#1
IP: 69.172.163.17
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Piston anomoly
Hi
The attached jpg is a periscope photo taken of my number 4 piston after the engine has been sitting for a day. Questions: 1: What is the screw head like thing in the center? 2: Do the stamped markings mean anything to anyone? 3: Where does the fluid come from? Its not present in the other cylinders. Regarding question 3. With the flathead design oil wont seep into the cylinders through gravity while at rest, so my best guess is its unburnt additives I've added to my fuel. Seems a lot though and the engine runs great. Number 4 has the lowest compression of all 4 but only by about 5%. Thanks |
#2
IP: 155.186.122.195
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#1 That is the "center hole" for machining and grinding the piston, IE just a dimple.
#2 The stamped numbers are part numbers. #3 The fluid is probably water. Water will break up the carbon deposits during combustion. Do you shut off the water valve? Could be back-flow from the exhaust or a minor leak in the head gasket which may be the compression loss. Water can also seep in through a crack, has the engine overheated recently? Dave Neptune |
#3
IP: 138.207.177.95
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Most A4s slope aft and if any water back up the exhaust, it ends up in #4 first.
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#4
IP: 134.41.92.9
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The engine that I removed from the boat 3 weeks ago had one piston with that mark. It was number 1 cylinder, the high end of the engine on my boat. The other 3 cylinders didn't have anything like that. It did have minor pitting on the other 3 cylinders that I think happened the year prior to me buying the boat. I bought it in 2007 and all the valves were seized, the manifold was broke open from frost etc etc....I looked at that hole with a light and it was almost like it was a machining set.
__________________
Mo "Odyssey" 1976 C&C 30 MKI The pessimist complains about the wind. The optimist expects it to change. The realist adjusts the sails. ...Sir William Arthur Ward. Last edited by Mo; 10-27-2020 at 07:02 PM. |
#5
IP: 69.172.163.17
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Quote:
The valve seat area is always dry as a bone. Thinking it may be a head gasket leak now. I should take more pictures overtime and see how it goes. Last edited by cowlum; 10-27-2020 at 06:26 PM. |
#6
IP: 155.186.122.195
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It most likely is the head-gasket and perhaps another compression check will expose it.
Another possibility for water incursion and the engine still running could be the intake manifold is rusting through which is an easy check. Both are not uncommon. Dave Neptune |
#7
IP: 69.172.163.17
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I ran the engine for 15 minutes, in gear attached to the doc at 1400 rpm.
The fluid remained in the cylinder. I checked the other cylinders and they too had liquid, though less of it. Is it possible its marvel oil from the gasoline that isn't being burnt off? Or oil from my compression test a month ago, which would be about 2 hours runtime ago? My engine runs quite cool. She starts easily and runs perfectly. The spark plugs are a little sooty but clean on the electrode tips. On another note: I dont suppose theres enough numbers showing on the piston to suggest any history for the engine? Factory originals? rebuild etc? Last edited by cowlum; 10-27-2020 at 11:38 PM. |
#8
IP: 104.174.83.118
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Cooling system pressure test:
https://www.moyermarineforum.com/for...ad.php?t=11111
__________________
Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others |
The Following 3 Users Say Thank You to ndutton For This Useful Post: | ||
#9
IP: 100.40.58.241
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Cowlum,
The markings that are visible on your piston match those on mine, which are original parts. Here is a link to a photo: https://drive.google.com/file/d/1zTA...w?usp=drivesdk This does not rule out a previous overhaul of your engine. For example, the original pistons might have been OK, and only rings replaced. Jack. |
#10
IP: 209.6.133.136
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JC what do the registration markings on your pistons reference?
Do you have a larger album from an overhaul or rebuild would love to see. Thank you. Stay well. Tim
__________________
Tim Smith Oasis Pearson 30 1974, Number 572 Boston, MA USA |
#11
IP: 165.225.20.171
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__________________
Surcouf A nostalgic PO - Previously "Almost There" - Catalina 27 (1979) |
The Following User Says Thank You to Surcouf For This Useful Post: | ||
TimBSmith (10-28-2020) |
#12
IP: 100.40.58.241
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Tim,
Here are my notes on my overhaul: https://drive.google.com/file/d/0B86...ew?usp=sharing My notes merely describe what I did, not how it should be done. Some people on another forum were (oddly) upset that I did more work and spent more money than I should have. Somewhere near the end I comment on things I would do differently 'next time'. Hope this helps some. Good luck with your A4. Jack. |
#13
IP: 100.40.58.241
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Tim,
I forgot to answer your question about the numbers stamped on the piston: One of the numbers is "2.56055". My average cylinder bore measurement was 2.563. The standard cylinder bore in the MMI manual is 2.562. So, the stamp on the piston appears to be its diameter. The large "2" in my photo is the piston number/position, and the "Front" arrow indicates direction of installation (though "Front" is not what I first thought). I can't explain the remaining number on the piston ("2.60999"). Perhaps others know. Hope this helps. Jack. |
The Following User Says Thank You to jcwright For This Useful Post: | ||
TimBSmith (10-28-2020) |
#14
IP: 209.6.133.136
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Jack, thumbing through notes. Awesome documentation.
Registration notes on markup on piston helpful. Thank you for follow-up.
Favorite note so far in your discussion of rebuild or buy economics.. "An unexpected benefit was appreciating all the tools I’d inherited from my father, each one of which—right down to the smallest wrench and socket—he’d engraved with his initials decades ago." Priceless. Stay well, Tim
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Tim Smith Oasis Pearson 30 1974, Number 572 Boston, MA USA Last edited by TimBSmith; 10-28-2020 at 10:33 AM. Reason: discovery. |
#15
IP: 100.40.58.241
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Which reminds me--my dad engraved all of his tools with an engraving tool that I gave him for Christmas, I would guess when I was about 10 or so.
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TimBSmith (10-28-2020) |
#16
IP: 69.172.163.17
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I just cant seem to change the amount of fluid sitting on top of the piston. If I heat the engine up fully, then remove the spark plug it doesn't boil or evaporate despite the heat. Leads me to believe its oil rather than coolant. So I'm less worried. I'll let it sit a few days with plugs out and see if its evaporates. Another thing I did this afternoon was fill the tank with fresh stuff but I doubt the 10-15 minutes run time was long enough to get fresh stuff through the filter and into the engine. The tank was extremely low.
I'll still pressure test the block and manifold when I collect all the required part. I'm curious to try this anyway and it will completely settle what happens next. Thanks |
#17
IP: 71.215.209.38
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Quote:
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#18
IP: 155.186.122.195
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The fluid looks like antifreeze. Is the engine raw water or fresh water cooled? The antifreeze will evaporate very slowly. Any running of the engine if it were oil would produce copious amounts of smoke once started, did it?
Dave Neptune |
#19
IP: 184.151.230.149
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That’s a good idea, I’ll do that but ultimately aim for a pressure test.
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#20
IP: 184.151.230.149
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It does look like that but after 15 minutes of running in gear, too hot to touch it looks exactly the same. Water in the exhaust is steaming the usual amount.
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#21
IP: 104.174.83.118
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Please address this question:
__________________
Neil 1977 Catalina 30 San Pedro, California prior boats 1987 Westsail 32, 1970 Catalina 22 Had my hands in a few others |
#22
IP: 69.172.163.17
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Fresh water cooled. No obvious coolant loss.
I'm not ruling out the idea its water, im just confused as to why it wont turn to steam. I guess my assumption was oils harder to burn than water is to steam. But maybe I assume too much. My best guess at the moment its just something in the fuel that's not significantly effecting the way it runs... I need to get the pressure test parts and the time to test it. Last edited by cowlum; 10-29-2020 at 10:22 PM. |
#23
IP: 162.219.70.239
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Quote:
My engine does not "steam" from the exhaust. Just a suggestion. Peter PS - sort of like when I loaned my car to someone and half-way through explaining that the hockey stick through the hole in the floor is the brakes, I realized that maybe there IS something wrong with the car that should get fixed and that hockey stick brakes, while they were normal for me, are in fact not normal. |
#24
IP: 47.142.133.234
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Agree, it is antifreeze. Not water. If it were water it would
'burn off" - assuming the engine would start with that much water in the cylinders. I'm going to go against prevailing opinion and suggest that a compression would give some actionable information. The head gasket may be compromised some how some way. ex TRUE GRIT |
#25
IP: 69.172.163.17
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Thanks guys
First things first. I will preform the pressure test when I get parts and my newborn allows the time, im not using the boat now anyway . Its result will decide what happens next and is all that really matters. But I'm finding the speculation enjoyable non the less so to continue.... I did a few compression tests about a month ago, 95 on all cylinders and 90 for #4 on my original tester. Its been this every year since I bought the boat in 2013 with 200 hours on the engine since. Slightly higher across all four on the tester that came with the timing light kit a friend loaned me. I poured engine oil in cylinder 4 a month ago to see if it would raise compression in alignment with the others, it did not. I also used seafaom cleaner about a month ago. The steam from my exhaust is normal for the PNW at this time of year. All boats here steam. I've blown head gaskets on project cars in the past and a good amount of steam requires a good amount of radiator water. But yes, I agree the headgasket steam may be hidden in the normal PNW steam. My doubts as it to it being water or antifreeze is even when the engines very hot it remains, not steaming, not bubbling. The exhaust port is peppered in white ash which is inline with heat and burning oil. Oil has a much higher flash point than water or antifreeze ive learnt since yesterday. So im still hopeful its just the oil from the compression test. On the flip side I doubt oil cleans cylinders and pistions, this piston looks steam cleaned. So this points to head gasket. The engine runs perfectly and I would not have even been worried had I not put my borrowscope into the spark plug holes for curiosities sake... Lesson learned... or issue found early The pressure test will reveal all.,,, hopefully. thanks |
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