Dead cylinder

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  #1  
Old 11-07-09, 11:27 PM
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Dead cylinder

One of the cylinders of my 86 Corolla is dead. Compression check reads 0 psi. I'm thinking its maybe a valve stuck open. How can I determine if its a valve or maybe rings? Thanks
 
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Old 11-08-09, 06:07 AM
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Your best bet is a leak down test where you lock the engine @ TDC compression on that cylinder & put 15 or 20 PSI of air into the cylinder thru an adaptor in the spark plug hole & listen for where the air leaks from... The other way (altho not as accurate) is to put 2 Tbs of oil in the cylinder & do a compression test.. If the test with oil is 40 or 50 lbs higher than the test dry,, than it's rings... if it's the same,, valves or a head gasket,,, (This is all assuming the piston still goes up & down,, Right???? Hope this helps,,, Roger
 
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Old 11-10-09, 04:47 PM
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I don't have the tool or a compressor to do the leakdown test. As far as the piston still going up and down, the engine isn't making any unusual noise. It just runs rough, probably because of the dead cylinder.

Engine temp is normal. Would this eliminate the head gasket as a cause?

I still drive the car 90 miles everyday.

Will try the oil in the cylinders to see how it affects the readings.

Thanks. Dave
 
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Old 11-11-09, 05:08 AM
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Head gasket problem shouldn't run the compression all the way down to "0" and you would either be losing coolant or getting coolant in the oil depending on where the blow out was. As hopkins said, most likely a valve or ring problem. The "wet" compression test will narrow it down.
 
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Old 11-11-09, 07:57 PM
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The rings would have to be out of it altogether to get a 0 reading and would be unlikely if the other cylinders were getting good compression.

It's likely a valve or blown gasket leaking into the crankcase.
 
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Old 11-12-09, 12:03 PM
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How about a valve stuck shut?

Pull the valve cover and see what's going on. I've seen cam followers fail before.
 
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Old 11-12-09, 03:01 PM
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Originally Posted by aandpdan View Post
. I've seen cam followers fail before.
Tell me about it. Happened to me on two separate occassions on 2 different cylinders on my car. Luckily I was able to pop the roller rockers back in without undoing anything.
 
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Old 11-14-09, 10:52 PM
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Rechecked the compression with some oil in the cylinders. The dead cylinder is still dead. Guess it's a valve stuck open. Spark plug is wet and full of carbon. I don't suppose there is some way to redress the valve without taking the head off?
 
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Old 11-15-09, 07:13 AM
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Actually it may be easier than taking everything apart. Pull the valve cover and make sure the stuck valve is what you have.

That being the case, spray the valve stem and guide with penetrating oil, let it sit for abut an hour, then use something made out of brass or hard plastic and tap on the end of the valve stem. It could very well break loose and pop back into place - a lot of times they will. If it doesn't you can set up a little fulcrum/lever to pry some pressure up on the spring collar to get it to move.

If you're all well to that point get a can of aerosol carbon cleaner to spray into the intake and follow the directions on the can. Then change your oil and add something like Mystery oil or Sea Foam to the gas and oil.
 
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