In-place flush of heat exchangers on DD 8-71's

[rwaldrop13]

Has anyone done an in-place flush of the saltwater/raw water side of the cooling system and if so can you share how you did it? I am working thru the survey issues in my engine rooms, and one of the top items was flushing both heat exchangers out. With the low hours on my engines, the surveyor said a flush would be more cost-effective than removing and replacing the exchangers. I found this kit but am not sure if it would work for me. Any advice/feedback is appreciated!

MST Guardian Marine Engine Flushing System DX Series All DIESEL Engines
MST Guardian Marine Engine Flushing System DX Series All DIESEL Engines | eBay

 

[oscarvan]

I've done it, but didn't do a writeup on my blog yet. I bought an extra water pump cover plate and mounted a hose on it. Removed the impeller and put the plate on. I have a small bilge pump that sits in a 5G bucket and pumps the flush into the water pump housing. (Barnacle buster for instance). I disconnected the hoses that send the water into the exhausts, made a PVC piece to connect them and then feed back into the bucket. I remove the zincs and have plugs to put in their place. I also have a scope that I send into the various locations to check for debris.

 

[Dan Mapes]

I did it a couple of times on 6-71s and while there are some subtle differences, I'd make sure to include the transmission cooler in the loop if installed and it is prior to the raw water pump in the loop. Yes, pull all the zincs and plug them up with old empty zinc brass.

 

[rwaldrop13]

I've done it, but didn't do a writeup on my blog yet. I bought an extra water pump cover plate and mounted a hose on it. Removed the impeller and put the plate on. I have a small bilge pump that sits in a 5G bucket and pumps the flush into the water pump housing. (Barnacle buster for instance). I disconnected the hoses that send the water into the exhausts, made a PVC piece to connect them and then feed back into the bucket. I remove the zincs and have plugs to put in their place. I also have a scope that I send into the various locations to check for debris.

Thanks! What you are describing is essentially what I was thinking after seeing a cruising couple on YouTube do something very similar. The only difference is they bought the fancy kit from EBay. I appreciate the info, I am going to work on setting up my flushing system.

 

[rwaldrop13]

I did it a couple of times on 6-71s and while there are some subtle differences, I'd make sure to include the transmission cooler in the loop if installed and it is prior to the raw water pump in the loop. Yes, pull all the zincs and plug them up with old empty zinc brass.

Thanks for the feedback! I was pretty sure it could be done, Oscarvan described what I thought would have to be done and you reinforced it. Going to assemble my own homemade flush kit.

 

[SKYCHENEY]

I pulled the hose off of the shower head and fed the solution in there. I pulled the hose after the raw water pump at the elbow to feed it back to the bucket. That way I never had to mess with the impeller.

 

[MadHatter53]

Might as well do your AC also.

 

[SKYCHENEY]

Might as well do your AC also.

And generator

 

[oscarvan]

I pulled the hose off of the shower head and fed the solution in there. I pulled the hose after the raw water pump at the elbow to feed it back to the bucket. That way I never had to mess with the impeller.

I replaced the impeller while I was in there.

 

[sgharford]

I did in flush on my Cummins 903's at beginning of season. I used Klean-Strip® Concrete & Metal Prep - It's a 35% to 45% Phosphoric Acid Concentration. Look out for other concrete etch products like "Rustoleum Clean and Etch" - it's actually Urea, not phosphoric Acid. I used it few years ago by mistake, it does not work nearly as well as actual Phosphoric acid solution.

I know you are doing a DD, but thought this relevant as well. I would keep the circulation bucket at least 2' above the highest point on engine. I initially had bucket about 1' above, but after running solution for several hours and using a borescope to check out, the solution did not make it to about top inch of return side of my heat exchanger. Guessing was not enough head pressure with pump (think a 500 gph Rule bilge pump) to really force it in there with backpressure resistance of fluid. I raised bucket another foot, and ran another hour which took care of that top inch.

Another suggestion with your new flush kit, test it with fresh water only first for leaks before running with actual acid solution. Fixing a leak may involve allowing your solution to run into the bilge - a PIA and waste of acid. When done, I hooked raw water outlet back to exhaust elbow and ran allot of fresh water through it. This way when you replace the impeller you only have fresh water coming out.

Below a picture of that top inch I was talking about.

 

[racclarkson@gmail.com]

I know you are doing a DD, but thought this relevant as well. I would keep the circulation bucket at least 2' above the highest point on engine. I initially had bucket about 1' above, but after running solution for several hours and using a borescope to check out, the solution did not make it to about top inch of return side of my heat exchanger. Guessing was not enough head pressure with pump (think a 500 gph Rule bilge pump) to really force it in there with backpressure resistance of fluid. I raised bucket another foot, and ran another hour which took care of that top inch.

Always loop the discharge hose well above the motor. This will build enough back pressure to completely fill the system. In addition, I'll pinch off the return line some with a clamp to ensure 100% coverage. I do this after the solution starts to run clean.

 

[rwaldrop13]

Thanks everyone! My plan is to pull the hose at the raw water pump and connect my bucket there (setting it about 6 inches above the engine on wooden blocks) and running it for several hours at a time. Based on what surveyor said, plan is to run solution for a few hours then switch to fresh water for overnight then diluted solution second day. It may be overkill but it's first time for this process and I want to be thorough.

Generator has already been done - The impeller had shredded and I had to back-wash the HE on the genny, then I flushed it and HE core is actually newer than the genny.

One other topic - regarding AC's, I actually have a flushing system I built using a spare faceplate/inlet on the pump that I connect to my washdown hose. Once I have it in place, I go out to the dock/pedestal and slowly open the valve for the washdown hose while watching the discharge opening. Once I have a steady stream of water there, I leak-check the units/hose runs (I have standalone units in each stateroom, V-berth shares with galley). Once I remove the last 2 defunct Crusair units from the generator room, plan is to put inline valves in the hoses before the overboards so I can recirculate barnacle buster or something similar thru the units like I will with my engine.

 

[racclarkson@gmail.com]

I think you’re making a mistake. You really don’t want to keep the acid in there anyway near that long. Get the mix right and once is enough. I’d also not use the same solution on the ac’s. You can do a lot of damage if you overdose or over do it.

 

[MadHatter53]

How about some pics of your set up when you get a chance.

 

[rwaldrop13]

I think you’re making a mistake. You really don’t want to keep the acid in there anyway near that long. Get the mix right and once is enough. I’d also not use the same solution on the ac’s. You can do a lot of damage if you overdose or over do it.

So flush it with solution for a while then flush with freshwater for at least same amount of time?

And I don't use solution on AC units, I use washdown hose with dock pressure - Works great to blast guck thru system.
.

 

[rwaldrop13]

How about some pics of your set up when you get a chance.

Will do - Won't be anything fancy, Lowes bucket and hoses with PVC adapters in hose ends. Goal is to flush HE's on both engines without breaking the bank. Lot of great advice on here, much appreciated.

 

[racclarkson@gmail.com]

So flush it with solution for a while then flush with freshwater for at least same amount of time?

And I don't use solution on AC units, I use washdown hose with dock pressure - Works great to blast guck thru system.
.

Well, I'd strongly urge you to get a Depstech unit so you can evaluate the before and after.

With the proper strength solution, you're looking at 90-120 mins. The solution should start coming out clean well before. You should reverse the flow the last 20-30 minutes before rinsing.

Rinsing 15-20 mins is fine. The best rinse is to just start the motor.

Here's a good Depstech after view.


I recommend a white vinegar solution overnight for the AC.

 

[rwaldrop13]

Well, I'd strongly urge you to get a Depstech unit so you can evaluate the before and after.

With the proper strength solution, you're looking at 90-120 mins. The solution should start coming out clean well before. You should reverse the flow the last 20-30 minutes before rinsing.

Rinsing 15-20 mins is fine. The best rinse is to just start the motor.

Here's a good Depstech after view.
View attachment 52415

I recommend a white vinegar solution overnight for the AC.

Robert, I love using white vinegar - I flush it down my saltwater toilet, I spray down shower stalls with it, and I pour some into shower sumps weekly... Once I remove the last 2 defunct Crusair compressors, and can put a vlave/loop fitting at the thru-hull discharge fitting I will be able to circulate white vinegar thru the AC system, but in the meantime I settle for flushing the units from the pump to the overboard with dock water. I made a flush tool with a pump faceplate and a piece of 3/4" hose, with a union to connect to my washdown hose.