STEAM out the exhaust

[Chanbo]

I recently (8 months ago )did a complete upper on my Catalina 30 with an M25. Its ran great until recently when it started blowing steam out of the exhaust. It only does it when the Radiator cap is on and it starts in about 30 seconds when I put the cap on. I put a pressure gauge to test and it help pressure but as soon as the motor starts there is immediate pressure on the cap..I changed the water pump both, cap, thermostat and upgraded from 2 to 3in heat exchanger. The rad fluid is not leaking as the level stays where it is supposed to so I am assuming the fresh water is somehow turning to steam ..do you think its the head gasket or is there somewhere else this can happen...

 

[Davidasailor26]

I recently (8 months ago )did a complete upper on my Catalina 30 with an M25. Its ran great until recently when it started blowing steam out of the exhaust. It only does it when the Radiator cap is on and it starts in about 30 seconds when I put the cap on. I put a pressure gauge to test and it help pressure but as soon as the motor starts there is immediate pressure on the cap..I changed the water pump both, cap, thermostat and upgraded from 2 to 3in heat exchanger. The rad fluid is not leaking as the level stays where it is supposed to so I am assuming the fresh water is somehow turning to steam ..do you think its the head gasket or is there somewhere else this can happen...

If the radiator fluid is not changing then the only possible source of steam is the raw water side. Do you have a temperature gauge, or at least a high temp alarm to tell if the engine is overheating? Is there still the normal amount of water coming out the exhaust?

 

[Richard19068]

Have you retorqued the head since doing the "complete upper"?

 

[Jim26m]

You comment that there is pressure on the cap immediately when you start the engine. Did you note what that pressure was?

It appears you changed your engine water pump AND your raw water pump from your post. Is that correct?

Also, it appears that you changed the heat exchanger. Correct? If so, was the replacement heat exchanger new?

As @Davidasailor26, says above, please verify that you are getting unrestricted raw water flow through the system.

Great problem, by the way! Steam with no apparent coolant loss is interesting. It would seem to rule out head gasket, but need more info. If you have pics of your engine, in current configuration, consider posting them.

Immediate pressure on the radiator cap is interesting as well. Very curious about the magnitude of this pressure.

Sounds like you have a good bit of engine knowledge. Is this correct, or did you have someone do the work for you? Not judging, just building the information trail.

It might be possible that the cooling system could hold 15-20psi but leak under compression through the head gasket. That still doesn't explain the steam, though.

 

[LeeandRick]

If steam is close to immediate after start up, then coolant through the engine. If it's after engine warm up poor raw water flow. I'm not an engine expert but this is what basic physics would indicate.

 

[Kings Gambit]

Steam comes out of my exhaust when something gets sucked into the seawater intake, blocking the cooling water, but not completely. Close the seacock, pull off the hose; take a look.

 

[capta]

I agree with the thought that after the original 'upper' the head must be re-torqued after some hours.

 

[Head Sail]

Have you checked your raw water strainer? Clean if necessary. Open the seacock breifly with the strainer off. Does water flow through rapidly? If not, shove a dowel or wire down the seacock until water flows.

 

[Chanbo]

You comment that there is pressure on the cap immediately when you start the engine. Did you note what that pressure was?

It appears you changed your engine water pump AND your raw water pump from your post. Is that correct?

Also, it appears that you changed the heat exchanger. Correct? If so, was the replacement heat exchanger new?

As @Davidasailor26, says above, please verify that you are getting unrestricted raw water flow through the system.

Great problem, by the way! Steam with no apparent coolant loss is interesting. It would seem to rule out head gasket, but need more info. If you have pics of your engine, in current configuration, consider posting them.

Immediate pressure on the radiator cap is interesting as well. Very curious about the magnitude of this pressure.

Sounds like you have a good bit of engine knowledge. Is this correct, or did you have someone do the work for you? Not judging, just building the information trail.

It might be possible that the cooling system could hold 15-20psi but leak under compression through the head gasket. That still doesn't explain the steam, though.

Yes changed both pumps..New heat exchanger from Mr Cool ..blows tons of water out the back ..I pressure tested and it held at about 35psi ..its weird because I keep the cap off and see the water circulating after it warms up but when I put the cap on not sure of the psi but its a lot and steam comes out eh back end ..I am by no means an expert although I was an aircraft mech for 8 years and worked on everything from C130s to PV2..DC4s etc so not totally in the dark.

 

[Chanbo]

If steam is close to immediate after start up, then coolant through the engine. If it's after engine warm up poor raw water flow. I'm not an engine expert but this is what basic physics would indicate.

Steam starts after engine is running maybe 1 min but only with cap on

 

[Chanbo]

Have you checked your raw water strainer? Clean if necessary. Open the seacock breifly with the strainer off. Does water flow through rapidly? If not, shove a dowel or wire down the seacock until water flows.

Checking all that today but its blowing great water out the backside

 

[Chanbo]

If the radiator fluid is not changing then the only possible source of steam is the raw water side. Do you have a temperature gauge, or at least a high temp alarm to tell if the engine is overheating? Is there still the normal amount of water coming out the exhaust?

If the radiator fluid is not changing then the only possible source of steam is the raw water side. Do you have a temperature gauge, or at least a high temp alarm to tell if the engine is overheating? Is there still the normal amount of water coming out the exhaust?

Thats what I keep thinking ..this all starts within 1 min of startup with cap on ...

 

[Jim26m]

I'm going to side with the crowd. Sure sounds like a head gasket leak, since you have good raw water flow.

Assume that the engine doesn't (and hasn't!) overheated?

Manual requires retorque after 30 min run-in. Then, retorque anytime engine is stored for an extended period.

My thinking is, you are getting l leakage from the compression stroke that is causing the immediate pressurization, then leaking into the engine on intake stroke. I suspect you aren't noticing the level dropping because you aren't running it long enough.

Guess based on current info, which is still limited.

 

[Jim26m]

When you have it uncapped, there is no pressure on the water jacket to force it in on the intake stroke.

 

[Jim26m]

The fact that it changes when you put the cap on is telling me head gasket and coolant.

Good Luck! Hope you find it soon.

 

[Chanbo]

Have you checked your raw water strainer? Clean if necessary. Open the seacock breifly with the strainer off. Does water flow through rapidly? If not, shove a dowel or wire down the seacock until water flows.

Will check today but cleaned strainer a few weeks ago and plenty of water out the backside

I'm going to side with the crowd. Sure sounds like a head gasket leak, since you have good raw water flow.

Assume that the engine doesn't (and hasn't!) overheated?

Manual requires retorque after 30 min run-in. Then, retorque anytime engine is stored for an extended period.

My thinking is, you are getting l leakage from the compression stroke that is causing the immediate pressurization, then leaking into the engine on intake stroke. I suspect you aren't noticing the level dropping because you aren't running it long enough.

Guess based on current info, which is still limited.

That was my first thought

 

[RitSim]

Harbor freight has a diesel compression tester for $30 +/-. You can consider removing the injectors and compression testing before and after retorquing. You may need additional aluminum (kubota 15221-9402-0) and copper (17011-5362-0)sealing washers to reseat the injectors. The aluminum washer is at the fuel bypass. The copper washer is between the injector and the head.

 

[Kings Gambit]

It’s a matter of flow-through rate. Water in the stainer with the diesel at rest does not mean there is no blockage impeding the flow rate when it is running. Did you perform Canbo’s test (post #16)?

 

[RitSim]

I found that if you have the Kubota part numbers, then you can get parts at the local Kubota dealer and don't have to buy Universal parts. Evidently, the local dealers don't have access to the marine part numbers. My block was a D-950.

 

[Stu Jackson]

My block was a D-950.

That's an M25XP. The M25 is a D850.

Here's the Kubota tractor manual for the M25 series (from our C34 tech wiki Tech Wiki – Catalina 34 International Association):

Kubota Parts Manuals

No marinized parts, use with CAUTION - not all parts fit the "cousin" Universal model engine
• Kubota D850-OEM engine block (M-25 cousin) Parts Manual - Searchable PDF - KKloeber 7/17/17
• Kubota D850 engine block (M-25 cousin) Parts Manual from B6200 tractor manual- Searchable PDF - KKloeber 7/17/17

• Kubota D950-OEM block (M-25XP cousin) Parts Manual- Searchable PDF - KKloeber 7/17/17
• Kubota D950 block (M-25XP cousin) Parts Manual from B7200 tractor manual- Searchable PDF - KKloeber 7/17/17