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Pull the core - its not that hard.

(Drain the cooling system first!)

Go to Home Depot and get a bottle of Phosphoric acid. Its green in color, and is used to get rid of rust and such.

Take 5 gallon paint bucket (empty!), put in Phosphoric acid. Immerse core until the bubbling stops.

Take second bucket, dissolve a couple of boxes of baking soda in water. Remove core from first bucket, insert in second to neutralize acid. Leave for a few minutes.

Reinstall core, refill cooling system.

You're done.

PS: Check the rest of the raw water system. Its a good bet that the rest looks as bad, and will need the same treatment (e.g. gear cooler, fuel cooler, etc)

$2100 to pull and clean the cores? My, how big a wallet you have, Mr. Boatowner. I can do both of my engines this way in a day.

200F is too hot. Don't ever let a Detroit go over 190-195 - you'll cook it.

Yes, you can do it "in place."

HOWEVER, there is real value to tearing these down. You get to inspect them, which is valuable. Also, the bolts and end plates, seals, etc - all degrade. Don't take it apart regularly and some day you might not get it apart at all! Price out new H/Es (with cores - tank and all) and if you think $2100 is a lot of money.......

Also, the acid is not all that kind to seals. It probably won't cause trouble, but why take the chance, when you get value from doing it right anyway?

I do it out of the boat. Its cheap insurance and not hard to do. Just time consuming, at least the first time, until you figure out all the tricks on your engines (e.g. which order to take things apart in so you get the easiest removal, etc)

Go buy the gaskets (a few bucks an engine) and have at it. When you put the H/Es back together use RED Permatex on BOTH SIDES of the paper gaskets, and marine-grade grease (e.g. trailer bearing grease) on the bolts before you run them into the H/E tanks - this will keep them from seizing up on you down the road, and also keep the salt water from leaking on you.

On many Detroits there is a gland on the outlet side of the tank (essentially a big "O" ring) that seals the coolant and raw water sides from each other. Pay extremely close attention to that seal - both the O-ring and the sealing surfaces! If in doubt, replace the O-ring and if you don't like how the gland looks consider replacing it; if that seal fails you will likely lose coolant out the raw water outlet and not know about it until you overheat.

Don't neglect the gear coolers, and also consider replacing all the hose while you have it apart. I call transmission coolers "auxiliary sea strainers" for good reason - you'd be shocked at the amount of crap I've pulled out of mine.

I generally pull my coolers every couple of years or when I start seeing creep at cruise power. Its taken two years, and its also needed to be done in a bit more than one! While you're at it check the raw water pumps - particularly the wear plates and end plates to insure there is no scoring or damage, and the wear plate is not worn excessively.

Low raw rater flow for ANY reason will cause overheating as well.

Detroits have always been marginal on their cooling capacity. I live in Florida, and if I don't keep up on this stuff I have bad temperature creep problems and basically can't run beyond 1900 RPM or so on my 6V92s without overheating in the summer - but we get water temps in the mid 80s in the summer! If your water temps are lower you have a lot more margin to work with.

Karl, why would they advise him to have the cores shot peened? is this SOP, I've not heard of it. I will have this job to do on my Caterpillars this coming winter, they are long in years although not that long on hours. I did the aftercoolers, which are in the coolant jacket, last year, and they actually looked pretty good- the air circuit was gummed up but the fresh water side looked alright.

shot peening is used to increase surface hardness on metals and to stress relieve metal after machining or casting/forging processes. Shot peening would destroy a heat exchanger tube bundle. Maybe they meant bead or sand blasting. This is also bad for bundle. Acid, rods and a brush would be the safest approach for me.

Rufus

Sorry for the confusion. I did not realize there was a difference. Either way, sounds like it's not needed.

Radiator shop wants $100-200 for a boil & clean. I think I'll take the advice of others and pull the core and have it done properly.

I'd like to pull the fuel & gear cooler for a good cleaning this spring. Not sure how long it's been since last done.

Any tips & tricks I should be aware of? I think it will get messy when lines are removed. Same question for the oil cooler located at the bottom of the expansion tank.

Just a quick note that Phosphoric Acid is sold in various strengths and under different names. Phosphoric acid, when applied to ferrous metals converts any rust/oxide in the form of a ferric oxide (some techie can correct me) into a Phosphate, due to other chemicals in the mix. Be sure you know what strength you are working with.

Phosphoric Acid is found in various dilutions in Naval Jelly, EndRust, "Metal Prep", various soft drinks, and in straight bottles. When the rust cures at the atomic level, it turns blackish. Navel jelly also contains Sulphuric Acid.

The phosphate in the acid converts ferric oxide (Fe2O3) into iron phosphate (FePO4) and water in a faster simple exchange reaction:

Fe2O3 + 2 H3PO4 ® 2 FePO4 + 3 H2O

The water is removed when the part is cleaned but the iron phosphate will adhere due to surface effects so that it does not wash away.

Thats more than I know...

There are Material Safety Data Sheets out on this stuff. Of course Muriatic acid was mentioned above.