Acid flushing your cooling system

[djmarchand]

The Cummins-Yanmar thread suddenly morphed into acid flushing, so I thought I would start a new thread specific to acid flushing and repost something I posted to boatdiesel last year:

This discussion is specific to the Yanmar 6LY but the general principles are applicable to any marine diesel.

Today I tackled acid flushing the raw water cooling side of my engine. I had disassembled, cleaned, greased and reassembled the air cooler about a year ago, but now it seemed time to do the entire system.

In the summer at a cruising rpm of 2,800, the engine temp runs about 190 and rapidly increases to 200 or so at wot. No real problem; the engine doesn´t overheat but the rapid temp increase at wot led me to believe that the raw water heat exchanger was marginal. And AFAIK, it had never been cleaned in ten years and 800 hours.

My first approach was to remove the main heat exchanger. But after partial disassembling it and looking at the half dozen or so hoses that needed to be detached to get it out, I decided to leave it in place and acid flush the whole system.

So I first pulled out the raw water pump. I used its rubber elbow as the supply attachment to the circulating loop I hooked up. I used a couple of PVC/nylon fittings and a hose to a spare bilge pump I had laying around. The return hose was simply the raw water hose that normally goes to the exhaust elbow.

I used one gallon of Barnacle Buster mixed with a gallon of fresh water. You can use Rydlime, CLR, etc. But I don't believe in HCl- swimming pool acid. Too corrosive.

The first picture shows the bucket and hoses to and from. The Barnacle Buster solution immediately turned black so I knew it was doing something, but you can´t see the bilge pump as a result. The second picture shows the attachment to the rubber elbow. The corrugated white thing in the back is a plate I made from an old pvc shingle to block where the raw water pump normally bolts to the block- keep oil in and trash out.

Before adding acid you have to remove all zincs. Zincs will quickly waste in acid and will deplete it unnecessarily. So remove the brass cap, unscrew the zinc and reinstall the brass cap.

Also pinch the prop shaft log cooling hose with a pair of vice grips or similar. This is shown in the third picture.

I did something a bit unusual. I used engine heat to heat up the system a bit. It was 40 degrees in the engine compartment when I started this morning. So I hooked up a water hose with duct tape to the water injection elbow to keep the exhaust hose from overheating. You can see this in the first picture. I then started the engine and let it warm up at idle in reverse gear. When the dash gauge showed 160, the circulating solution felt like 100 degrees so I stopped the engine at that point. I restarted the engine every hour for 2-3 hours. I only ran the circulating pump for 5 minutes every half hour or so.

The fourth picture shows the Barnacle Buster solution after 15 minutes. Something was getting dissolved by the BB!!!

After acid flushing, I dumped the acid and dropped a garden hose into the bucket and displaced the acid with fresh water. I then hooked up the exhaust elbow and flushed some more with the engine running.

I will post temperature results the next time I go out, but with water temps now down to 50 or below, I won´t really know how it worked until the middle of next summer.

David

 

[Bill_N]

What affect did you see on engine temps after doing this?

 

[Brooksie]

Mild acid may be OK, if that is what Barnical Buster is, but Yanmar's have a lot of aluminum and should not be flushed with alkaline containing products. I'd be more apt to get something at the autoparts store specifically for "mixed metal" engines that comes with nutralizing instructions.

 

[djmarchand]

Bill:

Like I said in the post, I won't really know about engine temps until mid summer when the water temps are in the 80s. They are 40 now which is too cold to show any cooling system problems!!

Brooksie:

Aluminum is not in contact with the seawater side that the posting talks about cleaning. Aluminum is on the coolant side or the air side of the heat exchanger. The seawater side is bronze castings separated from the aluminum shell with O-rings and cupronickel tubes in the heat exchanger bundle.

Any cleaning solution that won't affect aluminum isn't going to remove scale either. And aluminum is an in between metal- it is affected by both acids and strong bases.

If you run the engine either at the dock for a few minutes or preferably take her out for a spin, the raw water pump will flush any residual acid out quickly.

David

 

[Bill_N]

Saw the "last year" statement and figured you'd run it.

 

[[email protected]]

Mild acid may be OK, if that is what Barnical Buster is, but Yanmar's have a lot of aluminum and should not be flushed with alkaline containing products. I'd be more apt to get something at the autoparts store specifically for "mixed metal" engines that comes with nutralizing instructions.

Be careful. I think Brooksie's correct. If I'm not mistaken the aftercooler, the lube oil cooler, and the heat exchanger on those engines are all aluminum housings and raw water cooled. If any part of that o-ring area isn't perfect the acid will attack the housing. When I service an aftercooler and it is so contaminated that it needs corrosive cleaning, I send just the element, not the aluminum housing to a radiator shop. They use whatever they use and then neutralize it, and then I install the element into the housing with new seals and pressure test it. I'm not a Yanmar tech, but from what I've seen all their engine coolers are aluminum housed and raw water cooled. When I worked for Cummins we did not acid flush the sea water system.

 

[djmarchand]

Mike, you are mostly correct. If you noticed in my posting I said that I had just serviced the air cooler. I would never acid clean an engine with an aluminum air cooler if I hadn't first serviced it to make sure that there was no corrosion around the O-rings and that they were sealing tight.

The Yanmar 6LY is particularly amenable to this. The air cooler is fairly accessible but some of the others, particularly the lube oil cooler which sits under the air cooler is a bear to physically remove.

Excepting the time to service the air cooler, the whole acid flushing job took about 4 hours. It would have taken 2-3 times as long to physically remove each cooler, disassemble and separately acid clean their tube bundles. The main heat exchanger is sealed with gaskets, not O-rings and is not likely to corrode at the margin. Same for the transmission and lube oil coolers. So the risk of acid getting past the gasket to the aluminum is limited.

I think that acid flushing the entire system is a reasonable compromise as long as you have previously serviced the air cooler.

Thanks for pointing the potential for corrosion and leakage around the air cooler O-rings. It was buried in my initial posting and should have been made more obvious.

And for a severely fouled raw water system with plugged tubes, you have no choice but to disassemble everything. Acid won't do a thing for a plugged tube. It has to be rodded clear first.

David

 

[petrel]

Of course if you take your coolers to a radiator shop you can also have them pressure tested, which would be a good idea if they have some age and or you don't know how well the zincs have been kept up previously.

 

[Pitou]

Good right up.

I've almost always used the Rydlyme making a similar loop with nylon fittings to washing machine hoses. One hose connected to the sump pump in the 5 gallon bucket and one loose in the bottom for the return. With zincs removed and shaft seal water supply line plugged, I first run the loop in reverse from the heat exchanger and exhaust it out of the intake hose of the aftercooler bypassing the water pump. After 30 minutes I reverse the flow for another 30. First time I did this I dropped the temp from 198 to 180.

This process is great for off years, but there is still the need to take things apart, visually inspect, replace gaskets, lubricate and maintain the air side of the cooler. For me this piece is every 3 years.

Here's a picture of my last flush on my 6BTA on the old boat in 2012.

 

[captainlarry84]

Only way to go, The days of disassembly are over. I highly recommend using a wash system. I like Rydlyme. A little time consuming but no disassembly. Just make sure to remove all zincs & pinch off the dripless feed. Works like magic!

 

[tunaorlater]

We did this to a pair of 60 series volvo's last year that had been sitting a few years and were overheating. It was worth a shot before tearing down the entire system, needless to say I wasn't a believer. Once we ran 2.5 gallons through each engine over night the temps were perfect, I couldn't believe how easy it was. I think a 5 gallon bucket of Rydlyme from Jackson's marine was $150.

 

[[email protected]]

I don't think the days of disassembly will really ever be over. Put another way, lets say you were looking to buy a 10 or 12 year old vessel with a high performance diesel (3/4 HP per cubic inch or more) and had hired a mechanic specifically to look at the engine package and to let the hull surveyor concentrate on the boat. During sea trial the engine constantly ran too hot at high RPM's and with low temperature drops across the coolers. Which report would make you feel your interests were best served? 1) Vessel sale contingent on present owner having cooling system components disassembled, cleaned, inspected, resealed, and tested - or 2) she'll probably be OK if we run some stuff through her. / both subject to sea trial. Flushing might alleviate some flow and heat transfer issues but these coolers are fragile, call for thorough inspections at minimum 5 year intervals when used in salt water, and when failing can cause catastrophic engine damage.

 

[jojobee]

Ultrasonic when disassembling them
Rydlime for basic maintanence

 

[FPTMarineDiesel]

I don't think the days of disassembly will really ever be over. Put another way, lets say you were looking to buy a 10 or 12 year old vessel with a high performance diesel (3/4 HP per cubic inch or more) and had hired a mechanic specifically to look at the engine package and to let the hull surveyor concentrate on the boat. During sea trial the engine constantly ran too hot at high RPM's and with low temperature drops across the coolers. Which report would make you feel your interests were best served? 1) Vessel sale contingent on present owner having cooling system components disassembled, cleaned, inspected, resealed, and tested - or 2) she'll probably be OK if we run some stuff through her. / both subject to sea trial. Flushing might alleviate some flow and heat transfer issues but these coolers are fragile, call for thorough inspections at minimum 5 year intervals when used in salt water, and when failing can cause catastrophic engine damage.

I agree, you can't just clean the sea water side only anymore, there is plating that takes place on the air side of a cooler especially when there is a CCV system installed which most engines have now, (emulsification), residue, etc. On the HXC side the coolant will plate the core and create an insulator so that heat does not trasfer to the sea water as well. You still need to clean the external cores, inspect the o-rings for hardening and the end caps from time to time.

 

[Madchark]

DJM,

Looking to see how many hours you had on the yanmar when you did the flush.

 

[djmarchand]

Madchark:

Ten years and 800 hours. I don't think it had ever been cleaned before. Like I said I won't really know how effective it was until the middle of this summer when the river temps get to about 80. But the acid solution sure turned black!!!

David

 

[Pamlico]

After reading this thread I decided to flush the raw water coolant side. Last summer anytime I ran over 1900 she would heat up to 200 degrees. I picked up 2 gallons of Barnical Buster and hooked up a homemade circulation system and flushed for about 6 hours.

Launched the boat on Sunday morning and ran around the river for a few hours. The Barnical Buster did wonders. No signs of heating up, not even at WOT (2600 RPM's) she never moved over 190 degrees. I'm sold!