Step 1: Locate the Source of the Steam
Sometimes you can easily see where the steam is coming from when you look at the radiator, and you’ll most likely see a pinhole or a ruptured seam. Before you do anything, however, you need to give your car some time to cool off so that you can open the hood safely. If you can’t see where the leak is coming from, then try washing down the radiator and hoses with water and start the engine again. As it runs, watch for the leak.
Step 2: Let the Engine Cool Off
Once you’ve located the leak, you will still need to allow some time for the engine to cool before you can touch it or remove the radiator cap.
Step 3: Repairing a Leak in the Radiator
You will need to find a way to temporarily plug the leak so that you can go get a more permanent fix. You have a few options, so use whatever you have with you or can attain the easiest from the following:
- Cold weld epoxy. This is the safest and most reliable option. Start by draining and drying the radiator so that you can apply the cold weld epoxy over the leak. Once you have done this, you need to wait for about two hours for it to dry before you fill the radiator back up with water and begin driving.
- An egg. While it may sound like a myth, one or two eggs can actually be used to temporarily stop the leak. When you crack the eggs and put them in the radiator, they will essentially cook in the hot water and the pressure of the radiator will force the egg into the leak.
- Black pepper. If you pour a spice-rack-sized container of pepper into the radiator, it will flow to the leak and harden, which will effectively plug the hole. Paprika, cornmeal and mustard powder are suitable alternatives.
- Commercial leak repair products. These products are available in most automotive parts and supply stores, but should be used as a last resort as they have been known to obstruct the flow of water through the radiator.
- Duct tape. Duct tape is one of the most important car tools you should have. If the leak is in one of the radiator hoses, then you can wrap duct tape around it for a temporary fix until you can purchase a replacement hose.
Step 4: Get to a Mechanic
A leaky radiator requires a permanent solution as soon as possible, but the above-mentioned fixes will be enough to at least get you to a mechanic. Anything that you have put into the radiator (eggs, pepper and so on) will get flushed out later when the repair is being made.