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Flushing rust out of engine block


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Last year when I had my engine overhauled, my rebuilder filled the water chamber with water and muriatic acid as the chamber was caked with rust.After letting the block soak for some time, he power flushed it with a pressure washer and then sent it out to be washed.

After the engine was done and it was running for several hours, a lot of "unseen" chunks broke loose and clogged my radiator. I removed the water jacket covers, water pump, thermostat housing and inside there was chunks every where. I flushed it again with a pressure washer and ran Prestone rust flusher through the block for about six hours and flushed out the block again. It's better. The radiator has lost a lot of flow no matter how many times it is flushed out. Luckily I found a replacement radiator.

I would like to flush the block again with something a little more harsh thus give me a better cleaning than the Prestone before I install the good radiator. Any ideas would be much appreciated.

Thanks

Dan

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It's too bad your engine rebuilder didn't do it the right way and send the block to a chem-strip type of place for professional stripping. This is especially important in pre-1950 engines, which were run on water and alcohol, or just water depending on where in the world you live. The chem-strip process uses an alkaline chemical with electrical current passing through it. The crusty cooling passenges you see when you take your block (and heads and pans and manifolds, etc.) come back completely clean. The cast iron is a bright silver color rather than the dirty gray when the block is just hot-tanked at the local auto parts store. I get the block (and other non-moving engine parts) chem-stripped then the minute I get back from the chem strip place I final-clean everything with lacquer thinner and compressed air then paint all rough-cast areas with epoxy primer, inside and out, especially the cooling passenges. I have taken engines that were nothing but overheating trouble and after the rebuild they start up, come up to rated (by the thermostat) temp and stay there, no matter what. If you do this, and you have taken steps to know that you have a good, clean radiator you can do the impossible--drive the car at road speeds then get in a parade.

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Guest martylum

Sorry to hear about your problems with engine rusting in the cooling passages.

When i disassembled a 36 Lincoln K V-12 engine and removed the core plugs, each of the 6 cylinder jugs was entirely filled with rust particles as the engine was stored dry for many years.I wondered if there would be anything left of the cooling passages with all this rust but jugs are hard to find for these engines so I had an immersion cleaning outfit electrolytically strip the inside of each jug which cleaned out all the rust but also made some dime sized holes in the outer wall of 1 jug.These holes not there before the cleaning. i then had the jugs sonic tested for wall thickness in the valve and cylinder areas. After a good sonic test on the internal walls, i welded up the holes and rebuilt the engine. it runs nicely and stays pretty cool for a 30s engine on warm days.

I'm not sure anything less than a strip of this type will do the job on your block. Muriatic acid might take away away too much of the internal metal passages as it's not selective at eating away rust versus metal.

I'm currently working a a 53 Buick engine which sat for many years wet-it too has a lot of crud in the engine passages and I'm planning on a strip to minimize chances of corrosion working it's way into the rad. core later on. The acidic condition in the coolant ate away the radiator core to the point it needs replacement.Note---This cooling system was filled with antifreeze while stored.

Good luck on your repairs.

Martin Lum

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Mrpushbutton, how can you prime and paint inside an enine block where you can't get to most of the surface areas? At least mine you can't. The one side of my engine has the water jacket covers and once removed you can have full access to that side of the chamber but the other side is not accessible. By the way, when my rebuilder was done flushing the block it look like bare metal to me but obviously there was probably still rust on the other side that we couldn't see.

In any case, some one recommended a filter after the thermostat housing and before the coolant enters the radiator. This sounds like a great idea.

Do you have any recommendations as far as products to use to flush out more and what can I use to stop the rust from further developing?

Thank You Again

Dan

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I do just fine. For the cooling passenges I tape off the freeze plug holes, pour in an ample amount of primer and rotate the block on the stand, several 360 degree revolutions, then lift it by the front end with the cherry picker, move it around in that position, set it back down, lift it by the back, repeat. Then back on the stand, drain off the excess primer and daub up any excess that settles and you are done. I know several prominent restorers who will only do an engine this way.

I don't know any "magic in a can" that will undo 78 years worth of corrosion and crud. Bordens #7 used to make a powered acid mix that worked OK with a 20 year old car that had been neglected, all kinds of brown came out when you backflushed.

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Guest simplyconnected

Two questions, John.

Is the epoxy primer a HIGH TEMP paint? Cylinders get hotter than the coolant; I'd hate to see flakes of paint in the rad later on. I guess the big caution is to make sure the metal has NO rust before painting.

About how much and what brand of paint did you use in each freeze plug?

Aside from that, I have used muriatic (hydrochloric) acid on rusty parts and cast iron with great success.

Have LOTS of water handy! This is very hazardous and should be handled with extreme care and knowledge. WEAR GOGGLES and work OUTSIDE. These fumes are bad and will make everything in the surrounding area rust.

When the acid is HOT (140F), 10% mixed with water works fast eating up rust, and leaving the iron alone. That's what we use to pickle steel. They immediately wash with water and apply rust inhibitor oil.

Most restorers don't have facilities to do it right so they send their block out. Rusty bolts, springs, etc. come clean very fast.

Dave

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I use DP-90, that's what my friends use, it's high-temp all the way. We were doing this in the late 80s-early 90s, this isn't a new idea, and to date I know of no failures or problems with the epoxy primer coming off of the block, either in the crankcase or cooling passenges. It is very important to note that this is only recommended if the block has been chem-stripped. No acid or metal prep is necessary if you get it painted right after you pick it up from the strippers--as I said earlier I drive the goods from the strippers to the shop and get it painted that day. Then I send the block and heads out for machining.

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