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Old 04-16-2016, 10:31 AM   #1
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LEHMAN 120- exhaust presure in coolant system

Bought my boat in the FL panhandle. Had mechanic do oil changes to bring her home to Charleston. He called to inform me starboard engine ran hot while warming her up and had milky oil. I went down and cleaned all coolers/exchangers. replaced all hoses, rebuilt raw water pump and replaced head gasket and head refurbished. With head off saw some pitting in 2nd cylinder from front as if water had been getting in there for a while, also the mechanic had concerns that that cylinder may have a hairline crack although I couldn't tell a difference from the others. He took a torch into the cylinder trying to raise water beads in the suspect area but never found any. The head checked out good and we never could prove the head gasket failed although it was degraded around that cylinder (could of been from disassembly). I reassembled the engine. After firing her up it was obvious I had air bubbles in my coolant reservoir although engine ran perfect, no coolant in oil, coolant level good, no hot/cool spots on infrared thermometer. Decided to bring her home. Engine ran great but.......about every 20 hours of run time I had to add a gallon of coolant.....we made the 1000 mile trip home and now I have her blocked up for refit. After a few days of sitting up, the engine was hydro locked and the coolant was low. After draining the coolant and letting her sit 24 hours it fires right up. At first I suspected the block must be cracked but after talking to American diesel, he feels this is unlikely and the first thing to check is the exhaust manifold......Boy! am I a dumb A$$....this never occurred to me but makes perfect sense considering my symptoms. I know this is a long post but I have to figure this out and didn't want to leave out any details. If in fact the engine needs to come out I want to get-r-done before tackling all the other 5986 things I have to do to this old girl. I have the manifold out and am pretty mechanically inclined. What technique would be best to check out this manifold? Sound like I'm on the right track?
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Old 04-16-2016, 11:11 AM   #2
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Send the manifold out to be propery tested for cracks.

If the engine really needs a rebuild it should be able to be done in the boat.

http://www.rlengines.com/Web_Pages/Magnafluxing.html
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Old 04-16-2016, 11:20 AM   #3
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Quote:
Originally Posted by Capt.Bill11 View Post
Send the manifold out to be propery tested for cracks.

If the engine really needs a rebuild it should be able to be done in the boat.

Magnufluxing Crack Inspection Crankshafts Engine Blocks Cylinder Heads: MA,CT,RI,VT,NH,ME,NY,NJ
How would one rebuild a non-liner engine in a boat sir? Especially one with a potential crack in the cylinder. I love learning new things.
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Old 04-16-2016, 11:27 AM   #4
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How would one rebuild a non-liner engine in a boat sir? Especially one with a potential crack in the cylinder. I love learning new things.
I thought the crack was in the manifold not the block?

"At first I suspected the block must be cracked but after talking to American diesel, he feels this is unlikely and the first thing to check is the exhaust manifold."
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Old 04-16-2016, 11:43 AM   #5
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For a FL 120 rebuild, Bomac Marine in GA may be an option. It looks like pretty detailed rebuild for $10K.

http://www.bomacmarine.com/pdf/reman...ehman-ford.pdf
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Old 04-16-2016, 11:53 AM   #6
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if it turns out a cracked manifold........no rebuild necessary......
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Old 04-16-2016, 12:20 PM   #7
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lacking any better ideas you can use rubber plumbing caps and clamps add a Schrader valve and pump air into the water side while in a water tank looking for bubbles or pressure loss.
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Old 04-16-2016, 12:40 PM   #8
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Exhaust manifold best tested using water under pressure in cooling jacket. Just cap off and plug all ports and hose fittings but one, attach a water source there. I use my well pump which I adjust p-switch to 30psi for the test. Leave water under pressure with manifold set on blocks so you can observe the exhaust ports. Looking for water to drip out. Assuming manifold is off the engine.
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Old 04-16-2016, 12:41 PM   #9
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Bayview and Ski

Seen it where cracked heads and manifolds only show leak when up to temperature, pressure test not always revealing on a cold engine. Magna flux on cold parts certainly can show all.

To the OP, did you do a mechanical survey prior to purchase or is this a new problem?
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Old 04-16-2016, 12:47 PM   #10
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Agreed, water test of the manifold is "inconclusive" if no leak found. It IS conclusive if a leak is found.

Another bit: A leaky exhaust manifold on a NAT engine will not cause bubbles to show up in coolant. Not enough pressure in manifold to leak from ex side to coolant side. Bubbles in coolant means there is leak from combustion chamber into coolant. Head, head gasket, cracked cyl are the poss culprits. Cylinders should be checked with dye penetrant test with pistons lowered into bores, can test two at a time. Head off to test, of course.

And get the water out of the oil sump and get any milky oil out. That stuff will ruin bearings given enough time.
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