Heat exchanger questions.

[mherrcat]

I am going to pull the heat exchanger on my M-18 engine this weekend to inspect and clean. Will a mild muratic acid wash necessitate repainting? Also, I believe there is a rubber gasket in one or both ends; can these be reused or should they be replaced? Where should I look for them?

The h/e looks like it is powder coated, but not certain.

 

[Mort Fligelman]

Heat Exchanger

I had my heat exchanger gone over in Florida last April.

Everyone I talked to said that it should be taken to an auto radiator shop and "Boiled Out".....a term I had not heard in many years......but when auto radiators were Brass and Copper that is what was done.

I was advised to replace the end caps, and the large rubber washers, along with the small fibre washers.....and of course the pencil zinc.

This is what is called a complete refurbish, and included painting.....with the parts it came to just over $100.00.

With salt water going through it and the possibility of electrolisis I felt it was well worth the investment.

The parts are available at any chandlery that carries Sen Dur exchangers.

 

[joe-fran]

Heat exchanger

Mark
I pulled my H/E last winter and had it dipped at a local radiator shop. (There used to be a shop on every corner many years ago but there are few left today) I pulled out the zinc and opened up the one end ahead of time for my own inspection. The zinc was all but gone and the gasket pretty old but no sign of an junk inside the H/E to obstruct the water flow. I purchased a new zinc and gasket at a local marine store. I think the gasket was a couple of dollars. anway for about $25.00 (cash) the radiator shop dipped it for a couple of days and installed the new zink and end gasket. Mine was not painted or power coated so I did spray paint it before going back in.

My recomendation is NOT to reuse any gaskets. It was obvious that the PO made a home made gasket from a thin rubber (inner tube maybe) gasket. To my way of thinking, that's just not worth a couple of buck savings. (and I am just as cheap as the next sailor)

Joe E-28

 

[mherrcat]

I pulled the H/E Sunday night; pretty easy except for the amount of space I had to work in.

There was not as much corrosion as I feared; in fact there was very little. What I thought was corrosion on the raw water outlet was actually some teflon tape on the threads of the nipple. There were some remnants of zincs in one end that I had to skillfully extract as that end does not have a removeable cap.

I removed the one end cap and all the small tubes were clear. I mixed a 50/50 muratic acid solution and soaked the H/E for about 20 to 30 minutes, circulating the solution every few minutes. This plus running a .177 caliber pistol cleaning brush through the tubes cleaned it up very well. (Do that after washing the acid off with water or it will eat up the brush bristles very quickly!)

I ordered a couple of gaskets from Torresen. From the pics on their website they look like they might just be thin rubber washers that I could get at a hardware store...we'll see.

Some of the original paint had worn off where the H/E sits on the mounting bracket so I am going to strip the rest of it off and repaint with some high-temp engine enamel.

 

[Frank Langer]

Hi Mark,

Thanks for your post about cleaning your heat exchanger. Do you know when it was last cleaned or replaced? My reason for asking is that mine was replaced about 3 years ago (300 engine hours) and I have been considering taking it apart to clean it this fall. But if yours has been going for alot longer and isn't showing much corrosion, maybe mine doesn't need it yet.

Any thoughts or advice would be much appreciated.

Frank
1984 E30+

 

[mherrcat]

I don't know when the H/E was replaced, but it looked pretty much new in January 2008 when I bought into the boat. I started out with a partner in the boat; he bought it in June 2007. So I imagine the H/E was replaced sometime in early 2007.

When I first asked my ex-partner about changing the zinc he said, "Oh, they don't use them anymore." (Idiot.) Not knowing any better at the time I never checked. Later, when I did check in about November 2008, there was no zinc left at all; it had probably been without one for 17 months. (Maybe longer, since the nut on the end of the zinc had been painted when the H/E was originally painted!)

It really was a simple process to remove the H/E so I would recommend doing it; at three years old it seems like it would be due. I drained all the coolant from the engine first to avoid as much mess as possible. Also don't forget to shut off your raw water intake valve. The nuts on a couple of the hose clamps were a little tricky to get to but overall I think it took me about an hour to get it off, including draining the coolant.

 

[mherrcat]

Is there a torque spec for the end cap bolt on the heat exchanger? Or do I just tighten it enough to compress the rubber gasket?

I finally got the H/E painted and it goes back in tomorrow along with some new hoses, if WM has the right sizes.

Here's a couple of pics; primered and painted. I took these with my iPhone, I guess that's why the H/E looks radioactive...

 

[Frank Langer]

I cleaned ours out earlier this week. When I undid the nut at the end, it was only snug, not really tight. Yet it had indented the rubber washer a bit. So when I reinstalled it, I snugged it up rather than tighten it hard. After running the engine for awhile, there is no sign of a leak. With the end cap sitting on the rubber gasket, I would think that overtightening it would flatten the rubber more than one would want.

I didn't repaint mine, so it doesn't look as good as yours...

Frank

 

[mherrcat]

Thanks for the info. That's about what I figured.

I almost didn't repaint either, but the mounting bracket was rusty and had worn through the paint on the bottom so I figured as long as I had it out. I used some high-temp engine enamel that has to be cured for an hour in a 200 degree oven. We'll see how well it holds up.

I am going to clean up the bracket as best I can without removing it and maybe put a rubber sleeve around the H/E where it sits on the bracket to try to keep it from wearing through again.

 

[mherrcat]

Finally, here's a pic of the refurbished H/E installed. I used some sheet rubber cut to fit between the bottom of the H/E and the bracket and under the hose clamps to try to eliminate wear from vibration. I noticed that some of the paint had worn away when I originally removed the H/E.

No leaks so far...