5 months ago

How to Diagnose and Fix Car Radiator Leaks

fix a faulty car radiator

The internal combustion engines that keep cars going are miniature furnaces. Temperatures inside the cylinders can reach well above 2,000 Celsius. If you need to keep the engine from disintegrating, you need something to cool it off. That’s where the radiators come in. Almost all modern-day internal combustion engine cars are water-cooled. 

What that means is there are channels of water around the cylinders in the cylinder block. Water is circulated through these channels, and then it gets sent to the radiator. The radiator, as the name implies, radiates the heat from the water, and then it is sent back to the cylinder block to cool it off. 

Radiators, just like any other part of the car, can break down and leak. If that happens and goes unchecked, the results can be catastrophic for the engine. In this post, we will examine how to diagnose a bad radiator, and how to locate and fix the problem inexpensively, at home with common hand tools. 

First Things First 

Here are some things that you need to be aware of before you start working on fixing a radiator leak in your car. 

  • A car’s coolant system is pressurized which can lead to the temperatures of the fluid inside it going well over the boiling point of water. That is a lot of heat and can burn you. 
  • NEVER open the radiator cap if the car is hot, no matter what. 
  • Engine coolant is poisonous for humans and other mammals. If you have to drain it, dispose of it responsibly. 
  • Do not turn on the engine when there is no coolant in the system. Even just turning on the engine for a couple of minutes without coolant can cause irreparable damage to it.
  • If you have any doubts about the quality or results of the repair you have performed, take the car straight to a professional before using it, or tow it if it’s heating up.

Signs of a Leaking Radiator 

The first step in repairing a leaking radiator is to diagnose the problem. Make sure that the radiator is actually leaking and find where the leak actually is.

If you have puddles of red, orange, pink, or green fluid on the ground where you park your car, this is most likely a sign of a leaking radiator as those are the colors of engine coolants. However, a greasy blackish liquid leaking from the car is most likely an oil leak.

Some leaks are so small that water doesn’t leak through them when the vehicle is parked. However, when the engine gets up to operating temperature, the increased pressure inside the system causes the water to ooze out. Such leaks are the hardest to detect. Here are some tips on locating them: 

  • Keep track of the coolant levels. If the coolant drops down a bit, that’s normal as it evaporates during normal operation. If the coolant keeps going below the minimum threshold, you might have a leak. 
  • If the car heats up at low speeds or when stationary in the traffic, that might be caused due to a coolant leak. 
  • Turn the engine on and get the car to the operating temperature. Ask someone to rev the engine while you carefully inspect the radiator and the hoses connected to it. If there is a minor leak, you can see water or steam coming out of it.
  • Inspect the radiator carefully; any signs of rust on it usually means that there is a small leak that causes water to come out when the system is at high temperature. 

How do you Pinpoint Radiator Leaks?

The best way to pinpoint the location of a radiator fluid leak is to use a radiator leak detection kit. The kits cost under $20 and consist of an ultraviolet dye and a torch.  

  • Add the dye to the radiator, making sure you DO NOT spill any on the radiator or anywhere else on the car. 
  • Rev the engine up so that the dye mixes with all the coolant and heat the system up. 
  • Take the car to a dark location and turn on the UV torch that comes with the kit. 
  • Shine the UV light over the whole radiator and all the hoses attached to it.
  • Water leaking through any hole in the radiator or any loose connection will bring the dye out with it, and it will glow under the UV light, making the location of the leak visible to you. 

You can also use this dye to detect leaks in the gasket of the windshield, even though it is not made for this. 

Types of Coolant Leaks

Coolant system leaks can be classified into four types:

  • Radiator leaking from the top or bottom plastic tanks
  • Leak in the hoses connecting the engine and the radiator
  • Minor crack in the metallic body of the radiator that only leaks under pressure
  • A major leak in the metallic body of the radiator

Of these four, you can solve the first three radiator problems at home. For the fourth, we suggest you go to a mechanic. You can replace the radiator to fix number four, but a mechanic can save you some money by welding it instead of replacing the whole thing. 

How do you Repair a Radiator Leak? 

If you have a car radiator leaking water and you have pinpointed the source of the leak, here’s how you can fix it depending on the nature of the leak.

Radiator Leaking From Bottom or Top Tanks

To repair the radiator tanks, you’ll need a plastic repair kit. Buy a high-temperature plastic repair kit online and follow the instructions that come with it to repair the leak in the tanks. These kits are inexpensive, and you can do this in just a few minutes.   

Leaking Hoses Connecting the Radiator to the Engine 

Most of the time, coolant leaks from the hoses that connect the radiator and not the radiator itself. To fix this, you will need to replace the hose. 

  • Find the part number on the hose and order a replacement or buy one at your local auto parts store.
  • Make sure that the car’s engine is not hot and drain the radiator via the drain plug at the bottom.
  • Undo the hose clamps on both sides of the affected hose and pry it off the connection points. This is the trickiest part of the process. Wiggle the house a little bit to make it easy to remove. 
  • Replace the hose and tighten the hose clamps to secure it and prevent any further leaks.
  • Use the coolant leak detection kit to make sure there aren’t any leaks in the joints of the hose. 

Minor Crack in the Metallic Body of the Radiator

These leaks are the hardest to detect, but the easiest to fix. All you need is an auto radiator leak repair powder or liquid. You can purchase these online and in all auto parts stores. Make sure it’s made for your radiator (steel, copper, or aluminum). 

Pour the product into the radiator to seal the leak. Keep in mind that these only work for really small leaks. 

Disclaimer: If you have limited knowledge of cars, consult a mechanic instead of trying to rectify the problem on your own.

Frequently Asked Questions

How do you tell if your radiator is leaking? 

The most evident sign of a leaking radiator is decreasing the coolant level in the car. If your coolant needs topping off every other day and yet drops down below the minimum level, this is a sign of a leaking radiator. Otherwise, puddles of pink, orange, or green fluid where you park the car are also indicative of a coolant leak.

Can you drive a car with a radiator leak?

Yes, you can, but we don’t recommend it. The car will overheat if the coolant level drops down below the minimum mark. The best practice is to fix or get the radiator fixed before it’s too late. 

Can a leaking radiator be repaired? 

Yes; in most cases, a leaking radiator can be fixed. If the leak is very small, you can use off-the-shelf products to fix it at home, and if it is a big one, you can get it fixed by a professional by welding. 

How long does a leaking radiator last?

This depends on the nature and size of the leak. The leak itself will not render the radiator useless, but your car will start overheating if it is left unchecked.

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