Acid Flushing Your Engine

As discussed in another thread, I have decided that routine fresh water flushing does minimal good and has a problem with using the proper zincs for fresh and salt water protection. So I wrote the following article instead, but specifically for acid flushing to remove scale and marine growth, not fresh water flushing.

I had hoped to have it published in boatdiesel, but Peter Compton's requirement that no references be made to Tony Athen's site Sbmar.com led me to stop following and participating in boatdiesel.

So, here it is for your reading pleasure. I will also upload it to the Library hee after I edit it for any comments that I receive.

David

Dave- Two comments:

1. Do you think it is beneficial to end the process with a basic solution to neutralize acid hiding in crevices? This is more in your realm than mine, you being a ChemEng and me MechEng. I don't know the answer.

2. One thing I rec to my guys is try to schedule acid cleaning before some sort of long trip so it naturally gets lots of post treatment flushing.

Just a case in point: A guy flushed his engines then it sat on the dock for a month or two. He had a starting issue and called me out. I got that sorted and fired up the engine. Walked back to the transom to check for water flow as I usually do. Out the tailpipe came a large plume of reddish something. Best I could figure it was some sort of Cu oxide that was being created in the acidic environment remaining in the coolers. Nothing was leaking, but it could not be good for cooler life.

"1. Do you think it is beneficial to end the process with a basic solution to neutralize acid hiding in crevices?"


An excellent point ..... when I must acid flush which is rare - I follow up with a mixture of soda ash available cheaply at any pool supply store. Circulating the soda ash for at least 5 minutes before a water flush will neutralize the acid 'hidden' in the small places.Those hidden places ate typically where the soldered and brazed joints live affectively the weakest locations.

Well, guys soda ash neutralization can't hurt. When I did this on big industrial heat exchangers a hundred years ago we finished with a 100 lbs of soda ash and then checked the pH of the return solution after circulating the soda ash for 30 minutes or so to make sure it was alkaline. But we often had dead piping legs that needed some help to get them neutralized.

The reason I didn't explicitly recommend it, is that the raw water flow in a marine engine turns over the volume in the heat exchangers in less than a minute at idle, whereas in our industrial world it was more like several minutes. The turbulence at that high flow rate should get even the pockets flushed out and they aren't deep in any case.

To Ski's point, the best way is to run the engine up to a couple of thousand rpm to really push the water through it while underway. Fifteen minutes of that and I guarantee there will be no acid left anywhere.

And, yes letting the acid sit there for months will certainly corrode the cap and tubes and result in a reddish solution when finally flushed out. I can't quote specifics but if acid will eat through 1/8" thick carbon steel in 24 hours (it will), then it would certainly eat through ten thousandths or so of cupro-nickel in a few months.

Also, I should note that what we used on industrial equipment was HCl with a corrosion inhibiter that reduced corrosion 100 fold so it could be used on carbon steel. There is no corrosion inhibiter in Barnacle Buster which is nuts when you are paying $50 per gallon for the stuff.

FWIW, industrial plants that use direct sea water cooling used to use cupro-nickel tubes in my day and they would last 20 years or so. That of course is 24/7/365 service and probably a lot hotter temps on the other side than we see in our engines. They now use titanium tubes, but that would be way overkill for our engines.

David

djmarchand said:

As discussed in another thread, I have decided that routine fresh water flushing does minimal good

David

Click to expand...

Thanks for letting us know about your decision.

Just curious if that's a decision based on some sort of sample that was compared between the different techniques over long periods of time?

great article, thankyou.You do not recommend a yearly treatment, but would you only do on temperature rise, or would a much gentler schedule be advised (say every three seasons) as a preventative measure, instead of waiting? thankyou

Kev:

That opinion was based on observing how after coolers fail. Protecting my after cooler was the prime reason for starting fresh water flushing several years ago. I looked at a dozen or so pictures and descriptions of failed after coolers on boatdiesel and they all failed first from corrosion on the air side, which fresh water flushing won't do anything for.

I only have personal experience with one after cooler, the one on my Yanmar 6LY and it is in pretty good shape. I believe that Ski agrees with my conclusion and he has seen many more first hand.

Fresh water flushing also brings into question which pencil anodes to use to protect the raw water side components. If you do a fresh water flush then you should probably use aluminum anodes which are effective in salt and fresh water. (Source- ABYC and aluminum anode manufacturers).

But I believe that the metals in raw water systems- mostly bronze and cupro-nickel are very corrosion resistant in salt water, particularly if protected with zinc anodes, so that fresh water flushing does minimal extra good.

David

tinped:

I think a lot depends on your engine and how it reacts to raw water system fouling. Mine seems to just get a little worse, ie higher wot temps, each season so there is plenty of time to catch it and do an acid flush. As best i can tell mine has been acid flushed only once about 3 years ago at the 10 year age and it dropped the temps about 5 degrees.

So in my case, I am just going to watch the temps. It certainly helps that I boat in LI Sound where water temps are relatively low. If I were in the Gulf Coast, I might acid flush on a 3-5 year schedule.

David

One question, is there any heat echanger out there made of more "high tech" material like carbon fiber?
I am surprise to see that in a highly corrosive environment like sea salt material used seems always the most prone to corrosion on the engine side.
Sure a heat exchanger made of carbon fiber would cost more than cast iron but compared to the overall cost of a boat... peanuts.
But I may also be totally out of my mind here

Lou:

First of all, after coolers are made with aluminum housings because they have to be BIG to pass all of that air. My after cooler's diameter is double the main heat exchanger's. So aluminum is used to keep the weight down. Other heat exchangers are made with cast iron housings which last much longer.

Yes, I think that carbon fiber could be used to build after cooler housings. It would have to have precise, machined quality flanges for the core and caps to seal up to it. But I have seen carbon fiber masts and booms with that kind of quality. The Cummins QSB 6.7 uses composite caps but has an aluminum housing. Maybe there is hope for the marine engine industry if they will just take the next step and make the housing out of composites also.

I think that another reason is that most engine manufacturers only understand metal casting and fabrication and don't know beans about composite construction. They also don't see it as a big problem. Even if you don't do a thing about service, a Yanmar after cooler will last at least ten years (mine did) and maybe 20. Cummins after coolers will last half of that time because the core is mounted vertically and air side condensate just sits on the lower air/water o-ring joint.

So maybe there is an opportunity for some smart carbon fiber composite firm to make after market after cooler housings.

David

Just a comment on the Cummins coolers. The end caps are quite concave. They would probably hold 6 oz of water. The bottom cap has a condensate drain, so water does not sit in there in the O ring joint. The bottom end cap will drain completely when the engine is shut down.

I recently thought of buying a boat with a single, large CAT engine in it. As it had been serviced by a CAT agent I rang them (with the owners permission) to ask what needed doing.

Almost the first question was had it had a new heat exchanger (it was 10 years old). It hadn't so the CAT man explained on this engine the heat exchanger needed pressure testing and cleaning every two years and replacing every 6 years (the cost a mere £4200 for the part {about $US5K)). They recommend changing not because of wear but because of corrosion.

Yes I know you may say its unnecessary but I couldn't take the admiral across the English Channel or down the Alderney straight without an engine I feel 100% sure about, especially as it was the only one in this boat.

The engine is designed to do 3 - 5K hours a year. If you do this then £1000 a year for this one part doesn't matter, but to me with my 200 hours a year it is a tad expensive.

Not all Cummins engines have or had condensate drains and that has led to a lot of damage with these assemblies.


I have seen many (all actually) cast bronze aftercoolers last 25+ years up to 30 years with little or no service and no failures on Hino engines.

On the heat exchangers which I am aware of - maybe 60 or more- they have rarely been acid cleaned and run in salt water for at least 15 years with no issues and with some up to 25 years. In most cases these boats run at higher engine loads (60-75%) and temps as they are mostly used at 15-18 knots in larger heavier boats.


With some limited experience with carbon fiber assemblies in association with non ferrous metals the TCE was too excessive to allow for a reliable seal. Most of these testing applications were in military assemblies and had continuous failures at junction points and required heavy maintenance which was determined to be above its worth at the time. Perhaps the past 12+ years with these mixed assemblies has yielded better results but I am no longer aware of those updates and/or improvements.

"FWIW, industrial plants that use direct sea water cooling used to use cupro-nickel tubes in my day and they would last 20 years or so"


Hello Dave,

That is very interesting. It has been quite some time but I was inside a bunch of 'very large' tanks and intercooler systems in a past life. We used to clean out these large heat exchangers and commercial systems for power generation as well as inside of multi-million gallon fuel and oil tanks.
I cannot say I miss the work or the stress of being inside a fuel tank.

"There was a service bulletin issued in 2008 (I think, might have been 2007) to retrofit a drain in the cooler end cap. It was just a small hole drilled in the bottom of the aftercooler."


This is the way I remmeber it .....
- there were numerous failures and problems with wnterizing
- many engine failures as a resulst of these problems
- Cummins originally said there was no issue and it was due to operator and servcie error
- a number of owners beacme irate and began a campaign to rectify this
- that eventually turned into a class actions lawsuit
- Cummins evetually setlled by repairing/replacing any engines and assemblies claimed at the time
- There remains many owners who did not know about the issue and may have problems now or in the future


Waht I do remember does not share too much with your post above - "The bottom cap has a condensate drain, so water does not sit in there in the O ring joint."


Here is a link to what is left of the lawsuit site....
https://topclassactions.com/lawsuit...iesel-engine-class-action-lawsuit-settlement/

If I was Marin I would post a couple of pages on this issue. Me...all I have to say is this:

1. No engine mfg recommends acid flush. Most say it is harmful to components.
2. Acid will not flow through a completely blocked tube.
3. Acid flush will not clean the air side of an aftercooler.
4. Acid flush can partially dissolve a salt block in the afercooler that will let go once you get the engine up to cruising speed later. You might not know this happened until too late.

Gilbertpark, one of my favourite pubs is in Emsworth! Can't remember the name but it was my favourite cousin's local, full of smokers and wet Labradors and very nice people. The name might come to me some time in the night...

The Sussex! Yay!

djmarchand said:

So, here it is for your reading pleasure. I will also upload it to the Library hee after I edit it for any comments that I receive.

Click to expand...

Good article.

Think maybe useful to suggest heat exchange acid flushing in situ can be very useful, especially to treat immediate symptoms easily... but that it's not a perfect replacement for periodic off-engine service.

Ditto similar comment ref aftercoolers, plus a note that acid flushing doesn't reach the air side... so following manufacturer's service guidelines is still especially important for aftercoolers.

FWIW, I flushed our system with Rydlyme a couple years ago. One engine using the recirculate technique, one engine using the fill/sit/flush approach. This would have been on 12 year old engines, with periodic scheduled aftercooler service but with nothing much (that I was aware of) done to the heat exchangers during that period. A couple few raw water hoses in the circuit had been replaced along the way.

A) No difference in temps before or after, either engine. B) No difference in the Rydlyme outflow at the end of all that; both equally a bit cruddy. C) No easily perceived difference in normal raw water flow afterwards. I deduce it wasn't particularly necessary. OTOH, I still haven't yet dismounted the heat exchangers for off-engine service, so I'm not able to say they'e better (or not) afterwards.

OTOOH, I flushed our genset at the same time, and the stuff did a very good job on that heat exchanger... which really needed it at the time! I did have that open at one end, and could really tell the before/after difference!

-Chris

The lead in title could better read " How to Chemically Clean Marine Heat Exchangers." Or better yet, "Fresh Water Marina Locations."

For me, no chemicals on our vessel's systems. Either manually or with ultra sonic cleaning. That said, each location and application is different so an open informed mind is OK.

Ours too - best Sausage Pub ever been too. Never mind blocking up coolers who knows what a surfeit of sausages will do to your coronary arteries!

David,

I've been thinking about this posting for awhile and really need to respond as I feel very strongly you are putting out some very bad info, or at very least, giving mis-guided info based on a very limited amount of field data.

My goal here is to help all, not to disagree, but to show that what you are saying, has no basis in long term application--It's really no different than the couch engineers at Cummins that never heard the term "Marine Age" nor understood what really is going on inside any aftercooler of mixed metal construction in the field... What is "says" on paper , including "zincs" has ZERO value is real life or in actual application........ Here goes:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



Give me an honest & accurate answer on this one..

Tell me, as best you can, how many Cummins aftercoolers on mid-range engines you have put into service when new, (like you had from when the engine was brand new), and then maintained that engine over the next few decades, and then serviced the same aftercooler over and over throughout the years, by pressure testing it over 10 to 20 years on a regular basis, and then put together all those experiences together based on what you observed and tested over the 10-20 years that these base designed aftercoolers have been around? How many would you say?

What I am really having an issue with is your current thoughts on fresh water flushing and zincs.

On this subject—How many aftercoolers and engines have you worked on that spent 10-20 years in Lake Michigan or any fresh water lake and then had the 1st opportunity to take apart and service the entire engine-seawater side since launch date of the engine – 15+ years and/or about 500 total hours since new, or something similar?
Fill me in here as maybe I am missing something in the 30+ years I’ve been dealing with Cummins aftercoolers on the mid-range engines. Maybe close to 1,000 coolers later with notes and pictures of 100’s of them..

Help me help the readers on these forums to get this all into a true perspective based on real experiences over decades and not “one or two off” observations…

Tony

Tony

Good comments. Glad to see you are keeping a weather eye on us.

Tony:

I acknowledge that you have more experience than all of us. But...

I just saw some pics on your forum of a corroded after cooler. The bronze face had light pitting that cleaned up easily by block sanding. The aluminum face had severe corrosion and you recommended taking off as much as 1/8 of an inch to try to fix it.

That corrosion almost certainly started on the aluminum air side and maybe when it breached the seal, the salt water got through and accelerated the corrosion to the aluminum. Fresh water flushing won't stop this from happening if it starts on the air side.

The only possible benefit that I can see from fresh water flushing is that when the seal is breached then after shutdown you won't get sea water pushing back into the aluminum side. But with no pressure on the system I doubt if that happens in any case. But there will be residual sea water on the air side that got there while running the engine after the seal is breached and that is probably what really corrodes the aluminum leading to a gross failure followed by engine failure.

Sure boats operated in fresh water lakes don't have after cooler failures like sea water operated boats. They operate in an an environment free of salt air. Aluminum is pretty corrosion resistant in fresh air condensate.

And finally I think that the best solution to any operating and design problem comes from looking at the facts (experience) and analyzing them from a theoretical basis (couch engineering) to try to figure out what causes them.

Maybe working together we can do this- using your experience and my theoretical perspective and come to some agreement. BTW I posted the question about fresh water flushing to your sbmar.com forum a week or so ago and you did not respond. We can continue the conversation there if you like.

David

David, you will find that the primary source of salt on the air side, is salt laden combustion air drawn into the aftercooler. The condensation on the tubes is salt water. the condensation drops to the bottom of the aftercooler. Eventually the water evaporates leaving behind salt crystals. That is how you get salt and corrosion on the air side of the cooler. this is the reason why it is important to service the aftercooler every year, or as often as recommended by the manufacturer.

You do not need to have the O ring seal breached to get salt water on the air side. I have seen a number of aftercoolers with the tube bundle corroded into place, but no salt water in the combustion air. I have seen an after cooler seal fail and destroy an engine. In that case it appeared to have been caused by a severe engine overheat.

I too would appreciate Tony's perspective on this. He is the one that services a lot of these aftercoolers. Tony, where is the corrosion in the aftercoolers that you have seen causing issues? Is it on the air or water side?

I would be interested in setting up a fresh water flush on my engine IF it can reduce the time between services on my aftercooler. If not, then I don't want to bother.

Tony,
I think we all agree that you have cracked in to more diesels than anyone on this forum, but what are your thoughts regarding the authors original premise? IE, do you think acid flushing has any value? Everything I have read is anecdotal, but it does appear some people have found it useful, others, not so much.

Fletcher:

I think Tony was questioning my view that fresh water flushing does little good, not whether one should acid flush.

David