4.0 Opinion about Leak-Down Test results

[mmmkay325]

My 93 XJ 4.0 seems just to be worn out so I just got my hands on a Leak-Down tester...and I want to get some opinions on the results

Cyl.1) 20% leak coming from oil dipstick

Cyl.2) 50% leak coming from exhaust

Cyl.3) 55% leak coming from intake

Cyl.4) 25% leak coming from oil dipstick

Cyl.5) 25% leak coming from oil dipstick

Cyl.6) 30% leak coming from oil dipstick

Miles are unknown on the motor (it was a swap into my yj) and i feel likes like it's lacking power. Money's tight so I'm trying to decide on a swap or rebuild/stroker. I originally thought my rings were done....but now it looks more like a exhaust/intake valve issue or head gasket?? How severe are these results and what are they translating into as far as how bad my motor is???

 

[a_kelley]

'scuse me for a question or two--

percent of what?
is it not on 2&3 that its like 20%-30% and 30%-20% on valves?

PSI compression would tell you better I think, I'm not understanding the percentages..

How's your oil pressure/main bearings? Seems pretty common for the mains+rods to loosen up and egg the cylinders, so just a rering probably wouldn't last long.. My 93 has 23x,xxx on it and it has worn rods+mains, 15 psi low on 2cyl, but still runs.. and has some blowby..

my $.02, compensated for inflation, you get $.20

 

[mmmkay325]

it's % of leak each cylinder has....all cylinders have some leak. How much and where it's leaking from usually determines the health of valves, rings and other things. So i've been told...i'm new to the motor stuff so i was trying to get help of others that may know.

i'm reading the gauge on the leak down tester to give me those % numbers

I original did a compression test and the results were low...which led me to believe the rings were bad...but I've read the leak down test gives you more info so i've done that but I know really know what it's tell me

Oil pressure does appear to be oil...40psi at best but will deep below that when running down the hwy.

I appreciate your .20....i'll take what i can get

 

[a_kelley]

it's % of leak each cylinder has....all cylinders have some leak. How much and where it's leaking from usually determines the health of valves, rings and other things. So i've been told...i'm new to the motor stuff so i was trying to get help of others that may know.
i'm reading the gauge on the leak down tester to give me those % numbers
I original did a compression test and the results were low...which led me to believe the rings were bad...but I've read the leak down test gives you more info so i've done that but I know really know what it's tell me
Oil pressure does appear to be oil...40psi at best but will deep below that when running down the hwy.
I appreciate your .20....i'll take what i can get

Right on, I just wasn't understanding %, I was unfamiliar with it referenced to nothing. Its strictly relative. (Flow into combustion chamber vs Flow out of combustion chamber) I would venture to say that your average leak is 25% to the crankcase, and the two that are valves, the % is split to the valves and the crankcase. At least that seems right, 4 of 6 cylinders are 25% avg and two are higher.

Whats your lowest oil pressure? about 20psi hot idle?

As far as cyl 2&3, it could be the headgasket between the two leaking, but I don't think thats the major part of your performance hit. Only way I think you can actually check if its the valves or headgasket between the two is pull the valve cover, loosen both sets of rocker arms on cyl 2&3, pull the plugs on 2&3 and pressurize one and see if it comes out the other cylinder, or if it still comes out the valve... Only cost a tube of black silicone to see.. Someone tell me if there is another way..

good luck!

btw-- to check rings with a compression gauge throw a tablespoon of oil/trans fluid in each cylinder (dry 1st round, with oil 2nd round)