preventive maintenance on Cummins engines

[jim rosenthal]

One of the mechanics from T&S Marine drove up today and we spent a couple of hours pulling the aftercooler cores and greasing them. I thought I would pass along the rationale for doing this on engines with low hours:

The aftercoolers are bronze bundles; the seawater from the raw water pump runs through them before it goes through anything else, and the charge air from the turbo swirls around the bronze bundles before it goes into the intake manifold. The aftercooler housing is aluminum, no doubt done to save weight. There are two large pencil zincs, E5 size, one at the top and one at the bottom. The whole assembly is kind of diamond-shaped and is on the port side of the engine about two-thirds of the way back. At each end of the aftercooler bundle is a rubber O-ring that keeps the seawater out of the incoming air path.

Although Cummins doesn't make a point of telling you this, the bronze aftercooler bundle can weld itself to the aluminum housing by corrosion, making it very difficult to get out and clean. Tony Athens says something about this on the Boatdiesel.com web site. Evidently past a certain point the aftercooler bundle is so stuck in there that it can't be gotten out and the engine owner ends up buying a whole new aftercooler.

The solution to this is what we did today: take the aftercooler apart (drain it and take off the end caps), clean everything up with emery paper and put it all back together and grease the ends and all the mating surfaces before putting in new O-rings. (Also new zincs, including the one on the heat exchanger) This needs to be done every couple of hundred hours, which for me will be a long time. The problem in pleasure boat use is that they sit around for a long time with salt water in them and inevitably corrosion begins. We're all familiar with that.

The aftercoolers themselves were clean- the tubes aren't clogged or fouled. The top zincs were nearly intact (the water level falls below them when the engine isn't running). The bottom zincs were gone. The aftercooler bundle is a snug fit- you use a wood block and a mallet to tap it out part way so that you can clean the end, then you tap it in the other direction to do the other end. On one engine, we had to take the assembly off; on the other, we were able to leave the unit attached to the engine and just tap it up and down to get the cleaning done etc.

From what I can gather, Cummins B and C diesels are pretty low-maintenance items. This is one of the things that do need to be done in order to keep them healthy and avoid big expenses later on. Next time we do this, which will hopefully be a while, we will do the heat exchangers as well.

Incidentally, on the first engine, I shut the seawater intake off. On the second one, I didn't bother. At least in my installation, it didn't make a difference, but I wouldn't leave the system open and be away from the boat.

[34Hatt]

Maybe he read Tony's Tips.
http://www.sbmar.com/Maintenance/Aftercooler_Maintenance.cfm

Now for the rest of your B motor.

Get your self two of Tony's Seamax pump ASAP get rid of the crap Sherwood.
Also do the Idler pulley update it simple and cheap. The new breather assembly is also great keeps your engine room cleaner.
I have done everything Tony recommends and been very please with all of it. It all makes sense.

I know your motors are new but I have been telling a friend with a mainship pilot to change his pump he did not do it. Last year with a little over 200 hrs it went called in Cummins and $1,800 later he got another Sherwood pump. I just replaced my port pump last night took off a perfect working Sherwood and put the Seamax on. Did not want to do it in August :D

[Maynard Rupp]

Sherwood pumps are made near my Detroit home. They are pure junk, in my opinion. Their impellers never last 2 years and the stupid woodruff key makes changing that stupid impeller a nightmare. Of course our Crusaders have Sherwood pumps.:(

[34Hatt]

Sherwood pumps are made near my Detroit home. They are pure junk, in my opinion. Their impellers never last 2 years and the stupid woodruff key makes changing that stupid impeller a nightmare. Of course our Crusaders have Sherwood pumps.:(

Yup the key are junk AND A PINTA plus know to shear so that is why the new seamax pump is a spline shaft :D Tony did it right so I am glad I am done with the Sherwood !!!!!!

[jim rosenthal]

I have Tony's breathers on both engines. Again, they are simple, they work well, and didn't cost a fortune.

OK, I'll get the SeaMax pumps. I've heard about the Sherwoods. Although to be fair, I had them on my Caterpillar 3116s and they are one of the few items on the Cats that DIDN'T give me trouble. .....go figure.

[REBrueckner]

Hey Jim, outstanding post even though I have old Detroits.

The way modern engines mix metals of inferior quality drives me absolutely nuts....in my opinion Aluminum has no place in a salt water exposed application....Worse I have looked at Yanmars of moderate size in my mechanics office, for example, and upon questioning was told the raw water injection housings (after the turbos) need to be replaced all too often because they are iron!!!! I had an ancient Onan and the combination of diesel exhaust and salt water would eat through cast iron exhaust injection elbows every other year!!!! I finally found heavy duty stainless at a plumbing supply...that lasted the next fifteen years I owned that boat...

And your zinc comments reflect prior discussions regrading 8V71TI's...the two pencil zincs in the heat exchanger/expansion tank are also out of the raw water...so they are useful maybe 100 hours annually...seems crazy!!!

A question: Your description sounds like "intercoolers" on Detroits...used to help cool down incoming combustion air....does Cummins actually call them aftercoolers?? Maybe I'm asking what's the difference between "TA" and "TI"...

[ThirdHatt]

Yup the key are junk AND A PINTA plus know to shear so that is why the new seamax pump is a spline shaft :D Tony did it right so I am glad I am done with the Sherwood !!!!!!

If you are throwing away those old Sherwood junk pumps I will gladly pay for shipping........... :)

[34Hatt]

No not throwing away actually the one was still good so that stay on board as spare. The other will go to the basement for time being but when I get tried off looking at it I will remember you Bryon ;)

[34Hatt]

A question: Your description sounds like "intercoolers" on Detroits...used to help cool down incoming combustion air....does Cummins actually call them aftercoolers?? Maybe I'm asking what's the difference between "TA" and "TI"...


Yes they do call them aftercooler such as 6 BTA it is a 6B block with turbo and aftercooled. I have also asked and wondered why aftercooled when everyone else calls it a Intercooler never did get a good answer YET!!!

Anyone know this one!

[ThirdHatt]

No not throwing away actually the one was still good so that stay on board as spare. The other will go to the basement for time being but when I get tried off looking at it I will remember you Bryon ;)

Excellent. Thank you! :)

[Fanfare]

An intercooler is located between the turbocharger and a Detroit Diesel's Roots blower. An aftercooler is after the blower, so mounted beneath it. It is a real pain to get to an aftercooler to clean it as the Roots blower has to come off and everything has to be retimed. It does give the coolest air to the cylinders as there are no more compressors to pass through and heat up the air. Detroit's aftercoolers are cooled by the engine coolant, not raw water so at least they don't leak. And they are not aluminum.

[Mike36c]

Jim, I just finished my outboard (port) aftercooler this afternoon along with a complete system Genesis acid wash and a new impeller. One tip the local Cummins experts passed along was to use Tef-Gel instead of grease on the end caps/o-rings. It's not hydroscopic and will not wash away or dry up like grease. I've been servicing mine yearly with zip issues. Most folks don't know that Cummins assembles them basically DRY at the factory, leave it alone for 3-4 years and you're buying a long block PLUS a new $1800 aftercooler. Another soft point on the B's is the fuel cooler hoses. The raw water pressure is greatest right after the pump and fuel cooler hoses have been known to blow, I change mine annually. As for the POS OEM Sherwood pump, it will last 3-5 years if the impeller is changed annually, then scrap em' for Tony's. The "B" series is one of the best marine engines Cummins produces, right along side the M11.

[34Hatt]

An intercooler is located between the turbocharger and a Detroit Diesel's Roots blower. An aftercooler is after the blower, so mounted beneath it. It is a real pain to get to an aftercooler to clean it as the Roots blower has to come off and everything has to be retimed. It does give the coolest air to the cylinders as there are no more compressors to pass through and heat up the air. Detroit's aftercoolers are cooled by the engine coolant, not raw water so at least they don't leak. And they are not aluminum.

Well that might be but a Cummins 6bta does not have a blower!

[34Hatt]

Jim, I just finished my outboard (port) aftercooler this afternoon along with a complete system Genesis acid wash and a new impeller. One tip the local Cummins experts passed along was to use Tef-Gel instead of grease on the end caps/o-rings. It's not hydroscopic and will not wash away or dry up like grease. I've been servicing mine yearly with zip issues. Most folks don't know that Cummins assembles them basically DRY at the factory, leave it alone for 3-4 years and you're buying a long block PLUS a new $1800 aftercooler. Another soft point on the B's is the fuel cooler hoses. The raw water pressure is greatest right after the pump and fuel cooler hoses have been known to blow, I change mine annually. As for the POS OEM Sherwood pump, it will last 3-5 years if the impeller is changed annually, then scrap em' for Tony's. The "B" series is one of the best marine engines Cummins produces, right along side the M11.


Tef-gel Hmmmm will have to look into that. Thanks

The POS pump actually one friend second year started leaking but it was under warranty.
Same friend is trying to get me to shit can the fuel coolers. I plan on by passing one and comparing temps in the tanks! The pressure should not be high if the system is clean!

[Mike36c]

Tef-gel Hmmmm will have to look into that. Thanks

The POS pump actually one friend second year started leaking but it was under warranty.
Same friend is trying to get me to shit can the fuel coolers. I plan on by passing one and comparing temps in the tanks! The pressure should not be high if the system is clean!


I've heard too that it's not a bad idea to ditch the fuel coolers. They say that when a cooler fails the raw water pressure is greater than the returning fuel pressure sending salt water back to the tank but I think cooler failures are rare. Anyone out there have one fail?

Also for folks still running the Sherwood crap pump (like me) watch for ANY leaks (green) around the shaft and if found remove the pump promptly. If the bearings then shaft fails the drive gear could come loose and bounce around in the case until the engine overheats or something breaks.

[34Hatt]

Also for folks still running the Sherwood crap pump (like me) watch for ANY leaks (green) around the shaft and if found remove the pump promptly. If the bearings then shaft fails the drive gear could come loose and bounce around in the case until the engine overheats or something breaks.

YUP I was like you watching last year watching and waiting but I actually had traces of salt under it before the green came. Probably would have been green with in a week or two but I switched it before that! Every time I did oil checks I wipe my hand under the old pumps.

As for fuel coolers just like you said I have heard it but never met anyone yet.
The one thing is when you get rid of them you can then get rid of the fuel block on the side and it gives more room. Makes changing Impellars easier. You know Simple is better some times :D

[jim rosenthal]

I don't think I have the fuel coolers; I'll have to look. Maybe I am better off without them; I don't run the boat that hard anyway. Usually about 2200-2300 revs, seems like the sweet spot. I think I am going to order the pumps, though, and change them out while it is still not too hot around here. If I wait much longer I'll lose twenty pounds down in the engine room. Which, come to think of it, is not such a bad idea :)

[34Hatt]

My friend gave me a S.S tube same size as the fuel cooler. My plan is to by pass one engine for a offshore trip and then check fuel tank temps and compare the difference. Will let you all know what I find out. If I only did short trips of 3 hrs or less I would have already pulled them.

[Mike36c]

The B's return a fair amount of fuel, up to 60gph@2800rpm so it will be interesting to see Dan's test results. Here's a pic of a neglected B aftercooler the local Cummins shop put on display to remind folks. There was only one bolt left securing the end cap, the bundle is actually crushed from corrosion into an egg shape, and check out rather large crack. It must have come off a Sea Ray.




http://i123.photobucket.com/albums/o303/g4commander/aftercooler.jpg

[Jackman]

Guess I'll be tackling the items you guys are rehashing...only have about 100hrs on my engines but I'm sure I'll prevent some major issues if I keep these pointers in mind.


As for the fuel coolers...I heard the same thing about f ailures but could not come up with an actual instance of failure. I spoke with Tony Athens and he said he hears it all of the time and the only example he has ever seen is when someone closed the valves for the fuel return lines while the engines were running by accident and blewem quick because of the backpressure that built up. I never understood the purpose of return lines having a valve on them....mine don't and never will. I have a valve on the supply side of the fuel system but not the return.

So I asked Tony how you test them for failure because I was having some water in fuel issues. He said you can attempt to pressure test them but you can only use something like 3-5psi because the seals will blow and then you have created work for yourself.

I will have to take notes on this thread...have a lot to learn since the repower. I still have the sherwood pumps at 100hrs of light use....will inspect them more often this season and most liely replace them next year.