Leakdown test question

Birdie2000

Birdie2000

Club Member
Could someone walk me through how to do a leakdown test on an engine?

I just did one to an engine sitting on a stand and something seems off. The numbers were great, almost too great. Something about the tester I have seems weird though. It's a two-gauge model and it says to turn the knob until the 2nd gauge reads 0% leakage and then take a reading. Well, you have to wait a minute or two for it to move, but often times it was 1-2% and absolutely no higher than 4% on any cylinder. Now the thing is, when I set that second gauge to 0% per the tool's instructions, it was only introducing maybe 13-15psi into the cylinder. Does this sound right? I would think you would need 100psi+ to be more accurate since an engine sees such high cylinder pressures.

Any insight?
 
it won't check well at 100psi if the engine has not had the rings run in and seated. go with it. sounds good to me.
 
What do you mean by run in and seated? Do you mean not warmed up or are you thinking of a fresh build? The engine is used and has some miles on it.
 
388Monte said:
You need to leak the motor down warm
Click to expand...

Unfortunately that's not an option. It's been out of the car for a while, and in an effort to have the car ready for the Dream Cruise the engine is already torn down to a short block. Obviously it's too late to do anything else than just put the new top end on it and hope for the best on the short block, but I would just like to know for future reference.
 
even with horrific leakdown it'l be fine. what rings do dynamically vs statically is a huge world of difference. I once saw a 9.50 all motor car go from a 4% leakdown to a 28% leakdown and it never slowed down. It did smoke a touch but that was it.
 
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