Getset discharging coolant through overflow hose.

[Franklin]

I have a Phasor 3.5 kw diesel genset that I've used through the past 12 years...rarely, but the past 2 years a lot more (like 30 hours a month during the summer months). The past year I've had a coolant leak but felt it was just the cap which is partly broken. I replaced the cap and at first that helped. I could go about 5 hours before it needed water. Now I am losing half the water after just an hour or two at low load.

I put a glass jar to capture the overflow (it never had a overflow tank) and it seems most of what is missing goes into the jar. I think it is because of combustion gas entering the cooling system and displacing the coolant causing it to overflow, but how? The two thoughts that come to my mind are a cracked cylinder or a busted head gasket. The busted head gasket sound plausible due to it getting worse in time, but I always thought that put water in the crankcase.

What is your best guess?

 

[kloudie1]

Is it overheating? does it have a temperature gauge? Is the seat for the cap clean and straight?.. Usually a cracked head would leak coolant to crankcase but in some cases, it can leak gas to coolant.. in a one cylinder engine, that would make it almost impossible to start.... a crack in the block would almost always leak to crankcase.. If you are sure of the sealing condition of the cap and seating surfaces, ya might consider re-torqueing the head to see if that changes things.. if it does, a head gasket or cylinder head leak would be a prime suspect..

 

[Franklin]

If I run it long enough, it will shutdown due to the temperature kill switch. No gauge.

I think the new cap is fitting pretty good.

 

[Amos Cape]

After checking the above. I would try to pickle your fresh water system with Barnacle Buster. You could have a blockage in the system.

 

[kloudie1]

Hmmmmm.. sounds like it may be spitting water out from incipient overheating.. I'd suspect the sea water side (if you've been diligent about coolant/antifreeze); seawater pump impeller or drive belt or restricted flow to/from.. or a slightly loose hose connection allowing air into the seawater or restricted flow into thee exhaust mixer..

 

[Franklin]

After cleaning the connection of the heat exchanger and the cap, it doesn't put much out, so I am thinking it is not the head gasket or any of that stuff, just a bad seal on the cap and maybe a bit too much junk in the exchanger. I will take that off when I get to Fiji and clean it out. So glad it isn't anything that requires parts because it is hard to get parts for this genset out here.

I know the raw water pump is working fine.

 

[Rich Stidger]

Years ago the pressure cap on my Volvo auxiliary began leaking. It took me 2 more caps before I was able to stop the pressure leak. I cleaned the seat for the cap gasket and I remember not seeing anything obvious. And the original cap held pressure just fine until it didn't. Just sayin....

However, I just remembered an easy test for a defective head gasket where the failure is between the cylinder and the cooling passages. While the engine is warming up and running, remove the pressure cap. If there is a head gasket leak, you should see continuous bubbles being expelled from the cap. Of course the gasket could leak only at maximum temperature (so you might not see bubbles during warm-up), but this is an easy test to perform that could give a good indication of a leak.

 

[thinwater]

You can also expect a sharp drop in pH if it is exhaust. If the coolant is turning rusty that is another clue.