QSC aftercooler maintenance

b_arrington

Well-Known Member
GOLD Sponsor
Feb 21, 2007
3,469
Setauket, NY
Boat Info
Back Cove 37
AB Ventus 9VL
Engines
Cummins QSC 8.3 600
This week I completed a full aftercooler service on my Cummins QSC 8.3. I thought I’d share what I found. It had 3 years and 235 hours on it, and this was the first service. It looked better than I had hoped/was afraid of. This was in large part because last season my generator’s heat exchanger was completely blocked with scale. I think the regular fresh water flushing was a big factor - I have a flush port on the strskner cap and flush every time the engine is run.

For servicing I removed the core, cleaned it inside and out and reassembled using the Seaboard Marine aftercooler service kit and their protocol with lots of grease.

Observations
  • The instructions in the Cummins owners maintenance manual are very rudimentary.
  • The bolt highlighted by the red arrow i. The pic below is tricky. You have to remove all the other bolts (including 8 under the AC), then slide it over to get access.
  • 90% of the weight is the cooler core. The housing is very light!
  • The rubber strips on the air side of the core are stupid. All they do is make it hard to remove the core.

What I did for service
  • Soaked the raw water side in an acidic solution to remove scale. I left on the caps, poured in the solution, and let soak.
  • After, flushed with fresh water and rodded out each tube with a gun cleaning rod/brush. Removed a lot a junk.
  • Remove the core. A bit tricky and required patience plus some careful application of force. Also lots of Kroil penetrating oil.
  • Soaked the remove core in a bucket of detergent to clean the air side then rinsed.
  • Removed the dumb rubber strips for the air side of the core.
  • Cleaned the caps of all old grease.
  • Carefully sanded/polished minor corrosion from all mating surfaces with ultra fine sanding cloth, plus a lubricating oil. Also lightly sanded the inside of the housing to remove light corrosion.
  • Liberally applied Alco Metalube grease to all mating surfaces plus the first 2”-3”’of the housing. This will make any future disassembly much easier and help prevent corrosion.
  • Reassembled - it went back together very smoothly with the grease and light sanding.
The one thing I didn’t do was a pressure test on the core/housing. But based on the good visual condition and low hours I’m ok with that.

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Nicely done. I personally never acid clean the water side. I’m in salt 24/7 and don’t freshwater flush but use my boat enough that I don’t get much, if any, scale blocking the tubes. If I do the scale is only at the very end and only goes about 1/8” into the tube. Poking that free/roding out is all you need to do. I do remove the caps and clean them with muriatic acid if they need it.
 
Brad, as always, thanks for a great write up. I appreciate the time and effort you put in to giving everyone a solid example of how this big maintainence task is done.
 
To be honest I know I'm capable of doing this "straight up" mechanical task but really don't want to take a chance of F****ing up my QSC's with a rookie mistake. On the other hand if you were side by side with me.... I'm sure it's a "see one, do one kind of job." Feel like coming out to Jersey? :D
 
Great write up. One thing I did on the second go around of servicing my AC was to do a 2 hour flush with barnacle buster before removing them for cleaning. This cleaned out the tubes very well and removed the need to rod them out.
 
To be honest I know I'm capable of doing this "straight up" mechanical task but really don't want to take a chance of F****ing up my QSC's with a rookie mistake. On the other hand if you were side by side with me.... I'm sure it's a "see one, do one kind of job." Feel like coming out to Jersey? :D

Brewster - when you get done come on down to Eastern Shore MD. :)
 
Great write up. One thing I did on the second go around of servicing my AC was to do a 2 hour flush with barnacle buster before removing them for cleaning. This cleaned out the tubes very well and removed the need to rod them out.
Good idea. I haven’t built a flushing rig yet. I might do that for my heat exchanger.
 
...One thing I did on the second go around of servicing my AC was to do a 2 hour flush with barnacle buster before removing them for cleaning. This cleaned out the tubes very well and removed the need to rod them out.

That's exactly what I always did and it worked very well.
 

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