Cummins Zincs Replacement

[Aerobaticflyer]

After a lot of searching here I have found a lot of good info on changing engine zincs but not specifically the info I need.

So can any one tell me how many zincs are on my engines and a bit of detail as to their location? I know of the two (one upper and one lower) on my heat exchangers. Pictures for dummies would not insult me! :smt001

Engines are Cummins QSB 380's 5.9's in my 2005 390DA.

Thanks!

 

[alnav]

I believe all the QSB-series engines are the same in this regard. There should only be 3 engine zincs, one on the heat exchanger and two on the aftercooler, one at the top and one at the bottom. They are E2 Zincs, 1/2 NPT, 5/8" diameter, 2" long. You can save some money if you buy just the anode and re-use the base, although I would get a couple of complete ones in case you need them. BoatZincs.com is where I get mine.

 

[alnav]

Just re-read your original post and should have pointed out that you may be confusing the aftercooler with the heat exchanger. The aftercooler zincs are horizontal and very noticeable, the one on the heat exchanger is on the underside at the front and is placed vertically.

 

[trit21]

Here you go. Should be very clear from this pdf file.

http://sbmar.com/Maintenance/PDF/QSB-6BTA-Zinc-Location.pdf

 

[Aerobaticflyer]

Thanks Al & Tom,

Looks pretty straight forword.....assuming nothing comes apart and drops in the after cooler or heat exchanger I should be OK.....worth a try.

No thread tape or dope I assume to keep the anode functioning properly? I guess I should get some water from the lower zinc opening in the after cooler and the one on the heat exchanger? Any priming or bleeding necessary?

Sorry for the elementary questions...still pretty new to the diesel world.

Thanks again.

 

[alnav]

No thread tape or dope I assume to keep the anode functioning properly? I guess I should get some water from the lower zinc opening in the after cooler and the one on the heat exchanger? Any priming or bleeding necessary?

Correct, put nothing on the threads. You will get some drainage from the lower aftercooler and heat exchanger openings. I'm not sure it makes a difference but I would close the seacocks before I started as well.

 

[timjet]

You may also want to consider a fresh water flush. Easy to install and will extend the life of your zinc's & engine.

 

[Aerobaticflyer]

Can you just refill the coolant overflow resevoir to replace the coolant you lose when replacing the heat exchanger zinc? I assume you'll lose quite a bit if the exchanger is full of coolant.

 

[osd9]

You will not lose any coolant . Zincs are only on the raw water side....no zincs on the closed cooling side. That's why it was recommended that you close your seacocks before you start the process.....but don't forget to reopen them.

I don't have any first hand knowledge changing zincs on your specific application, but closing the seacock may not be necessary if the water line is below any zincs being changed. I would leave it open and try....if water comes out of the hole, then close the seacock. If you don't have to close the seacock to change the zincs, your are better off.....that way you won't forget to reopen them.

 

[alnav]

Can you just refill the coolant overflow resevoir to replace the coolant you lose when replacing the heat exchanger zinc? I assume you'll lose quite a bit if the exchanger is full of coolant.

All the zincs are in the seawater side of the cooling system so no antifreeze should be lost. There is of course, antifreeeze flowing through the heat exchanger but it's in a loop that you won't open as part of this procedure. Make sure the seacocks are closed before you get started.

 

[Aerobaticflyer]

Guess I could have waited a little longer! ;-)

 

[LMBoat]

Guys,

I have a 6CTA and have found 3 per engine <2 in the intercooler, 1 in the heat exchanger. Did I miss any?

 

[Asureyez]

On the 6CTA, there are THREE and THREE only pencil zincs, same as the 6BTA. Two (2) are on the AFTERCOOLER, top and bottom, and one is on the forward (engine forward) heat exchanger, threaded up from the bottom as shown in the photos above.

For newbies, when pulling these old zincs, the brass may separate from the threaded stub of the old zinc leaving it hanging in the port. Should this happen you will need long thin needle nose pliers to grasp the threads and wiggle the stub out.

If you have lost the zinc in the housing, it will need to be removed. Remove the end cap and remove the lost zinc stub and other debris and re install the end cap, the old gasket will probably need to be replaced. Clean the gasket seats and the threads on the bolts while you're at it and torque to spec. If you see a lot of white scale build up around the tubes, don't pick at it and bugger up the solder joins, just remove the chunks and reassemble. When done, prepare to do a Acid (Barnacle Buster) flush of the raw water side of the system. But that is covered here elsewhere.

When replacing the zinc on the HE, you'll want to also remove the end cap and remove debris and inspect the tubes, a new rubber gasket is often not required, just line it up as when removed, the how will be obvious.

NOTE: Old zincs will tend to make a flaking mess in the ER during removal, I hold a small bucket under the work to catch the metal debris as I get the old stuff out.

Now about the pencil zincs. You need not always buy new brass, you can install new pencils in to the old brass. Here is how. Unscrew the old zinc from the brass, and inspect the brass threads, clean as indicated. Then by hand screw in the new pencil zinc to the brass until snug, BUT don't stop there. With a small hammer or flat metal wrench, TAP the end of the zinc to seat the threads and again hand tighten. Too much twisting will break off the zinc from the threaded end, (THATS BAD)!

The brass is NPT so it will seat water tight when snugged down.

I run in salt water and have a good bonding system, but electrolysis is a huge enemy. I check/change my zincs every six months. As a economy effort, I will swap the zinc at the top of the AFTERCOOLER which rarely shows any sign of erosion to the bottom. On my rig the only zinc that seems to ever erode away is the one at the bottom of the AFTERCOOLER. The Zinc in the HE sometimes can go 125 hours or a year.

From experience, the zinc at the bottom of the AFTERCOOLER is the most active and should be looked after closely especially if you are on hot docks or do a lot of transient cruising.

 

[osd9]

......From experience, the zinc at the bottom of the AFTERCOOLER is the most active and should be looked after closely especially if you are on hot docks or do a lot of transient cruising.

It may be that the seawater line is high enough that that zinc is constantly sitting in the 'electrolyte'. If you have the zinc plug out, and openend the thru hull, and water comes out, that would answer that question.