4jh3 exhaust shine

[Liunatic]

Just had shop repair heat exchanger housing. Reinstalled and ran motor, notice a shine on the water from discharge. It doesn't have the bright distinct colors of oil, or diesel. Not sure what it is. Could it be antifreeze, mixing with the raw water? watching the exhaust from up on deck, its small droplets that fly out 2-3' as you watch them spray on the water. Unburnt diesel? Oil is fine. Ran the boat out for 4-5 hours last Monday, RPMs seem fine, power seems normal.

Liunatic

[tkeithlu]

Could be lots of things, but you need a best hypothesis to test. My best bet is that it is coolant from the engine getting into the raw water in the heat exchanger. That could be a pin hole in the coolant coils, or could be that there's a leak at any seal where coolant goes into the heat exhanger, if your exchanger is of the sort that slides out of the case, like my main engine one. Hope for the latter; it may just be a bad o-ring or gasket.

At any rate, determine whether or not it is coolant. First, is your coolant level dropping? Big clue right there. Catch some in a jar as it comes out the exhaust and take a good look once it settles. Coolant will tint the exhaust water; oil will bead.

Here's hoping your exhanger core is OK.

[Liunatic]

Well I left a pretty broad picture but here's a little more info. When I removed front end cap on HE the corrosion had taken a chip out of the side. Removed HE and had welder run some beads, and after some grinding had it shaped up pretty well, 150.00 was worth it. Upon reassembly there was 1 spot at 3oclock that allowed O-ring to push in to far, and end cap bottomed out against housing before is tightened the O-Ring. So I mixed some marin- tex epoxy and filled it in, let it set and installed O-ring and cap next day, and no leaks. Now I'm thinking its leaking into end cap and getting blown out exhaust? I thought I had read that pressure in coolant system is less than pressure in raw water system, so if O-ring was leaking I would be getting a higher level in sub tank? I do believe I'm loosing antifreeze so need to get a test kit and pressure test coolant system

[a64pilot]

Coolant pressure is higher than raw water pressure, raw water pressure is nearly zero as it’s open ended with nothing to make it build pressure.
Normally coolant isn’t detectable in the exhaust it mixes with water.
Yanmar’s are particular clean burning Diesels but if you haven’t had the injectors cleaned and inspected in quite awhile, maybe it’s time.