This is topic Leak down test results, what exactly do they mean? in forum Tech Talk at Northern California Ford Owners  .


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Posted by 166 Merlot (Member # 1549) on :
 
Wussup Cafords! My engine has 130 and has been boosted for the past 10k. 3rd set of head gaskets currently. still not 100% tuned. most of the air ended up coming out of the valve cover breather and throttle body. Oh yea and I performed the test on a cold engine. how would this affect my results?

Cylinders:

4-40% 8-40%
3-20% 7-20%
2-25% 6-25%
1-20% 5-20%
 
Posted by JohnB (Member # 969) on :
 
Did you rotate the engine over to BTDC for each test?? It doesn't look like it...
 
Posted by Mean2001GT (Member # 1750) on :
 
with all the head gaskets i'd be concerned if any bubbles were coming out of the radiator during the leak down. but if it's coming out of the breather it means you have blow-by. which is what is supposed to happen, especially when the engine is cold. but 40% is too high. 15%-25% is pretty average.

are you chasing a problem? or just testing? another test you may want to consider is a "running compression" test.
 
Posted by 166 Merlot (Member # 1549) on :
 
yea i matched up the rotor to the corresponding plug wire to do the test. No bubbles from the radiator [Smile]

I'm kinda chasing a problem, kinda just curious to see. haven't done a running compression test, what the difference between that and a regular compression test? I might have to look into that.
 
Posted by hidnn.o.s. (Member # 1219) on :
 
From what I've seen, good leakdown numbers are BELOW 10%

Goodluck with that [Frown]
 
Posted by 88DroptopGT (Member # 2535) on :
 
Repeat the test with the engine at operating temperature since this is when you actually drive the car. The readings should be somewhat less then we are getting in reasonable territory.
 
Posted by hidnn.o.s. (Member # 1219) on :
 
Warm leakdown numbers should definitely be UNDER 10%
 




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