Yanmar heat exchanger

[R&B]

I have a yanmar 3gm30f on board and what I have noticed is that I have been loosing some coolant in the heat exchange tank...I did find some small leaks in the hosing an changed them out (thought I had the problem solved)but it didnt fix the lossof the coolant all that much...I found out there could be two causes..1 being a leak in the head gasket and 2 a mixing of the coolant and the raw water in the exchanger....since the easier job seems tobe the mixing of the raw and fresh water so I think I need to start there..It looks easy enough to remove the whole unit but who could do the job of checking for leaks in the unit itself.....and if a leak does existist what kind of place could fix it? I was thinking a auto radiator shop...any suggestions would be greatly appreciated....

[delmarrey]

I don't know about Yanmar but most marine exhausts have a replaceble core in the heat exchangers. Take a look at your manuals. You may be able to just buy a new core and seals and be right back in business.

Repairing a heat excgr would probably be more costly then just a core replacement, unless you have a fairly large motor (500 hp+).

[cal40john]

First of all get a manual.

Rent a radiator pressure tester, about $16 around here for a day.

The Chiltons ( I need to go to the boat to verify.) or Yanmar manual (definitely) will have the steps and pressures to follow.

If you verify that the leak is in the heat exchanger, the end caps on the manifold/exchanger come off and the tube set comes out, but you will already know that since you now have a manual.

Haven't had to do any of this yet, my leaks were obviously loose hoses that coolant could be seen coming out with the engine running, but I was looking at what the next steps were.

John

[Boracay]

At the moment I am going over my old Ford and replacing all the old rusty hose clamps. I have found coolant leaks at a few of the hose/pipe joins.
While I do not recommend the method, covering the engine with fine sawdust does show up the leaks.
I just don't trust old hose clamps.

[delmarrey]

Go here.......... Populaire scheepsmotoren, Scheepsmotorensite, Marine-engines

There is a pdf. manual but I didn't see anything on a heat exchanger with just a quick run thru, have to run. But it might be some good info to have for starters.......................................... ..............._/)

[NoTies]

Some models of Yanmar (can't remember which but nevermonday could help) had non removeable cores in the heat exchanger and they also had a problem with tubes leaking due to electrolysis. They were basically a throw away item and the problems with them seemed to be that they weren't electrically bonded to the engine (they were supported by rubber hosing and had no metal brackets to the engine block). If this is your case make sure you bond the cooler to the block after repair.

[gonesail]

i'm pretty sure that if you have a leak in the heat exchanger you will then see an increase in coolant in your fresh water overflow tank.

[never monday]

Gm series has a hard mounted cooler in the exhaust manifold/coolant tank.
I remember some QM's that had aftermarket fresh water cooling systems.

I'd first rent a pressure tester and find the leak before tearing things apart.
Also, do you have the expansion tank hooked up? is it holding coolant? When the engine gets to temp, some coolant be lost without it.

Pat

[cal40john]

Originally Posted by delmarrey

Go here.......... Populaire scheepsmotoren, Scheepsmotorensite, Marine-engines

There is a pdf. manual but I didn't see anything on a heat exchanger with just a quick run thru, have to run. But it might be some good info to have for starters.......................................... ..............._/)

That's where it is. Well that was more helpful than I was. It's the GM-HM workshop manual, 60 MB. I really need to start saving where I got stuff from as well as saving it. It's Chapter 8. Near the beginning of the chapter are the exploded diagrams of the heat exchanger, near the end of the chapter is the "Freshwater Cooling System Maintenance", first subsection Pressure Testing.

Originally Posted by gonesail

i'm pretty sure that if you have a leak in the heat exchanger you will then see an increase in coolant in your fresh water overflow tank.

I thought the same thing, or at least that you wouldn't see a loss of coolant. A friend with a Perkins had a leak that he couldn't find, a mechanic found the leak in the heat exchanger, problem solved. My theory as to why you wouldn't see a loss of coolant was even though the freshwater side gets pressurized and would force coolant out through the leak into the saltwater side, is when the engine cooled down, it would pull saltwater into the freshwater side as the pressure decreased. Hypothesis crushed by real world example.

John

[AnchorageGuy]

A leak in the heat exchanger will cause you to loose coolant. A easy check of the head gasket is first check the oil and look for a milky color. Next remove the injectors and turn the engine over. Look for water being forced out. Do the leak down test on the heat exchanger and if it fails to hold pressure replace it, don't try to fix it. This is not an automobile and it operates in a very hostile environment for a combustion engine.

[R&B]

Thanks Gang as always your advice is greatly appreciated!!!