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Reviewed by on Nov 01, 2019To ensure our content is always up-to-date with current information, best practices, and professional advice, articles are routinely reviewed by industry experts with years of hands-on experience.
Soldering iron
black tie wraps
acetone
tooth brush
hair dryer
screwdriver
marker or tape
Soldering iron
black tie wraps
acetone
tooth brush
hair dryer
screwdriver
marker or tape
Plastic radiator repair is performed at most auto body shops, but you have to pay for expensive labor. Fixing cracks in your radiator is a relatively quick and easy job, and you will save on your hard earned cash by simply locating the crack, preparing the area, and fixing the problem yourself.
There are various parts of the plastic radiator that can leak: you may spot a crack on the hose or the body of the radiator itself. Before you get to the actual repair, you may want to examine the fittings that lead to the radiator. In case the leak is coming from the radiator, put your old clothes on, roll up sleeves, and follow the steps below.
Step 1 - Locate the Crack
The easiest way to locate a crack in the radiator is to let the engine run until the temperature is normal high. It will take at least half an hour before pressure builds up. Shut off the engine so that the pressure forces out the coolant from the crack. Mark the cracked area with a marker or tape. Then wait for the tank to cool down and take the cap off.
Check if the crack is above or below the coolant level. If it is situated below, you have to drain some coolant until the crack shows up above the coolant level. You may remove the lower hose clamp or use a drain tank cylinder to drain the radiator tank. Make sure that you have new coolant to add once you finished repairing the crack.
Step 2 - Prepare the Crack Area for Repair
The next thing you need to do is to clean the crack with a toothbrush and dry the area. Pour a little acetone over the toothbrush and begin to scrub the crack and its surroundings. Continue scrubbing until the area is dry and no moisture reappears on the surface once the acetone dissipates.
Use the hairdryer to finishing drying the area, holding it close to the crack. Moisture will resurface again, and you will have to keep blowing over the crack until the place is completely dry. Scrub and dry the area one more time.
Step 3 - Proceed With Actual Repair
Press the tip of the soldering iron against the tie until it begins to melt, working as a sealant. Press the tie so that it wraps into the crack. Then, slowly move along the cracked area, ensuring it melts well enough to seal the crack. Keep melting at one place until the tie and its adjacent areas turn into a hot liquid.
Continue until you have melted the entire crack, wait for the liquid to harden. Cut off all unused portions of the tie. Now, you may fill the radiator with coolant and complete a test to make sure that the crack is properly sealed.
As you can see, all it takes is your new found knowledge and a little elbow grease to fix your cracked plastic radiator yourself. Now you can use your big savings for your next DIY project!
If your car radiator has a small leak, you may be wondering if it is possible to repair a plastic radiator and fix a radiator leak. Afterall, there is high-pressure, high-temperature coolant in the radiator tank. You may ask yourself, "How can a radiator epoxy adhesive possibly hold up under those conditions?" The answer is that it probably can't. It may fix the radiator leak temporarily, but over time, the radiator adhesive will, more than likely, come off.
If you take your car to a radiator repair shop to repair a leaking radiator, you will often find that they will repair metal radiator tanks but NOT repair plastic radiator tanks. Instead, the radiator repair shop will probably try to sell you a replacement radiator. The replacement radiator cost can be very high compared to just repairing something so minor and easily repairable.
Radiator tank repairs are not difficult at all. Just keep in mind a few things when you are repairing a cracked plastic radiator tank. First, the repair has to withstand high operating temperatures (200°F or 94°C and up).
Second, the repair has to contain hot, pressurized coolant, making it immediately obvious when your weld is less-than-perfect. Because of the harsh operating conditions, the radiator tanks are made from glass-reinforced nylon, a plastic that features a high-softening point. The high-softening-point nylon plastic is what helps the plastic radiator tank withstand the pressure and temperatures involved.
Adhesives don't stand a chance in such an environment. There's no way an adhesive bond can hold on over the long run at such temperatures with high-pressure water behind it.
The only true way to patch a plastic radiator tank is with a true fusion weld. The Radiator Repair Kit enables you to melt pure nylon fill material directly into the base material, creating a seamless, strong repair that will last for the long haul.
Creating a durable weld repair is not as easy on the radiator as it is on other plastic parts because of the high melting point of the nylon and the harsh operating conditions. However, by following the simple step-by-step procedure we have outlined here, you will be making quality repairs in no time.
Plastic Radiator Repair Video
Step-by-Step - How to Repair a Plastic Radiator Tank
Step 1
If you are repairing the radiator while it is still in the car, drain the antifreeze until the level of the antifreeze is below the crack line. This way, the antifreeze won't seep out of the crack and ruin the repair. Clean the cracked area with Super Prep Plastic Cleaner.
Step 2
If you have a heat gun, you can speed up the repair process by softening the plastic. Preheat the area to be welded with a heat gun. Heat slowly until the area in and around the v-groove begins to turn glossy. On long cracks, preheat a two-inch section at a time and complete the weld in that area before moving on.
Step 3
Melt a V groove along the crack line with the edge of the welder tip.
Step 4
Melt the Nylon rod into the v-groove with the airless plastic welder. The rod should come out melted and a little bit brown, but not discolored too badly. The fumes are not very pleasant, so work in a well-ventilated area.
Step 5
After depositing the nylon rod into the v-groove, remove the rod from the welder tip and use the welder's to mix together the new plastic with the radiator plastic. Keep mixing until the plastic is all one color. You need a good mix of the existing plastic and the new plastic to get maximum strength.
Step 6
Allow time for the plastic to cool and resolidify. Repairing radiators will save you a lot of money compared to a replacement radiator.
Another Radiator Repair Example
Here is another plastic cracked radiator repair. The same methods are used here. We are showing it to reinforce how simple it is to fix a radiator.
Step-by-Step - How to Repair a Plastic Radiator Tank
Step 1
If you are trying to fix the leak in the radiator while it is still in the car, drain the antifreeze until the level of the antifreeze is below the crack line. This way, the antifreeze won't seep out of the crack and ruin the repair. Clean the cracked area with Super Prep Plastic Cleaner.
Step 2
If you are trying to fix the leak in the radiator while it is still in the car, drain the antifreeze until the level of the antifreeze is below the crack line. This way, the antifreeze won't seep out of the crack and ruin the repair. Clean the cracked area with Super Prep Plastic Cleaner.
Step 3
Melt a V groove along the crack line with the edge of the welder tip.
Step 4
Melt the Nylon rod into the v-groove with the airless plastic welder. The rod should come out melted and a little bit brown, but not discolored too badly. The fumes are not very pleasant, so work in a well-ventilated area.
Step 5
After depositing some melted nylon into the v-groove, remove the rod from the welder tip and use the welder's heat to melt the rod and base material together until the weld area is the same color as the rest of the tank. Mix it well so that you get good inter-mixing of the rod and the existing plastic. This is how you know you've got a good fusion weld.
Step 6
Wait for the plastic to cool and resolidify, and you are finished. Repairing radiators will save you a lot of money compared to what a new radiator costs.
Plastic Radiator Repair Procedures
Here is how confident we are with the Radiator Repair Kit.
Radiator Repair Video
Drill a Hole
Polyvance’s radiator repair kit allows you to fix a leaking plastic radiator tank. To show how confident we are with our Radiator repair kit, we drilled a hole in a perfectly good radiator.
Crack the Plastic
Not only did we drill a hole in the radiator, but we cracked the radiator tank with a chisel.
V-Groove along the crack line
Before you start repairing, you will need to drain the radiator until the coolant level is below the hole. Create a V-groove along the crack line about two thirds of the way through the thickness of the plastic. You can either melt in a V-groove, or you can use a rotary tool and grind a v-groove like we did here. Be sure to round of any sharp edges.
Soften plastic with a Heat Gun
Plastic radiator tanks are made of nylon which has a very high melting point of about 425°F (218°C). While it is not required, the repair will go faster if you pre-soften the plastic with a heat gun.
Melt in new material
Melt the Nylon rod into the Vee groove with the plastic welder. The rod should come out melted and a little bit brown, but not discolored too badly.
Mix the new plastic with the old plastic
While the melted rod is still hot, use the tip of the welder to stir together the new plastic and the radiator plastic. Keep mixing until the plastic is all one color. You need a good mix of the existing plastic and the new plastic to achieve maximum strength.
Test Results
The car was started and run for 45 minutes with no signs of leaking.