'03 Chevy Malibu, v6, 3.1, coolant loss, loud knock, loss of power, missfire?

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  #1  
Old 11-10-14, 07:29 AM
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'03 Chevy Malibu, v6, 3.1, coolant loss, loud knock, loss of power, missfire?

I have a 2003 Chevy Malibu, V6, 3.1, auto, 140k miles. Car started out with code 0420 with no noticeable symptoms, but then added code 0303 (miss fire cyl #3) with loud knock (mostly after warmup) and loss of power under load. Now internal loss of coolant (no puddles or external drips). Changed plugs and wires - no change - all plugs looked good with no sign of contamination. Questions - if this is a valve/piston/lifter problem, why would I get the loss in coolant? If the loss of coolant is fouling plug #3 (which would explain the miss fire and loss of power), could that give me the loud knocking? I don't see how a valve/piston/lifter issue would cause a leak in coolant but I also don't see how a coolant leak into cyl #3 would give me such a loud knock. Do I have two different problems? If it is a leak into cyl #3, is there any way to tell if it is the intake manifold gasket (which leaked before and was replaced five-six years ago and which I could do again if I had to) or a blown head gasket (which I don't think I could fix or afford to get fixed)? Engine will occasionally get hot (but not overheat).
 
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  #2  
Old 11-10-14, 07:51 AM
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The third spark plug looked good? No chalk disposal or anything else? Can you take a look into the cylinder if the piston is wet.
If the engine fills with coolant it probably causes the misfire.
Maybe a cracked engineblock?!
 
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Old 11-10-14, 06:46 PM
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Why do I have that feeling that you have internal head gasket leak and hydrolocked #3?
 
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Old 11-11-14, 04:59 AM
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I tend to agree with Igor. First step should be a compression test. When you say all plugs looked good, did one or more look really, REALLY good like it had been steam cleaned?
 
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Old 11-11-14, 06:16 AM
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How does your coolant look like? Maybe oily? Do a so called carbon monoxid test to see if the head gasket leaks!
 
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Old 11-11-14, 02:16 PM
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Coolant looks fine, oil looks fine.
I still have to ask, will a coolant leak (creating a fouled, miss-firing plug) cause a loud knock? Will a bad value/rod/piston cause a coolant leak? And is there a way to know if it is a head gasket leak or a manifold gasket leak (since the coolant runs through both)?
 
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Old 11-11-14, 06:53 PM
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When you hydrolock a cylinder, piston moves up and against non-compressive medium. This easily results in bent metal or busted bearing. That may result in knock. Piston tie rod; not sure if you have OHC engine or pushrod engine, but then pushrods bent; rockers can get damaged. Many things can go bad when piston hits something that is less compressive than concrete wall.
As of "is it gasket or what" - there are special tests for busted head gaskets. Coolant system is pressurized and pressure monitored. Leak down tests.
 
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Old 11-12-14, 07:41 AM
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And is there a way to know if it is a head gasket leak or a manifold gasket leak (since the coolant runs through both)?
A compression test will tell you if it is a head gasket.
A coolant system pressure test will tell you if you have a leak, head gasket or manifold
 
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