Hi all. Are there any tutorials on how to do an accurate cylinder leak down test? I can find TDC one cylinders 1 and three, what's the best way to find TDC on 2 and 4? Would the distributors rotor position be close enough to ensure the valves are closed? Thanks

I did this for the first time the other night. I saw a youtube vid where the tech rapidly covered/uncovered the open end of the tube until the pressure started to drop - sure, I wish I could gauge the degrees, but this worked for me - even if I went a little too far and had to repeat . . .

Oh yeah - almost forgot -

I did this last night! Yes, #1 & #3 are easier to find using the TDC mark on the fan. With all of my spark plugs out and in 5th gear I was able to locate TDC on #2 & #4 visually with a light, peering into the spark plug hole. The distributor will get you very close and visual back and forth got me there perfectly. Pretty easy too. FYI, warm the engine up BEFORE the leak down testing, and EVERYTHING is easier with the engine cover removed!

However, as I chase down an incredible lean ide and a lean hicup/hesitation leaving stop signs, I was not impressed with my leakdown numbers on 2/4 of the cylinders. I then went ahead and checked the compression of each cylinder, again lower than I'd like to see. I recently adjusted the valves but will pop the covers off and recheck and redo all of my leakdown/compression again to make sure a valve hasn't tightened up.

Have fun, you got this!

Get the leak down tester from HF or a cheapie bone from ebay. Or rent one from your FLAPS.

Set your compressor to 100psi. This will make your life math free.

Hook up the tester and pressurize the cylinder. Now 100 minus whatever the gauge reads is your leak percentage. Easy. Cross reference with your manual for leak tolerance (I can’t remember). Now, while pressurized LISTEN and LOOK for where the air is leaking out. Spray soapy water around the heads and cylinders. Look for the bubbles.

Air leaking into the crank case will come out via the oil filler. That’s an indication that your rings may be tired. Bubbles at the cylinder base indicates register collapse. Bubbles around the valves indicates valve issues. Bubbles at the cylinder to head joint indicates a “head gasket” leak.

Do compression testing first.

Good compression + good leak = strong engine.
Weak compression + weak leak = rebuild.
Strong compression + weak leak = issue, possible rebuild. (Uncommon but happened to me - was register collapse)
Weak compression + good leak = not possible.

Zach