Engine Radiator Repair – What You Need to Know

There are many different ways that radiators are “repaired,” but not all methods are good for the radiator. In case you want to repair it yourself or are just curious about how it’s done, we’re going to share how we repair radiators.

Before we begin, it’s important to know the difference in types of radiators, particularly those made with copper-brass and those made with aluminum. Aluminum radiators cannot be repaired like copper-brass radiators can. Additionally, the type of tanks and the location of the leak is important too. Let’s review a few preliminary steps you need to take before you do anything else.

Identify the Material

Your radiator is most likely made with either an aluminum or copper-brass core. The tanks can vary and will usually be aluminum, plastic, or brass depending on the material of the core. What material the radiator is made from will determine how to best fix it. Some can be repaired while others need to be replaced.

Identify the Leak

This may seem like an obvious step, but it is important to know exactly where the leak is coming from. If you’ve noticed antifreeze on the ground, then you need to find the exact source. If it is a radiator hose and not the radiator itself, that’s a much easier fix. Some common failure points include any of the following:

  • Tank Connections (weld, bolt on, etc.)
  • Radiator Tubes (long narrow tubes that run the length of the radiator)
  • Header Plates (the tubes run into these plates and the tanks attach to them)

Besides the location, you need to determine why the leak is happening. Certain damage can’t be repaired and will require the radiator to be replaced. You should look for any of the following:

  • Significant damage to metal (tears, large holes, bulging)
  • Pinhole leaks (you may not see a hole but will see the coolant coming out)
  • Separation of tank from core
  • Obvious corrosion

Any kind of serious damage to the radiator means you will need to replace it. If the tanks are in good shape, you may be able to have the unit re-cored. Even with pinhole leaks, you should consider at least re-coring the radiator because it means there is corrosion taking place inside.

What You Should NOT Do

We’ve seen and heard a lot of different ways to “fix” a leaking radiator. Some of these may work to get you by in an emergency, but none of them should be considered a long term fix. Here are a few of the methods we have heard of that you should avoid:

  • Cut and crimp a busted radiator tube – While this could help in an emergency situation where you still need to be able to drive your vehicle, the fact is you are reducing the radiator’s ability to cool by doing this. The coolant has to flow through the tubes in order to cool the engine and the pressure has to be regulated as well. Doing this can increase the pressure in the cooling system and cause other weak points to fail as well as cause over-heating issues. You also run the risk of damaging other tubes and the fins when getting tools around the problem tube to cut and crimp it.
  • Add pepper to the radiator to stop pinhole leaks – You don’t want any foreign substance in your coolant. The coolant flows through your engine carrying with it any debris that has found its way in. The person who suggested this even said you’d have to add more pepper after turning off your engine, which just shows that this really isn’t a fix at all.
  • Patch weld an aluminum radiator – This one tends to make people angry since it seems like welding should fix most metal issues. The problem is not with the weld not holding but the fact that the metal has already fatigued to the point where it needs to be replaced. Even if the patch holds, other areas will fail. We’ll talk a little more about metal fatigue in the next section.

What Can and Cannot be Repaired

Aluminum radiators cannot be repaired like copper-brass. As an aluminum radiator is used, it begins to suffer from metal fatigue. As the unit heats and cools, the metal expands and contracts causing it to weaken. It’s similar to what happens if you unwind a paper clip and bend the metal back and forth. Bending it becomes easier and easier until it finally breaks. This is why repairs on aluminum radiators do not last. Even if you weld a damaged area, the metal is still weak and will fail again. We do not recommend repairing aluminum, instead we encourage you to have the unit re-cored with the current tanks (if they are in good shape). Otherwise, you should replace it.

Any time your tanks become damage you should replace them. They are crucial for your radiator to function properly and you don’t want to take the chance of a repair not holding or unseen damage/weakness causing additional problems later. If the damage has left pieces of the tank in the radiator, then you should also flush it out completely to ensure all the debris is removed. If you can’t remove the debris, then you will need to replace the radiator to prevent serious engine damage should the radiator fail later.

Copper-brass radiators are really the only ones that can be repaired effectively. Due to their construction using solder, they can be taken apart, cleaned out, and re-soldered. Obviously this only works if there is not significant damage to the unit. If you have leaks around the header plates or where the tubes enter the headers, then having the radiator cleaned and repaired will be an effective fix. Keep in mind that while copper-brass can be repaired, their construction also means they will need to be cleaned and repaired rather frequently. These units suffer from what is called “solder bloom.” The basics of this phenomenon is that due to the different types of metal used (copper, brass, and the solder) build up occurs around the solder that holds the tubes in the headers. This can eventually block flow through the tubes causing a build of pressure which can lead to burst tubes and overheating. There is no way to prevent solder bloom.

How to Avoid Repairs

As they say “an ounce of prevention is worth a pound of cure.” One of the easiest things to do to avoid needing to repair a radiator is to change out the coolant at the recommended intervals. There are corrosion inhibitors and other protective additives that break down over time. Even though the coolant will maintain its ability to transfer heat, the inside of your radiator and engine may suffer from damage by the loss of these additives. This is why changing the coolant is so important and will help your vehicle last a long time. Also, a regular cleaning of copper-brass radiators to remove solder bloom will help extend their usable life span.

How to Clean and Repair a Copper-Brass Radiator

These are the steps that we take when someone brings in their copper-brass radiator for us to fix. While the process is straight forward, it can be very time consuming and requires some skill when it comes to soldering the unit back together.

  1. Inspect for damage – Obviously any significant damage will mean that the unit needs to be replaced, but we also check for any leaks
  2. Chemical bath and flush – We use a chemical bath to remove any paint that is on the radiator and flush out any debris
  3. Cut off tanks – The tanks are removed, inspected for damage, and all old solder is removed
  4. Rod out the tubes – Using a narrow rod we push any build up and debris out of the tubes to ensure proper coolant flow
  5. Clean and solder the headers – Using a wire brush, the headers and tube joints are cleaned of all old solder and then re-soldered
  6. Attach tanks – The tanks are reattached and soldered
  7. Test for leaks – The unit is tested for leaks to ensure everything has been fixed
  8. Paint it – The final step for a copper-brass radiator is to paint it so it won’t turn green

Some of this you can try yourself; however, the chemical bath requires very dangerous chemicals that you should simply avoid. In addition, if you do not have a lot of experience with solder, then you should not try to re-solder the unit yourself as it takes a bit of skill to ensure a solid finish. The paint we use is a special paint that won’t insulate the radiator like a lot of others. After all, there’s not much point in fixing a radiator if it can’t transfer heat because the paint holds it all in.

As we said before, copper-brass radiators are the only ones that can be effectively repaired. Other radiators should at least be re-cored if the tanks are good. Otherwise, they should be replaced with a new unit. If you’re unsure of whether your radiator can be repaired or not, give us a call and we’ll help advise you on what you need to do.

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