My brother and I just bought a 1979 El Camino that has been stored on the west coast for something like over 20 years. We got a good deal on it. It has a mild small block 305 that someone had installed a dual plane aluminum intake and Holley carburetor. We got the engine running after putting on a new fuel pump and it ran halfway decent but after a short test drive, it overheated pretty quickly. We decided it probably needed a new thermostat so we pulled it off. What we found was this nasty white crud all inside the water passage underneath the thermostat. We included a photo. We put water in the radiator so part of this stuff is mushy but other parts are like hard as concrete  What is this stuff and how do we get rid of it? Thanks,

N.D.

This is a great question.

We’ve run into this one before a long time ago helping a friend with a Camaro that he had found. It too had been stored for a long time and we found the same stuff inside the radiator. We asked our friend Jay Ross what this is and he said it is basically a gel that is formed when ethylene glycol anti-freeze—the original “green” colored anti-freeze—is allowed to sit in the cooling system for a long period of time.

When this occurs, the anti-freeze silicates tend to harden to form this gel. If you are lucky, the gel, as you mentioned, is soft and mushy and can be somewhat easily removed by draining the block and radiator and flushing the system. In our case with the Camaro, that stuff had hardened inside the cylinder head in the coolant passage next to the intake manifold. We removed the intake and managed to chisel that stuff out of the water passage in the head and vacuum it out on both sides.

Unfortunately, even if you remove all this corrosion, there’s no guarantee that it is not formed elsewhere in the engine or the radiator. In our case, once we thought we had the engine cleaned out, the engine still overheated. With the engine running, we took a handheld infrared temp gun and pointed it at various parts of the radiator. That’s when we discovered that the bottom third of the radiator was plugged with this same corrosion and not circulating water through that portion of the radiator. The gun showed the whole bottom third remained cool compared to the rest of the radiator.

Rather than attempt to clean the radiator, we elected to just purchase a new one. But before we did that, we ran some serious acid-based cooling system flush through the engine to clean out the engine. That caused more issues since the flush then also affected several steel freeze plugs that had seriously corroded and once they were clean, they leaked.

This required replacing all the freeze plugs with brass versions, including the two in the rear of the engine in the bellhousing area. This is a lot of work. This isn’t really difficult, but it is time-consuming. The good news is that with the old freeze plugs out, we could look inside of the block which appeared in decent shape with no blockage from this silicate gel.

The net result was we then had a relatively new cooling system. The key then is to protect his new system to make sure this corrosion doesn’t happen again. The main thing is to use a 50/50 mix of traditional ethylene glycol anti-freeze. You may notice that most anti-freeze companies now sell anti-freeze in pre-mixed, 50/50 jugs. But if you check carefully, you will notice that this pre-mix is only slightly less expensive than the same, full strength anti-freeze. So that means you are paying almost the same price for anti-freeze that is 50 percent water! So the key here is to only purchase the concentrated anti-freeze and mix it yourself.

You may enjoy this article too: How to Clean Your Cooling System with an Easy Chemical Flush

Another tip that Jay Ross offered us is to not use distilled water. When water is distilled, it removes electrons from the water. This makes the water “electron hungry” and will pull free electrons from soft metals like aluminum or magnesium. Ross suggests using soft water instead. This process removes the solids from tap water that can contribute to reducing the anti-corrosion additives in the anti-freeze. We know that anti-freeze companies often tell you to use distilled water, but it really isn’t the best. If you care about your engine, it’s much better to use soft water. Hard tap water is the worst so don’t use that unless you have no other alternative.

If you live in an area where freezing isn’t an issue, you can run soft water along with a bottle of anti-corrosion additive like No-Rosion or Hyper-Kuhl or other anti-corrosion additives to your cooling system. This will protect your cooling system for roughly a year or so and then will need to be re-fortified. This will keep the system fresh and minimize corrosion and allow the system to do its job of keeping your engine running at its optimal temperature.

thermostat for an engine cooling system gummed up with deposits
This silicate gel is nasty stuff and will require physical removal of as much of it as possible from the cooling system before you flush the system. You may have to use an acidic coolant flush more than once to eliminate all of this corrosion but the effort will pay off with a more efficient cooling system. (Image/Jeff Smith)

Keywords
antifreeze, coolant, cooling system
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Author: Jeff Smith

Jeff Smith has had a passion for cars since he began working at his grandfather's gas station at the age 10. After graduating from Iowa State University with a journalism degree in 1978, he combined his two passions: cars and writing. Smith began writing for Car Craft magazine in 1979 and became editor in 1984. In 1987, he assumed the role of editor for Hot Rod magazine before returning to his first love of writing technical stories. Since 2003, Jeff has held various positions at Car Craft (including editor), has written books on small block Chevy performance, and even cultivated an impressive collection of 1965 and 1966 Chevelles. Now he serves as a regular contributor to OnAllCylinders.