FL 120 Heat Exchanger

[Mambo42]

I was changing the zincs on the heat exchanger, which (as far as I know) only are on the top of the heat exchanger. Since I wanted to drain the heat exchanger as well to be able to open it in order to take a look at the condition of the heat exchanger, I took away one of the bolts on the bottom, but no water or cooling liquid came out. What did come out was this bolt and it looks like there used to be a zinc in there as well. However, since no liquid (water or cooling liquid) I am wondering what the purpose of a zinc would be.

Anyone has an idea what this bolt is for ? It is on the bottom of the heat exchanger and it is the bolt closest to the left side of the heat exchanger. I have searched for a schematic depiction of this heat exchanger, but cannot find it anywhere. The heat exchanger was taken out last year for a pressure test, then the zincs were replaced, but not by me,

 

[Marco Flamingo]

That location is where the pencil zinc is on my Lehman. The first time I removed it, there was no pencil zinc in the fitting. A little water came out, so I put it back in and went off to the store for a new zinc. When I returned and removed it again, there was a zinc. Apparently I had managed to "rethread" the zinc and remove it. It was corroded enough so that I replaced it. I noted the size and ordered about 5 off the internet (1/3 the price of my local WM).

I added a little o-ring that fit tight over the zinc threads. That way, the o-ring created a water-tight seal and the threads weren't subject to corrosion. Seemed like a better idea than trying to put goop on the threads and maybe increasing electrical resistance.

While replacing the zinc I noticed that water would drip out and then slowly increase. I believe that my heat exchanger is at or just below my boat's waterline. Maybe it is possible to have the heat exchanger just above the waterline such that there is no syphon action and the heat exchanger appears dry?

 

[av8r]

It looks like the zinc rod is still in the heat exchanger, when you unscrewed the brass base from the HX it also unscrewed the zinc from the base. You’ll be able to see it when you remove the end cap and can clean it out. The HX is probably still full of water, be ready when you remove the cap.

 

[SteveK]

Agreed, if no water comes out the remains of the zinc are plugging the hole.

 

[Mambo42]

I had a remain of the zinc on top of the heat exchanger, that was indeed still stuck. But the bottom one had salt built up on the remain part of the zinc, so not sure there was a lot left of that zinc. Only problem is that i don't know what the bottom 'zinc' was for ? Is there a double zinc in this heat exchanger ?

 

[Nepidae]

The first thing you should always do with a Ford Lehman question is call Brian at American Diesel.

His dad built the engine so he has knowledge that no one else has plus he also has parts for the engines.

AmericanDieselCorp.com for the number.

 

[av8r47d]

+1 to Nepidae. Call American diesel. He answers the phone and will save you a lot of trial and error.

I just got off the phone with him discussing heat exchangers, there are two plugs on the bottom. The plug closest to the end is the raw water drain. The center drain plug is for the engine coolant side. The zinc, I assume is to prevent corrosion on the coils inside the exchanger where they are exposed to raw water.