Volvo Penta 2003, steam from exhaust

[Hampus]

Hi,

First post in a long time, it will be a bit lengthy as there is some background information that may be important.

We occassionally rent out the boat when it suits us and 2 years ago the guys renting it had the fresh water cooling pump break down. They handled it well and I rebuilt the pump over winter. Everything was fine last season, no apparent damage to the engine, the cooling water stays where it's supposed to.

This year we had a raw water cooling hose that started to leak, nothing major, just a little drizzle just by the siphon valve. I changed both hoses and off we went. We motored for 19 hours in no wind and I noticed that there seemed to be an unusual amount of steam in the exhaust. There was one more incident with one of the new hoses coming loose because it was of inferior quality (replaced with a better one now). It wasn't loose for very long, there was only a few litres of water in the bilge but the engine ran with very little sea water for maybe a few minutes

There is cooling water is spurting out (like a shower) and occassionally there's the odd gush, but it seems like there should be more. There is also steam.

This is what I know:

There is no leakage of fresh water anywhere in the system.

The fresh water pump has just been rebuilt.

I change impeller every year and twice this year just in case.

The excessive steam seems to start after running a few minutes at around cruising speed (2000 rpm's).

The engine doesn't run hot.

No part of the exhaust system gets warmer than that I can keep my hand on it.

The raw water coming out the exhaust has a temperature of around 45 degrees C (113F) (around 20 going in).

I've checked for blockages between the siphon valve and raw water intake, found nothing.

The raw water is warm directly after the heat exchanger, indicating that the heat exchanger works.

Pumps and injectors were serviced 5 years ago.

We haven't hauled out in 2 years so there is some growth (barnacles) now.

Any ideas?

[sailormed]

Blocking in the exhaust elbow injection channel?

[Hampus]

Originally Posted by sailormed

Blocking in the exhaust elbow injection channel?

The injection channel itself (pipe connecting to the elbow) is clear but there could be a blockage further in.

[Stevenc]

Could it be just water mist rather than steam ?
Steam requires boiling temperatures which you don’t have.

[Hampus]

Originally Posted by Stevenc

Could it be just water mist rather than steam ?
Steam requires boiling temperatures which you don’t have.

Well, it's definitely steam. Steam can still be formed below boiling temperature, depending on air temperature and relative humidity. The conditions now aren't ideal for that though, so you are right in that the steam is probably close to boiling temperature. My guess is that the water isn't gushing into the exhaust system, but sputters. This could cause the smaller drops to reach boiling temperature and vaporize when coming in contact with the hot exhaust fumes while the lager drops stay liquid.

I'll try disconnecting the hose from the elbow today and run the starter with the decompressuon valves lifted. That should show how the water entering the exhaust system looks. If it's flowing or sputtering...

[Apollo366]

I had this problem once, turned out the exhaust elbow was clogged with carbon, had to replace it.

[Horus]

Is there a blocked fresh water filter in the system?
The VP 2003 has a closed cooling system, which is cooled by fresh water; is that right?
In case yes, there might probably be a part of the fresh water impeller broken and now blokking the water flushing clear trough the pump. I gues you have to check your fresh water pump once again. Can you blow water back from the pump? Or from the pump through the fresh water system to the exhaust? Not to much! Both yes; the pump must be blocked.

[Scrimshaw4]

It might be a combination of two problems. Cross contamination in the heat exchanger combined with a blown head gasket. The cross contamination would allow the coolant level to be maintained by resupplying the fresh water side that is loosing liquid thru the head gasket and causing the exhaust steam. Both conditions are easily diagnosed. JMHO

[Hampus]

Originally Posted by Apollo366

I had this problem once, turned out the exhaust elbow was clogged with carbon, had to replace it.

That could be the case. It doesn't get warm though. I ran it again today and I can quite comfortably hold my hand on the exhaust manifold when running at cruising speed. It gets slightly hotter while idling.

I also disconnected the hose going into the manifold to check water flow and it's gushing like it should, there appears to be no blockages.

The rest of the exhaust system is not very old, maybe 7-8 years.

[Hampus]

Originally Posted by Horus

Is there a blocked fresh water filter in the system?
The VP 2003 has a closed cooling system, which is cooled by fresh water; is that right?
In case yes, there might probably be a part of the fresh water impeller broken and now blokking the water flushing clear trough the pump. I gues you have to check your fresh water pump once again. Can you blow water back from the pump? Or from the pump through the fresh water system to the exhaust? Not to much! Both yes; the pump must be blocked.

Yes, it's fresh water cooled but there is no filter. The fresh water pump isn't an impeller pump, it's all metal with a bronze pump wheel. Both the wheel and bearings are new, that's the one I rebuilt.

[Hampus]

Originally Posted by Scrimshaw4

It might be a combination of two problems. Cross contamination in the heat exchanger combined with a blown head gasket. The cross contamination would allow the coolant level to be maintained by resupplying the fresh water side that is loosing liquid thru the head gasket and causing the exhaust steam. Both conditions are easily diagnosed. JMHO

Yeah but considering how much we've run it there wouldn't be any coolant left, only sea water. That is not the case. The expansion tank is still full of nice blue coolant. Also, shouldn't the pressure be higher on the fresh water side, considering how much warmer it is?

[Hampus]

This is what it looks like at 2000 RPM, reversing while tied to the dock.

https://youtube.com/shorts/JpXfLATTMGI?feature=share

[Apollo366]

Your water flow is totally inadequate!
It's just sputtering, it should come out as a slug once every 2-3 secs or so.

Water is getting to the elbow, just not through the elbow and out the exhaust port.

Do remember how it came out before, like a month or year ago?

[thunderhoof]

Nowhere do I see that you have disconnected the input and output rubber sleeves at the heat exchanger to look for foreign matter in the exchanger tubes.
When I had to replaced the exhaust /water mixing junction and exhaust manifold due to corrosion ruining both pieces I found lost bits of previous raw water pump impellers jammed into several of of the tube ends. Same engine 2003 Volvo Penta.
BTW, I strongly suggest you replace the exhaust / water junction with an aftermarket stainless steel piece. Cheaper than OEM and appears to be much more rugged.

[Hampus]

Originally Posted by thunderhoof

Nowhere do I see that you have disconnected the input and output rubber sleeves at the heat exchanger to look for foreign matter in the exchanger tubes.
When I had to replaced the exhaust /water mixing junction and exhaust manifold due to corrosion ruining both pieces I found lost bits of previous raw water pump impellers jammed into several of of the tube ends. Same engine 2003 Volvo Penta.
BTW, I strongly suggest you replace the exhaust / water junction with an aftermarket stainless steel piece. Cheaper than OEM and appears to be much more rugged.

Thanks!

No, I did not. The heat exchanger is difficult to get to, I'd have to move the entire engine. I did disconnect the hose after the heat exchanger and checked the flow, it seemed fine with a nice steady flow. I can't guarantee that there is no debris in the heat exchanger but I can guarantee that there are no impeller parts. I change impeller every year, so they never have more than about 6 weeks of use. I also check the ones I remove and I've never removed a damged impeller.