Heat Exchanger Leak

[ken_23434]

I have noticed that my engine has been losing coolant, but there are no external leaks. My engine is missing the expansion bottle, so initially, I thought it was normal expansion and contraction without the makeup from the expansion bottle.

I decided to do a pressure check just to make sure everything was OK. I can easily build pressure (went to 15psi) but it will drop VERY slowly. Maybe half a pound a minute. While sitting there waiting to see how fast the pressure would blead down and looking for any water dripping in the bilge, I noticed water coming from the outdrive.

I am pretty sure the only way for that to happen is a leak in the heat exhanger. By the way, this is a 3 liter Mercruiser with the FWC system that cools the block only.

My question is: Is there a way to plug an individual tube in the heat exchanger? Or is there some way to access the tube to make a repair?

 

[jerryjerry05]

Re: Heat Exchanger Leak

Did you drain the coolant when you did the test?If so get a stethascope. Pressurize the system.Use the stethascope and put it on the heat exchanger. They make stethascopes for mechanics.If only the block is cooled by antifreeze then it should be easy to find the leak.
Take it to a radiator shop they should be able to fix it.
Hampton roads sounds like a salt water boat.These have sacrificial anodes in the system.If they don't get replaced the tubes in the exchanger can rot away.If would check them at the same time.Most people don't know that they are in the system. If you want to know how to guard against corrosion just ask.Jerry

 

[DJ]

Re: Heat Exchanger Leak

A lot depends on how complete your system is.

Engine only?

Engine and manifolds?

If it is the latter, I would suspect your risers and manifolds.

 

[ken_23434]

Re: Heat Exchanger Leak

Thanks, Jerry. I did not know sacrificial anodes were in the cooling system. It makes sense that they would use them, though. This is my first boat and in the condition I recieved it, I have learned A LOT.

The system cools the block only. That's why I am pretty certain that the leak has to be in the heat exchanger. That's the only place the antifreeze has a chance to come close to the sea water side.

I was hoping there was a way to pull out a tube to fix it or maybe a gasket that could isolate the two sides, etc...

 

[Don S]

Re: Heat Exchanger Leak

Just remove the heat exchanger from the boat. Remove the end caps and block one port of the coolant passages, and pressureize the other coolant passage. Put the heat exchanger (while pressureized) into a tub of water. If it bubbles, it leaks.

 

[enn858]

Re: Heat Exchanger Leak

The OEM heat exchanger for the 3.0 has NO sacrificial anodes i have a 3.0 with the original Mercruiser heatexchanger and there is for shure no sacrificial anodes anywhere in the heat exchanger - i have been thinking about installing some - but there is no space for it inside the exchanger

 

[jerryjerry05]

Re: Heat Exchanger Leak

Is there a bottom drain plug or two? If there is,then the anode can go in the drain plug.The second hole probably was the anode.Jerry