Engine "steamy" type noise and consuming coolant

[autumnbreeze27]

Our engine started making a strange noise right at the start of our cruise south. To me it sounds like steam, it doesn't sound like a noise that relates to RPM mechanically... kind of like a pressure cooker sh-sh-sh but without any regular rhythm in both frequency or volume (ie, it's a random shssshhhshhhhSHHHshhhshhhhshhhhhshhhh. Otherwise the engine does not operate outside of normal, no steam in the exhaust that I can see (it is under the stern, so it would have to be significant to be visible, but I look out the stern lights and don't see anything), no difference in performance or temperature, but she consume coolant. 2-3 hours of running and the reserve (the plastic bottle that has the FULL WHEN COLD/FULL WHEN HOT marks on it) empties out.

It hasn't really gotten worse for 50 hours of running or so. I flushed the coolant (it was muddy, had to fill and flush 4-5 times to get it to be clear again), and I've changed the oil.

Any ideas on what I should check?

Engine is a Cummins 4BT Turbo Diesel. I tried poking around it with a mechanics stethoscope yesterday but couldn't figure out where it's coming from.

[Paul L]

Do you have engine heated hot water tank? If so, check those hose connections.

[autumnbreeze27]

No, there's a heat exchanger for the tranny, that's it.

I had both heat exchangers cleaned out about a year ago.

[a64pilot]

I'd guess the hissing sound may be wastegate and or a a loose hose or induction system leak. Would have nothing at all to do with water consumption though, that sounds a lot like a head gasket or an external leak of some kind.

[a64pilot]

Originally Posted by autumnbreeze27

I had both heat exchangers cleaned out about a year ago.

That wasn't 50 hours ago was it? Cause of course it's possible to lose coolant into the seawater side of a heat exchanger.
I'd start with pressure testing the cooling system, I don't think Cummins are that prone to blown head gaskets, not without being severely overheated or something

[autumnbreeze27]

I think it might be my heat exchanger. Now that I've wrote it all up and looked at your responses... I blame the moron who worked on it last. That would be me.

[a64pilot]

Yeah, well if it's just an O ring or something, that is about the best thing it could be


Sent from my iPad Pro using Cruisers Sailing Forum

[jimbunyard]

Bad or incompletely screwed on (I've done it several times) radiator cap?

[goat]

Originally Posted by autumnbreeze27

I think it might be my heat exchanger. Now that I've wrote it all up and looked at your responses... I blame the moron who worked on it last. That would be me.

BTDT. Whenever a problem crops up, I always ask, "what was the last thing I worked on?" Saves a lot of trouble shooting.
Good luck.

[01kiwijohn]

Pressure test the system, then you'll know for sure, before pulling anything apart.

[zeehag]

also check color of oil in engine. you do that by checking oil level. that is what the dipstick is for.
you want to check level and color of oil

[Dave22q]

Replace your radiator cap as a first step. Cost is minimal and it might just solve your problem. If not close to a store, make a paper collar and place around the radiator cap. Take her for a run until you hear your steam. If water marked paper you have your answer. If not, check your coolant hoses and connections by removing and examining before replacing. I once found a clamp that looked good until I went to remove it and found the bottom had corroded to nothing. At this stage I would not be too concerned about leaks within the engine because I think it is less likely that you would hear the leak. Hopefully these cheap steps will solve your leak.

[tankersteve]

No advice, although good luck with your troubleshooting.

Is your 4BT a specific model or specially 'marinized'? Just curious, as that is a very robust diesel and a pretty neat choice for a sailing vessel. Parts would, I think, be pretty available!

Tankersteve

[Scaramanga F25]

If you could borrow an automotive radiator pressure tester that would be a great help.
It replaces the rad cap on header tank and pump in pressure.
If it drops you have your answer. Then trace.

I had a mechanic try to charge me 1200$...head gasket.
Borrowed a tester from a local garage and found collapsed hot water
hoses under the cabin sole.

[TranceNT]

Coolant leaks sometimes reveal their general location by staining with the dried chemical fractions they contain. Look for colour change or drip track.

Water pump seals may leak only when the engine is running, although that can be allowed for in a pressure test with a bit of pushing and pulling on the pump pulley.

As already posted, leaking turbo high side connections do produce a sound which varies with RPM, but this can be load dependent and not evident at idle or no-load elevated RPM.