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My mother-n-law has a 1997 Dodge ram 2500 van with a V8 and it only has 63000 miles. The problem that she has is that the antifreeze went from the green color to a redish color. I took her van to a garage and had them do a flush. It didn’t take long for the antifreeze to become redish in color. I have personally flushed out her radiator multiple times and still it didn’t help. My questions are: What,if anything, can be done to stop the anitfreeze from changing color? What is causing this issues? Is the cooling system less efficient since the coolant changes to the redish color? Is she due for a new radiator? Thanks for taking time to look at my message and I hope to here from you soon.

Apparently the rust inhibitor in the old antifreeze wore out. It is the reason why antifreeze should be replaced periodically. Even though it still protects against freezing, it won’t protect against rusting. Modern antifreeze is formulated to protect aluminum from corrosion as well as cast iron parts from rust. Most cooling systems contain some of both.

How did the garage flush the system? If all they did was fill and refill the radiator a couple of times, they didn’t do an adequate job of cleaning EVERYTHING out. Once ALL of the rust is gone, filling it with fresh antifreeze should clear it up. If this is not done properly, rust will eat through the freeze plugs. The fix may be very expensive, depending on which freeze plugs rust through.

Thanks for you input. The garage used a evacuation machine to flush out the system. They did this process for over an hour. What is a freeze plug and where are they located? I have never heard of a freze plug.

If you want to do this yourself, flush not only the radiator, but the block as well. If you buy you antifreeze form a national chain auto parts store like Autozone, ask them to show you where the block drain is located. They should be able to show you on their computer screen. You can also go to their website and find it.

Normally I recommend that you just drain the block and the radiator, but in your case, maybe a garden hose flush might be a good thing. Make sure the heater valve is on full hot when you do this so that the heater coil gets flushed too.

When you refill, try using a 2:1 ratio of antifreeze to distilled water. Also use the new universal antifreeze, it may be green or yellow or even orange. Stick with a major brand, but any major brand will do. I recommend the one on sale. Avoid off brands. Use distilled water to avoid any mineral contaminants that might prematurely use up the corrosion inhibitors.

The heavier concentration of antifreeze will increase the amount of corrosion inhibitors.

Freeze plugs are round discs that go into holes in various locations in the head(s) and block. A long time ago, before ethylene glycol antifreezes became widely available, these plugs would pop out if the water in the cooling system froze during a long cold winter night up north. By popping out, it would protect the block from cracking under the pressure of the expanding ice.

Today, they are still in engines as that is one of the ports the sand gets out during the casting process, but they are still called freeze plugs. In the old days, they were located to protect the block, now they are located for the most efficient removal of casting sand, which often puts them in awkward and inaccessible places.