Compression Issues: Bad Rings or valvetrain, Pics inc,
10-16-2013, 01:54 PM
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Compression Issues: Bad Rings or valvetrain, Pics inc,
First off, car is MY 2000 with 140,000 miles. Never been over-revved. I have bought it in 2005 when it had 32,000 miles.
It all started with a check engine light showing misfires on all cylinders. (P1399, P0301-P0304) A compression test showed cyl 1,3&4 all to be around 240 psi, but cyl 2 to be around 120 psi. I didn't have a leakdown tester at the time, so I didn't perform that test but I decided to go ahead and check the valve clearances. I didn't find anything too wacky, 1 or 2 valves were out by .001 or .002, but they were not in the problematic cylinder. Cyl 2's valves were right on. I adjusted the others to be closer to spec and reassembled but still had CELs and same compression test results. I also tried a dry vs. wet compression test, and with the wet the compression on Cyl 2 came up to 140 or 160 . (I don't have the numbers in front of me) From here I figured "uh oh, it's probably piston rings," but I wanted to see if I could find any other clues. I should note that I never noticed any smoking from the exhaust, no strange noises, but the idle has gotten kind of rough lately, small pops or puffing sounds from the exhaust.
I then ponied up and bought a leakdown tester. I had trouble getting it to read consistently, but since I knew Cyl 2 was the culprit, I ignored the readings and just listened to see if I could determine where the air was leaking from. It was pretty difficult to tell, but my best guess was that the air was leaking into the neighboring #3 cylinder. I couldn't hear a leak in the intake or exhaust at all, only quiet hissing from #3. From here I thought I would replace the head gasket, even though my initial inkling was bad rings. Atleast I could do the head gasket myself in the garage and wouldn't cost a fortune. Also, I figured that once I got the head off, I might get a few more clues.
Last weekend, I finally got the head off. The gasket looks to be in as good shape as possible. I checked all the valve retainers closely and found nothing wrong there. Cylinder walls showed no scoring or marks. Pretty much everything looked as I expected. I did, however, notice 2 things that might be clues.
First, on the #2 cyl, one of the exhaust valves is dark, much darker than the rest. I don't really know what this may or may not indicate. Any ideas?
Secondly, I noticed what looks like a "hot spot" on the #2 piston near the cylinder wall on the intake side. It is pretty small, and all of the other cylinders have a similar discoloration near the middle of the piston, but this is the only one that is around the edge of the piston. It is pretty minor, though. I thought it might be from oil or exhaust "washing" past the rings. All of the other cylinders show a similar discoloration around the IN stamping. Is this typical?
Im just trying to see if either of these two things could help determine if the rings are indeed bad, or maybe it is something else in the head. I appreciate the help.
It all started with a check engine light showing misfires on all cylinders. (P1399, P0301-P0304) A compression test showed cyl 1,3&4 all to be around 240 psi, but cyl 2 to be around 120 psi. I didn't have a leakdown tester at the time, so I didn't perform that test but I decided to go ahead and check the valve clearances. I didn't find anything too wacky, 1 or 2 valves were out by .001 or .002, but they were not in the problematic cylinder. Cyl 2's valves were right on. I adjusted the others to be closer to spec and reassembled but still had CELs and same compression test results. I also tried a dry vs. wet compression test, and with the wet the compression on Cyl 2 came up to 140 or 160 . (I don't have the numbers in front of me) From here I figured "uh oh, it's probably piston rings," but I wanted to see if I could find any other clues. I should note that I never noticed any smoking from the exhaust, no strange noises, but the idle has gotten kind of rough lately, small pops or puffing sounds from the exhaust.
I then ponied up and bought a leakdown tester. I had trouble getting it to read consistently, but since I knew Cyl 2 was the culprit, I ignored the readings and just listened to see if I could determine where the air was leaking from. It was pretty difficult to tell, but my best guess was that the air was leaking into the neighboring #3 cylinder. I couldn't hear a leak in the intake or exhaust at all, only quiet hissing from #3. From here I thought I would replace the head gasket, even though my initial inkling was bad rings. Atleast I could do the head gasket myself in the garage and wouldn't cost a fortune. Also, I figured that once I got the head off, I might get a few more clues.
Last weekend, I finally got the head off. The gasket looks to be in as good shape as possible. I checked all the valve retainers closely and found nothing wrong there. Cylinder walls showed no scoring or marks. Pretty much everything looked as I expected. I did, however, notice 2 things that might be clues.
First, on the #2 cyl, one of the exhaust valves is dark, much darker than the rest. I don't really know what this may or may not indicate. Any ideas?
Secondly, I noticed what looks like a "hot spot" on the #2 piston near the cylinder wall on the intake side. It is pretty small, and all of the other cylinders have a similar discoloration near the middle of the piston, but this is the only one that is around the edge of the piston. It is pretty minor, though. I thought it might be from oil or exhaust "washing" past the rings. All of the other cylinders show a similar discoloration around the IN stamping. Is this typical?
Im just trying to see if either of these two things could help determine if the rings are indeed bad, or maybe it is something else in the head. I appreciate the help.
10-16-2013, 08:45 PM
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