Comp test and leak-down, now what?
#1
New Member
Thread Starter
Comp test and leak-down, now what?
I know there’s other threads similar to this one but none specific to my scenario.
I have a 09 cobalt ss/tc LDK swap that threw a cylinder 3 ms while driving on the freeway. When it threw the miss, grayish white smoke came from exhaust, no blue or black. Running 50/50 E85 and 91 octane fuel.
ran a comp test: #1: 130, #2: 130, #3: 0! #4 145
then did a leakdown. Cylinder 3 had 10% leak, all others less than that. So this was less than helpful.
Under the hood, the engine sounds fine. Down by the exhaust pipe, sounds like ****. Sputtery sounding.
im at a loss. I’m thinking maybe a valvetrain problem, but I’m not 100% sure. I’m doubting cracked piston or rings now.
anybody have any other thoughts or diagnostic steps to take I didn’t think of (other than a shop)?
I have a 09 cobalt ss/tc LDK swap that threw a cylinder 3 ms while driving on the freeway. When it threw the miss, grayish white smoke came from exhaust, no blue or black. Running 50/50 E85 and 91 octane fuel.
ran a comp test: #1: 130, #2: 130, #3: 0! #4 145
then did a leakdown. Cylinder 3 had 10% leak, all others less than that. So this was less than helpful.
Under the hood, the engine sounds fine. Down by the exhaust pipe, sounds like ****. Sputtery sounding.
im at a loss. I’m thinking maybe a valvetrain problem, but I’m not 100% sure. I’m doubting cracked piston or rings now.
anybody have any other thoughts or diagnostic steps to take I didn’t think of (other than a shop)?
#3
Senior Member
iTrader: (6)
If the compression is 0, but leak down is 10% the engine shouldn't sound fine. If the intake valves are not opening that could provide a 0 compression and 10% leak down, but that doesn't make sense if the engine runs fine.
I'd re test the compression for cylinder 3, and try a wet compression test as well (add a bit of oil to the cylinder).
I'd re test the compression for cylinder 3, and try a wet compression test as well (add a bit of oil to the cylinder).
#5
Senior Member
I am betting it spit some rockers out.
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