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Descaling or derusting engine block

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Hi Guy's, Can anyone please advise the best way to descale the water ways in an engine of a 1920's Dodge. The car had been mostly restored and then placed in storage for many years. When finishing off the restoartion I found the engine had a blown head gasket. The head has now been removed and professionaly cleaned. The engine is fully assembled and still in the vehicle and apart from the head gasket problem, I can't see any reason to remove the engine from the frame, the running gear restoration appears to have been done to a high standard. Now I have noticed the water ways in the block are badly choked with rust and scale. I have attempted to clean out as much as possible with a piece of wire and a small tube connected to a vacuum cleaner, then blowing out the water ways with pressed air, however a lot of scale and rust remains.

Is there some type of chemical solution I can pour into the water ways and let stand for a while that will desolve the scale and rust ? Then maybe suck out and rinse with water and then dry with pressed air before reassembling. Regards - Ted

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I used Muratic Acid (buy from pool cleaning supply locations) to clean out my water jackets, but my engine block was bare and on a stand. I also use it for cleaning scale and any other rusty steel parts. I keep 5 gal containers for doing such stuff. There are lots of precautions when working with that stuff though!

Use a respirator, rubber gloves, goggles etc.

use in a well ventillated space

Keep vapors away from anything else in the vicinity you dont want to start to rust after exposure

Will deteriorate aluminum copper and other metals, but is ok on rubber. (isolate from radiator, aluminum water pump housings, etc. or anything else NOT steel you want to clean)

Rinse thouroughly and dry afterward. Apply paint or coat with corrosion preventer of choice or will flash over with rust rapidly.

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G'day Ted.

I had a similar problem with my Dodge (1930 DC 8 Cylinder). The amount of scale in an engine block is incredible. In my case the scale in the cylinder head had clogged most of the waterways and the radiator.

My suggestion is to remove the Welch plugs and continue like you are doing with the wire. Taking out the plugs gives better access. Also tap the block with a light hammer while completely dry. This will free up additional scale. Clean out with a vacuum cleaner and/or compressed air. The final step is cleaning out the block with a heavy duty water pressure cleaner. It will be more successful doing this while the cylinder head is off. Take care to seal around the valves so water doesn't get into valve guides and valve chambers but spray with WD40 or similar on completion.

On reassembly install a filter in the radiator hose. Suggest replacing plugs with steel and not brass. Galvanic reaction between different metals can lead to further corrosion and scaling



1930 Dodge Bros DC8

1961 Morris 850

1973 Land Rover 6 Cylinder Series 3 ex military LWB

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I would suggest the product called Evapo-Rust. It is a non-acidic and non-caustic product. Check them out at www.evaporust.com . I had never heard of it until I was faced with the same situation earlier this summer. I purchased it at their website.

I am in the process of detailing the motor on my 1927 DB Series 124. The car has sat idle for 14 years, and the cooling system had drained dry. When I pulled the head, I noticed a fine rusty powder inside the water jacket. I played with the "wire" and a "homemade adaptor" for the shop vac. That never seemed to get enough of the fine rusty power out to suit me. I knew good and well that there were a lot of nooks and crannies out of sight which I'd never be able to get to. I was in a position where I didn't want to pull the engine, nor was I able to able to flush the engine. I fabricated a garden hose assembly to bolt to the water pump studs at the rear (low end) of the block. I then gently poured several quarts of Evapo-Rust in the water jacket. (In hindsight I think I maybe should have diluted the product first.) I then let it sit for almost a month. When I drained the block, it it came out pitch black, and then I slowly added fresh water in through the top of the block. At a cup at a time I passed about 20 gallons of water through it, and it continued to run black, but it slowly cleared. During the flushing effort small flakes of black "stuff" would come out, but when put between my fingers they just dissolved away to almost nothing. No hard flakes. I repeated this process with the remains of a partial quart. I think there is still some loose black particulate matter in the block. When I get the head back on I plan on doing some pressure flushing with a garden hose before I install the water pump and the radiator.

Give this a try.

M.R. Simpers

Cocoa, FL

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  • 1 month later...

Thanks Guys for your replies, your suggestions were exactly what I was looking for, I will proceed with caution and I am now confident I will get the water ways clean without having to remove the block from the Vehicle. Thanks again and happy motoring. Regards - Ted

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