How do I clean a sticky dirty heat exchanger on the coolant fresh water side?

[sdowney717]

This is a Sen-Dure unit. I can using my fingernail scrape off a layer of slightly sticky stuff from the tubes. This is the coolant side of the unit, not the raw water side.

Looking down the coolant side exit there is this buildup on the tubes, which I scraped off with a fingernail.

Whole thing. I removed it to silver solder the drain plug pencil zinc holder. I then JB welded the ends, and will repaint it. I notice when feeling inside at the cap, it also has a coating of the same stuff, so I think it is all over the inside of it. I may use spray on oven cleaner (lye) to clean it. I know this is made with copper-nickel tubing. All the rest is copper and brass. Mostly copper.

 

[montero]

What kind of coolant it was ? Raw water flows through the tubes?

 

[seasquirt]

Hi sdowney. It could be a leak stop treatment, or a precipitate from mixing incompatible coolants. Try hot water and detergent and gentle compressed air to create bubbles - don't over pressurize it. That should remove some. Next is a water soluble degreaser using same method. If still coated try kerosine or white spirits with a long squirt of carby clean spray. After that then try lye, but don't leave it in for long, and flush it out thoroughly to avoid corrosion. There are many other cleaning methods to try. I'm sure several will be shown here soon.

 

[sdowney717]

I only ever used green EG coolant, Did not use stop leak. I dont know but could it be rust and engine oil related goo?
Like from years ago, engine oil in the coolant? From a long time ago?

I would never have known it was coated like that unless I had taken it off to fix the drain plug.
Engine was not overheating.
Last year or so, this plug broke loose, It is a drain and for a zinc pencil.

I plugged it with PL as a temp repair, now boat is on the hard, I am fixing the plug which I silver soldered on. And I see that stuff in the heat exchanger.

 

[sdowney717]

What kind of coolant it was ? Raw water flows through the tubes?

Old Green EG.

Yes, raw water flows inside those copper nickel tubes. The coolant flows on outside of the tubes and is contained in the central and upper housing.
Ends of the heat exchanger hold raw water.

 

[BlueBell]

So, if it works, why fix it?

 

[sdowney717]

So, if it works, why fix it?

I don't think it should have that dirty coating inside it.

Now would be the time to clean it out.

It is like a soft gunky rusty colored hard grease.

IT is nasty looking.

 

[sdowney717]

I wonder if white vinegar will work, it's a cheap cleaner.

 

[sdowney717]

I recall now years ago I put some Bar's water pump lubricant in, and it turns the coolant whitish.
I do not recall ever putting in a stop leak, but I suppose I could have forgotten that.

I remember using Bar's stop leak in a car engine once, and it coated the entire inside of the cooling system with that kind of stuff!
Like a rubbery brown glue, and it clogged the radiator.

 

[sdowney717]

Bob is oil guy forum, guy recommends this for flushing out crap from cooling system
Does have a lot of good reviews.

Amazon.com: Irontite Thoro-Flush Coolant System Cleaner - Removes Rust, Scale, Oil, Sludge & Gelled Dex-Cool - 16oz Powder - Cleans Cooling Systems, Restores Coolant Flow, Safe for Cast Iron, Aluminum & Plastic : Automotive

 

[sdowney717]

I guess what I can do is try various things to see if it can clean it out.
May scrape off some gunk and test it against various cleaners.

Engine flushes won't work unless engine runs.

 

[montero]

If it's "soft gunk rust colored hard grease" I would use some organic solvent e.g. gasoline , than I will search what possibly causes oil contamination of the coolant.

 

[fallguy]

Go to a radiator shop; they boil it clean..

 

[sdowney717]

Avoid DIY Boat Heat Exchanger Cleaning & Save https://flushingservices.com/blog/Boat-Heat-Exchanger

Found this, which claims don't use acid cleaners. Don't take to a radiator shop.
Claim is acid will ruin it. Rad shop will kill it.
I was not planning on anything except a DIY job
It is copper nickel tubing and copper shell is thick. It is much thicker than a car radiator.
I can't see how rad shop acid cleaner that works on very thin brass radiators does not destroy them, if the claim is true.

 

[Rumars]

The right way of doing it is to remove the core and pressure clean the it and the shell. Of course this probably involves resoldering the caps, because whoever buildt it initially didn't think of diy maintenance.
Since I have a feeling you don't want to do that the only thing remaining is to stick the pressure cleaner wand into all the openings and hope for the best. Then hot water and soap and repeat until only clean water comes out.