Volvo Penta MD 2040D losing water

[landonshaw]

I just noticed that my engine is loosing water out of the top of the engine below the radiator caps rom the hole that is designed into the heat exchanger. I thought that when it overheated, the fluid would run out at this spot. Not sure of the name. Now the engine does not run hot. I loose about a gallon into a jug that I have the hose going to. I have a new radiator cap on it, from the end of last year. I am going to change the thermostat, although it is not overheating so don't know if that will do anything. Also will change the impeller. Any thoughts?


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[Lepke]

If you're talking about the expansion tank overflow...

If your coolant completely fills the engine and tank, when warmed up, liquid doesn't compress like air so some coolant will be expelled. If you have an overflow tank, extend the overflow hose to the bottom. That way when the engine cools, it will draw the expelled coolant back into the engine instead of air and keep the engine full. Like your car.

[landonshaw]

Yes, although it never did it before??? And I'm not filling the engine up any more than before. It did not have an expansion tank on it. I had the plastic container there so if it ever did overheat, I wouldn't be cleaning it out of the bilge.


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[Neilhoh]

Had same issue with newly purchased yacht with 2040D, no overheating alarm. And, at the same time noticed, innocuous enough, steam coming from the exhaust - not smoke. Googled it and popular opinion was that it was getting hot, perhaps not enough to set alarm off.
- Opened water pump">raw water pump - 2 blades gone from impeller.
- pulled out heat exchanger - about 1/3 clogged, soaked in vinigar and reamed out with a plastic ... knitting needle it might have been.
- checked exhaust ebow - almost closed up with rust and salt.
Amazing that the thing was cooking.

All jobs pretty easy and easy access in a Bene 393.

Apparently these engines run quite cool from what I have read, so even though the alarm might no go off, and it might not seem hot, the temperature could be abnormally high.

In any event I was sure glad I went through the entire cooling system.

Ever since, the raw water pup has leaked a little and I have a refurb kit coming this week. Maybe now that there is less back pressure the bearings and seals are out of alignment.

[landonshaw]

The impeller was fine. I just replaced it. Part of my maintenance each year or 100 hours. Attached an expansion tank of sorts. Clear jug to see if the volume is changing. So far all is running well. And yes I have always found it to run cool. Thank you for confirming. I heading from Grenada to Anguilla then back for a 6 week sail and hopeffully little motoring. Should be a good test for the engine when I do have to motor.

[DougR]

If you have pushed a gallon of water out of the expansion tank overflow, and levels still seem normal and the engine doesn't overheat, it's likely that you are getting salt water intruding into the freshwater/antifreeze side of the cooling system.

On the 2040 engine the salt water side of the system is isolated from the freshwater side of the system by the front most and rear most hose clamps on the rubber heat exchanger end caps. There are two hose clamps on each end of the heat exchanger. The inner most clamp on each end seals the expansion tank and prevents antifreeze from escaping from the engine. The outermost clamp seals the salt water side from the freshwater side. If one or both of the outermost clamps are loose, the possibility exists that sea water could make its way from the sea water side to the freshwater side filling the system completely and allowing no room for expansion. Then when the engine began to warm up the building pressure would force water out the overflow.

As mentioned by another poster here, blockage in the heat exchanger tube bundle or exhaust elbow can cause higher than normal pressures in the seawater side of the system, and could contribute to the crossover.

I suggest removing the heat exchanger end caps and cleaning the heat exchanger tube bundle. While you are at it, check the exhaust elbow for water and exhaust flow restriction. Then when you reinstall everything be sure the hose clamps are positioned correctly and tightened securely, but not overnight.

DougR

[landonshaw]

thank you, I will verify. Dave

[DougR]

Forgot to mention that when you remove the rubber end caps from the HE bundle you will also loose antifreeze down to the level of the bottom of the end cap.....so you might want to drain down the coolant first so it doesn't go all over the place.
DougR