How to Find and Fix Leaking Radiators on Trucks

How to Find and Fix Leaking Radiators on Trucks

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A truck radiator leak repair can be a very tricky job. Many drivers, who find a slow radiator coolant leak, will often decide just to add some fluid and leave it, with the intention of taking care of it at a later time. Unfortunately, ignoring a heavy duty truck radiator leak can become a very costly decision if delayed too long or not watched properly.

Whether you have a semi-truck radiator, a heavy duty truck radiator or just your basic pickup truck radiator, you will need to keep your cooling system leak free to operate correctly. Even a slow radiator leak can cause an increase in temperature, create an air pocket and cause overheating.

Most of the time, a semi radiator leak is a tube to header leak up in one of the corners of the radiator. Another common problem is a tank leak at one of the connections or a seam leak. While the tank leaks can be slowed down a tube to header radiator leak repair is almost impossible to fix on the road and is best left to the radiator repair shop. The key to most Radiator leaks is that they will normally start slowly and show signs of seeping well before a complete failure. If you’re doing your truck inspections properly, you should be able to spot coolant leaks before they shut you down completely.

A radiator leak repair should be completed by a radiator repair facility, and we do not recommend trying to patch a radiator or doing a radiator leak repair yourself. We also understand that there are times when you will have no choice and will have to try to slow down or stop a radiator leak. Every driver should know the symptoms of a cooling system leak, the steps in finding a cooling system leak, and the basics in how to go about patching a cooling system leak.

Locating a Cooling System Leak

Radiator leak symptoms can be easy to detect and at times you can even smell an antifreeze leak. Any antifreeze leak smell is a sure sign of problems and while smelling a radiator or hose leak can be easy, finding the leak itself, can take some time and patience. You will need to check the whole cooling system carefully, and you will not be able to see into every area that may be leaking. You may have an internal engine leak, like a head gasket leak, or maybe you have a leaking heater core or freeze plug. In some cases, you might need to use a pressure tester to help you find the leak. Here are some steps to take to help you with finding a radiator leak.

  1. For safety reasons, plan to look for any leaks after the engine is turned off and has had time to cool. Your radiator is the hottest right after you turn off your engine. Let your vehicle cool down a little before sticking your face next to the radiator checking for leaks.
  2. While looking for leaks, check for drips on the ground, steam, corrosion around a tube, or fluid shooting out of the system. Check your radiator, hoses, clamps, thermostat gasket, water pump, heater hoses, by-pass hose, reservoir tank and your radiator cap. On another note, if you have a Ford truck radiator leak or a Chevy truck radiator leak, when your engine is cold, the leak may not even show up. Some leaks will only show themselves when the system is hot or under pressure. If you can’t find the leak when the system is cold, try a pressure tester. If that doesn’t work, you may have to have a certified mechanic check it while hot and under pressure.
  3. Once you have found the leak, keep checking the rest of your cooling system to make sure you have found all the leaks. Many times, we have found more than one leak on a vehicle. Once, we had a Dodge truck radiator leak that we were able to fix on the vehicle and after retesting everything we found a water pump leak, a thermostat gasket leak, and a leaky heater hose. Double check your whole cooling system after any repair. Fixing one leak and not checking the rest of the cooling system could get you back on the road heading for more trouble.

Fixing the Leak

The basic items you will need to fix a semi coolant leak can be found at most auto parts stores and should be included in a cooling system stop leak kit you can assemble yourself. This cooling system emergency kit would include; truck radiator stop leak, duct tape, rubber cement, an epoxy like JB Weld, hose clamps, hose splice fittings and basic tools. Remember, any on the road cooling system patch is a temporary fix with limited long term success. Slow the leak down and get in for service.

Before any DIY radiator repair is attempted, you must completely dry the area of the leak. You will need to clean off any dirt, oil, grease, paint or debris. You should also use a detergent or degreaser to clean the surface and then roughen the surface with a file or coarse sandpaper to provide the best repair.

  1. Cold weld epoxy; You can use a cold weld epoxy applied precisely according to directions after everything has cooled down and cleaned. JB weld has stopped a lot of leaks, and many drivers keep a tube of JB in their toolbox at all times.
  2. If you have the tools and the know-how, you can try to solder the leaking portion of a copper and brass radiator. Soldering a radiator is not an easy fix and requires flux, acid, solder and a very clean surface with the right amount of heat, at the right time, in the right spot. Adding heat to a corroded radiator tube often causes a more profuse leak to an already weakened area of the radiator.
  3. Aluminum radiator leak repair can be attempted using products from many companies with varying success. Stic-Tite aluminum radiator repair sticks are one of the easiest products to try, but it all depends on the condition of the radiator and the preparation of the surface you are trying to repair. You can check out aluminum repair materials from Northern Factory Sales or Johnson supply with the link below.
  4. Radiator leak additive, more commonly known as radiator stop leak, is not advised unless no other option is available. If you have a water pump gasket leak, or a hard to get to radiator leak, stop leak may be your only choice and some leaks cannot be slowed in any other way. Using stop leak can cause other problems within your cooling system and should only be used as a last resort. In an emergency situation, on the road, using stop leak may be the best choice for your situation. We have found over the years that the best stop leak for us was Spot Weld by the Barbee company. We called this stuff “radiator man in a can.” In the right situation, it works as good or better than anything else, and we have even slowed down head leaks with this stuff. Click the link below to check it out and keep some in your shop.
  5. Duct tape is great stuff, and if you have a hose leak, you may be able to use duct tape to slow it down and buy some time. Check out our leaking radiator hose article for more information on truck radiator hose leaks.
  6. Some truck drivers have slowed down or even stopped a leak by removing the pressure within the system. You can do this by loosening your radiator cap to the first notch or removing the rubber seal from the cap. This will let the pressure escape and is not recommended except in an emergency. This action can aid in slowing down a high-pressure leak in the cooling system. Take note that you do take a chance of fluid being pushed out and worse overheating without the pressure on your system. If you remove or adjust your radiator cap, you must be aware of any fluid loss and your vehicles temperature at all times.
  7. Always watch your temperature gauge and fluid levels right after any cooling system repair to make sure everything is working properly. We recommend checking your system twice after any repair or flush.  If you have a leak and running hot turn off your A/C and turn on your heater. Your heater is like a little radiator and will help keep your system cool, even on a hot day in traffic.

Remember, any DIY radiator patch or on the road cooling system repair should only happen in an emergency situation. If this does happen to you, get your vehicle to a repair shop as soon as possible and have your complete system checked.

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