Cooling water leak - heat exchanger?

[suiramor]

I am trying to figure out where my fresh water is leaking from the cooling system. I lost about a half a gl of water after using the engine for +-3h + a few days absence (I only noticed the loss after that). I added some UV dye to see whether that will show a leak anywhere on the system - nothing seems to be leaking. Is it possible that the leak is in the heat exchanger (this is on a Westerbeke 65B) and the fresh water goes out to the ocean? (using UV light on the exhaust water seems rather hopeless). Is there a way to check it?

[Khaos13]

I simply put a loop of hose on the seawater in/out ports and put an air fitting in the zinc port. Stick the whole thing in a bucket of water and add VERY LITTLE air. Look for bubbles.

[Ryban]

Originally Posted by Khaos13

I simply put a loop of hose on the seawater in/out ports and put an air fitting in the zinc port. Stick the whole thing in a bucket of water and add VERY LITTLE air. Look for bubbles.

Can you clarify this setup a little. Are you injecting air into the coolant side of the system and looking for air bubbles on the raw water side, or the opposite? Is the engine running in this configuration?

I also have a leak that I have not been able to trace down yet. I pressurized my coolant system to 12PSI and there was nearly no drop in 2 hours, and only a drop to 9PSI after 2 days. I'm guessing in my case it's either the radiator cap, or manifesting only when the engine is warm/vibrating.

[Lepke]

If the engine is running fine, then you probably don't have a head gasket leak. That type of leak usually puts combustion gas into the coolant and that usually forces coolant out of the pressure cap. You will also see bubbles in the coolant. You can get a test for combustion gas in the coolant at most auto parts stores.
The most common place coolant escapes is in crossing to the salt water side in the heat exchanger and out the discharge. You can have the heat exchanger pressure tested at a radiator shop.
Clearances change in an engine when it warms. A small leak in a heat exchanger may not show in a cold engine. The only other place coolant can go is in the oil. And you'd probably already noticed a half gallon of water in the oil.

[Khaos13]

With my simple test I have both end caps installed and a loop of hose between (essentially blocking) the sea water intakes. I remove the zinc and installed a 1/4 NPT male air fitting. Connect the air line and submerge the whole thing in a 5 gallon bucket. If there is a leak in the tube stack, bubbles will come out of the coolant inlet / outlet ports. Too much air pressure and the end cap gaskets or the hose clamps will leak. Lepke is correct, this is a cold test and does not allow for changes that can occur at operating temps.

[more]

Originally Posted by suiramor

I am trying to figure out where my fresh water is leaking from the cooling system. I lost about a half a gl of water after using the engine for +-3h + a few days absence (I only noticed the loss after that). I added some UV dye to see whether that will show a leak anywhere on the system - nothing seems to be leaking. Is it possible that the leak is in the heat exchanger (this is on a Westerbeke 65B) and the fresh water goes out to the ocean? (using UV light on the exhaust water seems rather hopeless). Is there a way to check it?

this is easy for check. remove heat exschanger from engine. in service use rubber plug for this heat eschanger. pressure 2-3 bar and sumerge in water. folow repair manual. i know for volvo penta, you visit your engine dealer

[Khaos13]

I'm not sure what your exhaust manifold looks like, but the one on My Westerbeke W21A is a good possibility for coolant loss. The coolant surrounds the exhaust manifold and only the end cap gaskets keep the 2 from mixing. Coolant can leak into the exhaust chamber and enter the cylinders in a worst case scenario. This was common on this old style manifold. Definitely could be heat related too as the sealing surfaces are so narrow.