemade tester that only has a regulated input gauge that used for several years but I never put .140 oriface in it and the second gauge.

[38racing]

I should apologize that there was indeed another thread from 2018 on leakdown testers.

[Arkie]

I have a OTC leak down tester, do not remember the model but it's really good, lots of adapters and can go up to around 90psi if desired. Think it was around $50 from Amazon.


It has really detected lots of bad valves, head gaskets, rings.

One thing strange to me is I recently had a Briggs Twin OHV that was smoking like a freight train, Blue oil smoke and the leak down tested good (less than 10%) with engine warm and compression good on both cylinders at solid 135.

Ke4avb suggested testing at a lower pressure with the piston off of TDC with push rods removed.

I did such with the engine cold after it had set for couple days and got really bad leak down tests at TDC and all other positions of the pistons. (confirming bad rings)
Appeared that the cylinders/pistons/rings were void of oil after setting couple days tested cold.

[38racing]

update on my experience with the harbor freight type. I was showing 60% leakage but first gauge was like 5 psi so no way to get airflow for hearing any hissing. I replaced the 2nd gauge with a regular 0-90 psi one so I could increase the psi. Now I get hissing but it's at the quick connect, so using this setup is pretty much useless. So I took the hose from a compression gauge and drilled out the plug adapter hole until the schrader valve was destroyed. Now air can pass toward the cylinder. I removed the hose from the HF unit . I plugged the outlet to that hose so that I could calibrate. I found that with no air flow the 2nd gauge reads 2.5 psi lower than the first gauge and this seems to be true from 20 to 50 psi. So if I set psi on 1st gauge to 52.5 I know that with no leakdown 2nd gauge should be 50. Then I put my new hose into the gauge. I threaded it into the sparkplug hole and bring up the psi with the regulator. I can calculate leakdown from 2nd gauge reading. for example I set psi to 42.5 on 1st gauge meaning 40 on 2nd. Test had 2nd at 23. so (40-23)/40 =42.5 % leakdown. I have a thread in technical on that.