Steam Woes-Replacing a Fuel Cooler on a Cummins QSM 11.

Let me start by saying that this is not an easy task BUT it does not require much expertise. This is more of a physical challenge with great rewards. The background for this project starts with a trip from St. Augustine to Bimini. On the trip back I would notice little puffs of white coming from the exhaust. It was not a great amount and it came more from the port than star. About 6 months later the puffs became bellowing steam clouds at cruise. It did not steam at low RPMs. The temperature of the port was also at 175 F which was 3 degrees higher than the star engine. It was time to fix something.

This was the start of my investigation into the origin of the white puffs. I am very fortunate as virtually every maintenance record for this boat was handed over when purchased. Not only that, I can speak to both the original owner as well as the second owner. Remember, this boat is a 1986 Hatteras 52C which was repowered in 2009 with these Cummins Engines.

I started going through all work previously completed as well as the work I had done. I also noted maintenance and what was and was not covered annually. One thing stuck out- I did not have a fluid exit on the engine seawater line therefore the barnacle buster flush stopped right before the water pump and did not go through the fuel cooler. I also noted that these fuel coolers had no notes for work or maintenance since 2009 and they looked it.

I won’t use this article to get into the need to have a fuel cooler or the possibility of removing it. It is a standard item for these engines and you can find a multitude of post regarding this. I will say that the water I am in is very warm most of the year so I was keeping mine.

So what is it. Exactly what the name implies. It is one of several heat exchangers on the boat. This one cools the fuel before it returns to the tank. There is one for each engine. It is placed between the seacock and the water pump. It is also UNDER the engine. It is also important to note that they serve as a filter for the incoming water on my setup. My seawater flows from exterior rectangular scoop strainer to seacock to fuel cooler to water pump to engine.

Photo showing the portside location under the engine. Fuel lines have been removed.

There are two approaches you can take to these coolers. They can be removed, pressure tested, acid cleaned and then re-installed or they can be replaced. Good luck finding a shop that does this in your area. Due to the neglect and age, as well as what I found, I wanted to have no worries with these for a long time so they were replaced.

Step 1-Disconnect the fuel lines. Make sure you have some method for catching the fuel which will come out of these lines once detached. It should not be too much.

Step 2-Disconnect the electrical wiring to the Starter. I covered these with our covers we sell here. I would clean and cover them to prevent damage.

Step 3-Relocate any wiring that impedes removal of the starter. Be easy with this stuff. I gently moved and tied the wiring at a higher location.

This is a heavy starter and a rough process.  Move these fragile wires so you don't create another project.

Step 4-Remove the starter. You will need socket extensions for this as well as wrenches. It is not that hard so don’t back out now. Use this as a time to inspect the teeth of the starter as well as remove rust and paint.

NOTE: It seems like you are removing a bunch of stuff and it is just taking more time. This is all done in an effort to let you be able to not only remove the fuel cooler but to wrap you arms around the hose and work it off. Its been on there for some time and it is probably double wire reinforced and molded to the cooler lip.

Here is the opening which was created once the starter has been removed.  Note that you can not remove the oil pan on one side or the steel rail on the other.  this is all you have as far as space goes.

Step 5- Disconnect the seawater hose. Shut the seacock first. Make sure that your seacocks work if you are in the water. This is a good time to inspect all of your double clamps and replace.

Step 6-Remove the Fuel Cooler bracket. This is a process consist of multiple steps. The bolts to the engine and the clamps to the water pump must be removed. then move the whole assembly into the starter hole you created and work it out. Then remove the bracket from the fuel cooler once the assembly is out.

Working the assembly out.

Removing the Fuel Cooler.  These bolts are not accessible until it is out as shown.  It is definitely a good idea to slow down and paint these bolts and bracket once they are reinstalled.

Step 7-Wire brush and paint everything you can. I added this because I don’t plan on accessing this area for a while.

Step 8-Replace the heat exchanger on the bracket. When I compared the two exchangers it was amazing the amount of blockage that was present. It was also amazing to note that there was fishing line and other junk in there. Note the mineral buildup. This could be removed with a barnacle buster flush if I had a way to do this.

The original vs the new replacement.

I would guess that there was 10% availability on the tubes.

The new Fuel Cooler with 100% availability.

Step 9-Reverse the steps and put everything back. I replaced the small section of hose between the water pump and the fuel cooler. I inspected all clamps, cleaned or replaced.

This was a very physical job in a small cramped space. I can not imagine what a Cummins Mechanic would charge for this work. It is NOT mentally challenging and did not require and special tools. The operating temps at cruise of both engines dropped from 170F+ to a constant 164 F. The original coolers made it 15 years. The cost to do this work, besides labor, is as follows:

Mr. Cool Cummins Fuel Coolers (2)($600 each)-$1200.00

Spray Paint-$5.00

Hose (2.5”)-$50.00 (bought extra)

Clamps (4)-$48.00

Steel rail was cleaned and painted following this install.

Tight Lines and GOOD LUCK!

Scott