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How to remove lime scale inside my 37 Roadmaster engine


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Hi there again,

my 37 Roadmaster keeps on overheating. I checked the ignition timing, carb is overhauled and seems to be ok, spark plugs are light brown - as they should. Ingnition timing vacuum advance seems to work fine - as much as I could tell. Coolant is plain clear water, no anti freeze. So I believe I did the obvious.

Still, on uphill roads it doesnt take long until I am stranded with a boiling car on the curb side. Even in idle, the temperature doesn´t go down anymore (which is strage, as elsewhere the temperature never goes up in idle to this level).

Somebody told me that before I remove the radiator, I should try to eliminate all the lime scale and calcium deposits inside the engine block and cooling system by chemical wheapons.

He recommended to let the engine run with a quite strong and aggressive acid in the coolant for several hours and then flush with plain water afterwards.

Has anybody done this before?

What does it do to gaskets?

Is there a recommendation for the type of acid? - I was thinking of one that is usually taken by plumbers to clean old heating pipes.

Thanks as always for your helpful advice,


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I belive that Muriatic Acid is what the plumbers use to clean out rust and lime in heating systems. If your radiator is on the old side, I would be careful because you could end up with a bunch of leaks. Also, the fumes are not healthy to smell and could do dammage to you lungs. I never tried it in a car's block and cooling system, but have been told by others that does a good job of cleaning out radiators. I have cleaned rusty gas tank's with it and it works well for that. After cleaning the fuel tank I always seal them with a good tank sealer. Make sure you keep a garden hose handy to wash things down.

Thinking back about something else. Lye is what is used to tank engine blocks by machine shops.

This may be a good subject to post on the AACA general forum. Dave!

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As I have said many times before the only proper way to clean out a block is to remove the core plugs and physically remove the scale and deposits. And never ever run straight water. Always use 50/50 water and antifreeze. It lubricates your water pump, prevents corosion and has a higher coefficient of heat transfer. Change it every second or third year and never have overheating problems again.

I had two straight eight Buick's and got nearly ten pounds of junk out of the water passages on them. When I worked for GM in the late 50's and 60's we knocked the core plugs out of every Buick that had an overheating problem and solved it once and for all.

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With Tinindian I would have to agree. The best way is to remove the core plugs and remove deposits that way. It is unbelivable what comes out sometimes. I usually stick a high pressue washer (3000 PSI) in the Holes and watch the sediment fly! Dave!

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I would suggest this approach.

First weekend: take off your grill and hood. Pull the radiator and water pump. Make a flushing tool out of a garden hose end by brazing a brass fitting to it. Then flare a piece of 1/4 inch tubing, about 24 inches long and attach to the fitting. This will be a semi-flexible probe that you can snake into the block - through the front, where the pump was, and through the freeze plug openings. The pressure will be impressive! The amount of junk that comes out will amaze you.

Monday: Take the radiator to your local repair shop. He will flush it and pressure test for leaks. About $75.

Any evening just around dinner time: Using a pot on the kitchen stove, check the operation of your thermostat. In the housing, make sure the bypass works.

Friday: Pick up your radiator. Paint it Friday night, if this wasn't included in your $75! Don't build up much (if any) paint on the fins.

Second weekend: Put it all back together with new gaskets and hoses, where needed. Run 50/50, (or just less) for the sake of the corrosion protection.

I agree with the other guys, you will get a bunch of crud out. Also, muriatic acid will help this process. If you do this without pulling the radiator, I would be concerned that the newly loosened stuff will just travel to the radiator.


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Guest Andynator

You can get muriatic acid at any well-stocked swimming pool supply store. It is diluted hydrochloric acid. I'm with you though, I wouldn't be crazy about using it in an engine block.


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