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Old 07-17-2006, 11:35 PM
Paul A Paul A is offline
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Water in Cyl


I have experienced water backed up into my cylinders (3 and 4). My 79 Cat 30 A4 had been running in the 160-170 range about a month ago with the Volvo thermostat in it. Reading your tech manual I caught a note to restrict the bypass line after the T fitting. I did that and it brought the temp down to a steady 140. At the same time I added the restricter, I also did an acid flush (it had been about 3 years). Everything appeared to work well but I did notice that I wasn't getting near the water coming out of the engine that I did prior to this work. Eng Temp was great though.

The next time we took the boat out I noticed some steam in the exhaust (something I hadn't had before). I continued to use the boat on the weekends with no temp problems or noticable engine problems until last weekend. After motor sailing for a a couple hours the engine quit running. when I went to look I had water coming out of the throat of the Carb. I have never had a problem like this motor sailing before.

I pulled the plugs, filled cyl with MMI, cranked with H2O intake closed until water was out of cyl. I ran a compression check on all cyl. 4=120, 3=90, 2=115 and 1=120. The exhaust manifold was also full of H20. I pulled it off the engine, drained the water and inspected it. (it was replaced 2 years ago) I ran water through the upper portion with good flow out the exit port and no noticable water going into the dry section. I reassembled the engine and ran her for 1-2 minutes at a time with water intake closed while changing the oil until the oil looked clean. I also disassembled my entire exhaust to look for restrictions or blocks. I found nothing.

I opened the raw water intake and ran the engine noting again steam and less flow of water than normal coming from the exhaust. The engine backed up with H2O again. I repeated the steps above less the compression check and exhaust removal.

I then removed the thermostat and started the engine with water intake open. I finally got the correct amount of water leaving my exhaust that I have been used to seeing for years with no steam. The engine shut down about a minute later and the cyl (3, 4) and the dry side of the exhaust manifold were full of water again???

Would a thermostat cause this problem? Engine temp was always good following the addition of the restricter and the volvo thermostat. would the restricter cause this? Could it be the acid flush? The engine has run great for the 4 years I have owned the boat less having to replace the thermostat and exhaust manifold for a hole in it.

Any suggestions?

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Old 07-18-2006, 06:24 PM
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Don Moyer Don Moyer is offline
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From your report it seems clear that a small hole has opened up in one of your water jackets. The question is which one. The easiest item to check is the manifold. All you have to do is to remove the hoses from each end and blow in one end while holding your finger over the other. If you can blow through the manifold, that's your smoking gun.

If your manifold is solid, you can use the attachment to check the block and head.

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Old 07-18-2006, 06:25 PM
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Don Moyer Don Moyer is offline
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I forgot to address the second part of your question.

Nothing you are inquiring about as a possible cause of your water problem would have anything to do with the leak, with the possible exception of the acid flush.

Since the water leak seems to have developed immediately after an acid flush, it's entirely possible that the acid flush did cause a very thin area of a water jacket to break through. However, if a water jacket is really so thin that the mild acid solution prescribed in our procedure causes it to break through, it's best that you discovered that condition sooner rather than later. In fact, if your situation really does turn out to be as it appears, it would be the very first time that a water jacket failure was reported in the aftermath of an acid flush in the 15 years (or so) that we have been recommending the procedure.

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