Bent pushrod on 1985 (maybe)??
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Instructor
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From: Durham NC
Safety Car
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#6 certainly jumps out....
a loss of about 40 or 50 psi is what I'd suspect from a piston that's not making it all the way to the top of the stroke........because something is bent/broken and the rod length is shortened. It doesn't take much at all to lose lots of compression.
I would go back to #6 and squirt some oil in the spark plug hole then do the test again and cycle the engine several times.
What to look for:
IF it builds MORE than 120 psi then you have an issue with the rings. Oil helps seal them temporarily.
IF there is no change, then that narrows it down to either a valve problem(leaking) OR something in the piston/rod/bearing.
The other cylinders are right about where a stock motor should be. 160 is 'bout average.
has the oil been drained and strained yet? You can SEE bearing damage in the oil.
The bearing material looks like silver paint swirled around in the oil....Very obvious.
Straining the oil thru a thin cloth will catch any small metal particles that might have come from a cracked or broken piston skirt, rod hole or even a bearing. Most of the metals that would be damaged are NOT magnetic, so they will not be on a magnetic drain plug...
a loss of about 40 or 50 psi is what I'd suspect from a piston that's not making it all the way to the top of the stroke........because something is bent/broken and the rod length is shortened. It doesn't take much at all to lose lots of compression.
I would go back to #6 and squirt some oil in the spark plug hole then do the test again and cycle the engine several times.
What to look for:
IF it builds MORE than 120 psi then you have an issue with the rings. Oil helps seal them temporarily.
IF there is no change, then that narrows it down to either a valve problem(leaking) OR something in the piston/rod/bearing.
The other cylinders are right about where a stock motor should be. 160 is 'bout average.
has the oil been drained and strained yet? You can SEE bearing damage in the oil.
The bearing material looks like silver paint swirled around in the oil....Very obvious.
Straining the oil thru a thin cloth will catch any small metal particles that might have come from a cracked or broken piston skirt, rod hole or even a bearing. Most of the metals that would be damaged are NOT magnetic, so they will not be on a magnetic drain plug...
Last edited by leesvet; Oct 10, 2014 at 03:11 PM.
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Instructor
Joined: Oct 2002
Posts: 218
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From: Durham NC
#6 certainly jumps out....
a loss of about 40 or 50 psi is what I'd suspect from a piston that's not making it all the way to the top of the stroke........because something is bent/broken and the rod length is shortened. It doesn't take much at all to lose lots of compression.
I would go back to #6 and squirt some oil in the spark plug hole then do the test again and cycle the engine several times.
What to look for:
IF it builds MORE than 120 psi then you have an issue with the rings. Oil helps seal them temporarily.
IF there is no change, then that narrows it down to either a valve problem(leaking) OR something in the piston/rod/bearing.
The other cylinders are right about where a stock motor should be. 160 is 'bout average.
has the oil been drained and strained yet? You can SEE bearing damage in the oil.
The bearing material looks like silver paint swirled around in the oil....Very obvious.
Straining the oil thru a thin cloth will catch any small metal particles that might have come from a cracked or broken piston skirt, rod hole or even a bearing. Most of the metals that would be damaged are NOT magnetic, so they will not be on a magnetic drain plug...
a loss of about 40 or 50 psi is what I'd suspect from a piston that's not making it all the way to the top of the stroke........because something is bent/broken and the rod length is shortened. It doesn't take much at all to lose lots of compression.
I would go back to #6 and squirt some oil in the spark plug hole then do the test again and cycle the engine several times.
What to look for:
IF it builds MORE than 120 psi then you have an issue with the rings. Oil helps seal them temporarily.
IF there is no change, then that narrows it down to either a valve problem(leaking) OR something in the piston/rod/bearing.
The other cylinders are right about where a stock motor should be. 160 is 'bout average.
has the oil been drained and strained yet? You can SEE bearing damage in the oil.
The bearing material looks like silver paint swirled around in the oil....Very obvious.
Straining the oil thru a thin cloth will catch any small metal particles that might have come from a cracked or broken piston skirt, rod hole or even a bearing. Most of the metals that would be damaged are NOT magnetic, so they will not be on a magnetic drain plug...
Burning Brakes
Joined: Mar 2013
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From: Illinois/Wisconsin Line
Le Mans Master
Joined: May 2006
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From: indy indiana
don't feel to bad, folks been using water down the carb for years and years..a real old timmers trick that should be left alone in these days of fuel injection. seen it done years ago.. and it worked..done by a factory mechanic, ford.
Safety Car
Joined: Apr 2011
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Knowing all the other details, the sound, the hydro-locking, the compression difference, that's what I'd say too. #6 rod is now a bit shorter than the others...
Like it has been said, since you canot compress water, for the crankshaft to rotate, something has to bend or break. In this case I believe the #6 connecting rod bent just enough to allow the crank to complete its cycle until a valve opened and let the water escape.
Once this has been confirmed, an "in-frame" piston pull is NOT out of the question....
its been done before to change out a rod. As long as the piston/rings are ok, its possible.
Like it has been said, since you canot compress water, for the crankshaft to rotate, something has to bend or break. In this case I believe the #6 connecting rod bent just enough to allow the crank to complete its cycle until a valve opened and let the water escape.
Once this has been confirmed, an "in-frame" piston pull is NOT out of the question....
its been done before to change out a rod. As long as the piston/rings are ok, its possible.
Safety Car
Joined: Sep 2004
Posts: 3,953
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From: Mission Viejo CA
Attachment 47833011
With a bent con rod, the crankshaft counterweights will hit the bottom of the wrist pin bosses, rather than the piston skirt. Depending on how severe the hydrolock was, the piston may jam against the crankshaft, or the piston may be shattered. It's amazing to me that you were able to drive your car more than 14 miles without more dramatic sound effects!
Since you pulled the spark plugs and the engine still wouldn't crank, you certainly had the bottom of the #6 piston jammed against the crankshaft at BDC! Be very happy that you have 120 psi on cyl. #6! That says you didn't shatter your piston! Lucky, lucky you!!
With a bent con rod, the crankshaft counterweights will hit the bottom of the wrist pin bosses, rather than the piston skirt. Depending on how severe the hydrolock was, the piston may jam against the crankshaft, or the piston may be shattered. It's amazing to me that you were able to drive your car more than 14 miles without more dramatic sound effects!
Since you pulled the spark plugs and the engine still wouldn't crank, you certainly had the bottom of the #6 piston jammed against the crankshaft at BDC! Be very happy that you have 120 psi on cyl. #6! That says you didn't shatter your piston! Lucky, lucky you!!
Last edited by Hot Rod Roy; Oct 21, 2019 at 07:02 PM.
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From: Durham NC
Some interesting info about this car. I bought it in Nov. of 1997 with 72,000 miles on the odometer. The car has always been an oil burner. It burns oil at the rate of about 1 quart per 1000-1200 miles. Within the last few years, plug #5 had to be cleaned or replaced every 4-6 months because of oil fouling. Lately that has increased to about every 6 weeks. That is why I am very surprised at the compression readings -- especially on cylinder #5. I was expecting something a bit lower. The car now has 227,000 miles on it. I was planning to do something as far as engine work sometimes next Spring or Summer anyway. And, yes I did drive it to a shop with the knocking and it ran OK. I thought the temp was a little high coming back home, but nothing alarming. Ans, it did seem a little sluggish on acceleration. The knocking did not seem to be affected by engine load. Actually, once in traffic, I could not even hear the knocking -- road noise I guess masked the sound. This has been a very interesting chain of events. The little bit of water the engine ingested seems small for the damage it has caused. Believe me, it was less than or about 1 cup of water involved.
Burning Brakes
Joined: Mar 2013
Posts: 1,131
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From: Illinois/Wisconsin Line
I hear man and thought and was hoping for ya the same thing but you can put all this to rest with just pulling 2 spark plugs.
Try this. It should take 10 mins.
Pull #1 spark plug, bump it up to close to TDC on it's compression stroke. Try and find something kinda flexible and long then slowly insert it with in the spark plug hole and push it down til it doesn't go anymore, as to get it to touch the piston. Mark it with ur thumb at the base on the head where the spark plug goes in and pull it out.
You now have a known good distance.
Do the same for # 6.
The difference won't be much
Try this. It should take 10 mins.
Pull #1 spark plug, bump it up to close to TDC on it's compression stroke. Try and find something kinda flexible and long then slowly insert it with in the spark plug hole and push it down til it doesn't go anymore, as to get it to touch the piston. Mark it with ur thumb at the base on the head where the spark plug goes in and pull it out.
You now have a known good distance.
Do the same for # 6.
The difference won't be much