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How To Repair A Car Radiator Leak In The Plastic Area? ? ? ? ? Answered

I have a radiator leak that I want to repair instead of replacing the whole radiator. I tried a couple of 2 parts epoxy glues and it won't hold for long. I think the heat just makes it weak. They are small leaks(2) on top of the plastic area. I was thinking maybe trying some fiberglass resin and cloth since I have some leftover from my fibeglass speaker box I've done a while back but not sure if I should go that way. Anyone knows of another way? Anyone had this problem and got a fix? or if there's a website where I can get the top piece to replace it myself please post a link. It's a 2000 dodge neon. Thanks.


I used Sugru moldable glue on the radiator on my 2000 BMW when it developed a leak. I did it about 2 years ago and didn't leak a bit until lasted for more than 25000km. This is super impressive in my opinion. The leak had developed due to ageing of plastic around the region. I got rid of the aged plastic and moulded the area with Sugru. This definitely works.


4 months ago

how can i clean the inside of my radiator my self?

You can buy radiator flush kits at most auto parts stores and I think Wal-Mart carries one too. You can buy a radiator flush solvent that you add in and then flush out (Ithink you need to run the engine for a bit but it's been a while). All you need is a garden hose and you will need a way to form a pretty good seal around the hose and the radiator fill spout. Without the kit that has a cap you can screw the hose on to you could, in a pinch, use some duct tape. It doesn't have to be an air-tight seal. You just want some decent water pressure. Here are a couple of links. There are definitely more products out there, but this should give you an idea of what you will need.




what jb weld do you use? as have just read comments and searched to buy it but there are many! i have a 1cm split in the very top of the plastic on my radiator

SEAL ALL is the product you are looking for "SEAL ALL-Gas and Oil"

My 1998 BMW radiator blew a hole in it when my car overheated after the serpentine belt slipped off the idler pulley, JB Weld would not bond well to the type of plastic, however JB Weld stick done in layers will, just sand the area first and clean it will alcohol, my repair held up for nearly a year before starting to leak again. Another more expensive option is to plastic weld it which is a permanent repair when done properly.



Hi. I just had the same problem with my plastic radiator top yesterday on a Nissan car. Also had this problem on my other car a few years back. My trusted mechanic just molded aluminum copied from the plastic top, welded it to the radiator body. it worked like a charm on my other car, and so as with this one from yesterday. I was made to choose between copper and aluminum. My other car's radiator top was molded from copper, it has good heat transfer but tends to warp but still holding for 7 years now. I opted using aluminum yesterday on my nssan car to address the warping. All was well. By the way I am not from your country. I just sharing what I did, which cost quarter the cost of getting an original manufacturer replacement plastic part.

I agree with these guys for the most part but when we were running race cars and Everytime we got a leak in the radiator we would clean the area and mix up some JB Weld about 30 to 40 percent of hardner and to 60 to 70 percent of the sealer and take a file and file into the crack to open it up a little bit and then clean it one more time and then push the JB Weld into the crack with our fingers to push it in deep and spread it out all with the motor still very hot . If you push it in the crack at that mix while the motor is still very hot that mix would harden slowly about the same time it takes the motor to cool down. With the mix hardens slowly with the motor cooling slowly as the crack closes slowly that forces the mix into all the open spaces in the plastic and then they both harden at the same time and let it set for 24hrs and that radiator lasted the entire season and for at least 2 more seasons after that unless we tore it up in a crash but as far as the leaks in all of the ones we fixed that way we never once had to redo any of them and those cars ran with very high pressure and they got very very hot many times so that is how we did it so its up to you on what you do but as for us we were winners many many times with the very radiators that we fixed that way. However you do it I wish you all the best. D

So the motor has to be hot? I think I'm gonna try this I got a 1990 Ford Taurus and a new radiator is gonna cost $100.00 that I don't really have,Thanks!

I had 2” long crack on plastic top of radiator of 1999 Toyota. I tried JBWeld and other brand of putty but they do not work on plastic surface. I purchased “Permapoxy 5 minutes Plastic Weld” for $7 from Advanced Auto Parts. It took 10 minutes to finish the job and it completely sealed the leak. It is a great product.

Thanks,I'll try it! I too tried JB Weld but when it got hot it just peeled right off.

When you apply this product, apply it generously to be sure and wait few hours to before you start the engine. Once it is cured it becomes solid plastic that won"t melt up to 250F.

tokiodude stop supporting the more expenisive stuff get your materials right and go back to school, and don't lie. "Original J-B Weld can withstand a constant temperature of 500º F. The maximum temperature threshold is approximately 600º F for a short term (10 minutes). Refer to individual product packages for more temperature information"

Clean the area good then use some rough sandpaper over the area real good to give the mix more to grab ahold of then clean the area again very good, then when you put the mix in it try pushing it into the hole so to make sure u fill the entire crack or hole. You must let it set for at least 24 hrs before putting it back into service. Oh yea the radiator must be at least at operating temp because when the material is hot the crack will open up more and as it cools down the crack shrinks closed. If you get it as clean and as hot as possible you should have no problems....best of luck to ya

Thats good to hear and the main thing is that it worked and is not leaking anymore, and yes that Permapoxy plastic weld is a great product too. I did just realize that we didnt use plastic RAD in the race cars, we only used all metal ones....sorry about that

you have to use the kind thats for plastic not metal and you have to make sure that the area is very clean so clean it twice if you have to...best of luck

Yea that worked for us so many times and we never had to go back to fix the same hole twice....best of luck

Racing motors do not use antifreeze; a minor head warp or crack will allow antifreeze into the oiling system and destroy every bearing in the motor. That's kinda an important detail, because JBWeld and antifreeze do not like each other and once the antifreeze manages to push through to the JBWeld, it will begin the process of molecular deterioration, leading to failure.

FrankM29 I made this statement on the behalf of how we used to do it. I don't know where you come from but where I'm from this is how we did it. We we're not a big time outfit and we only raced on our local 1/4 mile track. On the chance that we did blow an engine the oiling system was of no use anyway because we had a very big hole in the side of the block. We ran using JB weld for more than 20 years and my Father and uncles ran using it for 40 yrs so we never had a problem with it coming apart and getting into the oil system. We did not have the big very expensive engines that it might do some harm too all we had was regular street engines beefed up a bit but nothing that expensive.

Sorry, I don't know if I sent this to the wrong person earlier. Was the JB Weld type regular or did you use Water Weld type?

We just used the regular for ours and we never had another problem with them. I know that this didnt work for some people on here but what it comes down too is getting the mix right. If you are useing the JB Weld on something that will be heated up and cooled down many many times the mix has to be right.

Good luck with your problem and I hope this helps.

i ran a radiator shop for three years an if a tank (plastic) was cracked we replaced it whether it was our own or a customers all attemps to repair plastic tanks could not hold up to the pressure of the system in operation motor cost way more to replace than plastic tank

Look these guys are in for the money. Epoxy is stronger then the plastic used to make your car. You can simply use Epoxy, I recommend JB marine wield $4 at a local store, to repair cracks, fissures, or even small holes. If plastic can withstand system pressure so can the jb weild. (which also bonds metal) These guys are in for the money. Think about how much they lose if everyone learned or even thought that you can attempt most repairs yourself without replacing the entire system. If they are replacing the same part who to say it won't break again due to design flaw in the same spot / area.These guys don't even know how plastic is made, nor the bonding strength, nor how epoxy works. They can't even prove why it doesn't work. It's a simple fix. Btw superglue does not work. I tried that in my testing first. I chose the marine wield because it's also liquid proof. Regular might work as well. These guys will just make it way more expensive for you so they can earn more. (Greedy as ****) Kinda makes me mad. Don't fall for it. Try this at lest once.

I had my leaky plastic radiator replaced with a new one at a radiator shop way out of town for around $400. After 6 months it started leaking at the seams and eventually wouldn't hold any fluid; after a temp silicone job it leaks again. Why would I want to put in another plastic radiator? is there an alternative?

After all the attempts to try and fix this one I ended up buying a new one on eBay for around $69 and it's still working after all these years and no leaks at all with this Neon. The glue I used back then never held up. Now for this other Neon I have the same problem and it's the same year as the other Neon. I did tried to plastic weld it using zip ties and a wood burner I already had. I did manage to seal it for a while but I it still leaked a little because when I did it I was in a hurry and I knew I didn't do a good job because the wood burner doesn't get as hot as a plastic welder does but I will try again with the proper tool when I get one. I did saw I new plastic welder video online where they used a similar plastic welder with a flat tip that look like a clothes iron but smaller to fix a radiator but the difference in the welder was that you feed the plastic sticks into a hole on the welders tip, where it heats it and melts the plastic strip at the same time while you are melting the plastic on the radiator surface. I think this method will work best because it's forcing the plastic into the crack while it's being melted mixing it all at the same time while doing the repair. Why they make plastic radiators?? Because it's cheap and they don't care if you have to replace it in ten years because by then it's not their problem but yours. You can probably find one all metal radiator that you can adopt to fit into a car but it will cost you and then you will have to spend more on other things to make it work then there's trying to locate one to make it fit. If it's a car you know you will keep for ever then it will be worth it but not too many people keep cars for very long anyways. Also if that radiator you got at the shop leaked only after 6 months then you still might have a warranty on it so I might look into that.

At least two of the posters above are wrong you CAN repair your own plastic radiator and save a ton of money doing it.All you need is a plastic welder and rods and a little patience.I repaired mine 6 months ago and still no sign of any leaks or cracks.

You can find full instructions with helpful pictures here http://www.urethanesupply.com/radiator.php

You can get by with the nylon zip ties and soldering iron as some have mentioned, but the proper tool is a lot easier to use for a smoother repair, and the whole kit from these guys is only $69.95 and it will also fix other things (like my minivan bumper cover) that are made of materials that melt. I can say that melting in some reinforcement like the fiberglass mesh is probably a good idea too, but it might end up weakening the repair if all air holes are not smoothly melted out.

Complete Instructions on How to Repair a Plastic Radiator 1. Step 1 Go to your local auto parts store or home center and purchase a tube of JB weld. Give them a call before you make the trip down there to avoid wasting your time. Get a large tube, just in case the crack is larger than you expected it to be. It is good to have more than you think you need. 2. Step 2 Drain the radiator of fluid enough to where if you push on the crack no fluid comes out. Locate the leak and dry the area as much as possible. Wipe it down with a shop rag and acetone (no soap), and examine how large the crack is. Once the area is dry use an extension cord and blow dryer on the crack. Push down on the crack to get in between the crack and dry. Again wipe down with acetone and clean. You need to make sure the area is clean. 3. Step 3 Use very rough sand paper to rough the area around crack. Use a sharp tool (Dremell with sharp sander is good) to score the plastic near the crack. Be careful that you do not put so much pressure on it that you make it worse, but enough to make some gouges in the plastic. This will give the JB Weld something to grip onto other than slippery plastic. Make a few deep scratches in the plastic. Make sure you rough an area about 3/4 inches all around the crack. Use a clean white damp cloth to wipe roughed area only (use one finger to wipe), check the cloth after wipe down if it is dirty then clean area again with acetone; repeat until after a damp wipe down the cloth is damp but clean. Use blow dryer again to thoroughly dry area. 4. Step 4 Get Painters Tape and tape around the 3/4 inch rough mark. You should have a rough square area with tape around it. This will be your patch area. The tape is to avoid making a mess especially if you are not removing the radiator. Get a piece of cardboard so you have a surface that can be thrown away after you mix the chemical on it. Mix the chemical with a stick or plastic fork. 5. Step 5 Generously apply the chemical with plastic knife to the area of the crack. If you can, squeeze the gap together and make sure that you have applied the chemical to the inside of the crack. Once you have covered the open crack make sure that you cover up the crack and any gaps or exposed cracks. Once you have applied this chemical, it helps to use your blow dryer again. It will harden rather quickly if you keep the heat directly on it for a minute or two. You need to apply enough material to cover the crack and the 3/4 inch area around the crack; and it must be about 1/8 inch thick. Make sure that as you apply the chemical some of the chemical may begin to run on to the tape, you need to bring this material back to the area between the tape. Repeat this until the chemical begins to thicken enough to a point that when it runs it is very very slow. At this point remove tape, and keep the chemical within the square. If you need to put more on after this go right ahead. But it is best if you have one solid piece rather than layers. The dimensions of your patch are very important due to the vibration, pressure, and heat generated by the radiator. If the dimensions and chemical used are smaller the patch will probably not last. 6. Step 6 Let the radiator with patch set for 24hrs, after 24hrs refill with radiator fluid, turn on car and run for 40 minutes idle. Keep an eye on radiator for leaks in and around patch area. You will probably smell radiator fluid and have some steam. This is probably radiator fluid that may be on the engine, but should be gone within 30minutes. If the patch hold with no leaks your good to go!!!

My experience is that JB weld and antifreeze don't mix. Actually they do but not in the way that one would like. There is some sort of chemical reaction that takes place that breaks down the JBweld. What would be more helpful to know (which is why I came to this forum) is what kind of plastic is used on radiators (are all brands the same?) and then determine what kind of glue repair would be appropriate.

While looking for plastic radiator repair info, I did find this link to a place that sells the welding tool that melts the plastic and the plastic filler sticks to thicken the weld and make it stronger.
These tools are also available at various other places, but the most important things on this site were the instructions. It makes sense that since the radiators expand and contract that any kind of glue is going to eventually fatigue and fall off, so melting the crack and welding it together does seem to be the only repair that will last. And if the repair is well done, there is no reason to think it won't last as long as the rest of the radiator.

Heres the link this guy copied from: http://www.ehow.com/how_4465034_fix-cracked-plastic-radiator.html

Madrasi, It sounds like you patched radiator with coolant still in it. Is this true? I have a 2007 sport trac, radiator is only about 2 1/2 yrs. old, seems to be structurally sound. There are 2 squares ( about 1" ) on each side of  bottom that looks like plugs from manufacturing process. Both are leaking anti-freeze coolant. probably almost impossible to clean this off without draining, but then it won't be hot as you say.  Think it will work with fluid. Ford dealer wants app. $800 to replace radiator. Haven't checked other prices right yet because that got my attention in a hurry.
Thanks to all you guys for great info. Just what I was looking for.

Sorry about the time delay but I have been down with a back injury but just for FYI to the question when we fixed the tanks with the JB weld the tank was empty do to the lose of the fluids during the race. by the time the race was over we lost most of the fluid in the tank do to the leak and high pressure in the tank. The main thing is that the tank has to be hot at min temp. up to operating temp or over. when the product is hot it expands and opens any hole in it and that's the best time to fix it, then when it cools down the hols will contract and close sealing the hole.
I can honestly say that this practice worked very well for us and saved us hundreds of dollars in repair money. I hope you got it fixed as cheep as possibale and got it back on the road.


6 years ago

Well you could try using mseal both inside as well on the outside let it dry not in the sun .......mine worked I do not have any leak from that area so far.The car is a 1999 E230 Mercedes Benz. if the leak is tiny use some leak stopper.

Open the crack and fill it with engine silicone evenly. Reinforce with a heat resistant epoxy. Since you have fiberglass cloth, it doesn't hurt to put some over the crack and epoxy it in place. Radiators aren't that expensive on breaker's yards.

You can't fix it. You can replace the cracked tank with a new one but that is just as expensive as buying a new radiator. The tanks are made from injection molded plastic and there isn't a product on the market that will vulcanize with it. Epoxy, glue gun, zip ties, and other things people have come up with here are temporary fixes (one or two days if you are lucky) because your radiator expands and contracts causing any substance you try and fix it with to crack loose as soon as you run the vehicle a few times. Also don't use stop leak as this will plug up everything but the leak. Sorry for the bad news. The best answer is to just keep adding water till you can afford to replace the radiator. www.intermountainradiator.com

Please visit  www.radiator3L.com  for radiator problem solutions.  Radiator brass tank replacement for leaking and cracked plastic tank.

 My crack in the plastic is at the top and closes when not very very hot.  Any ideas on how to seal it up?  Maybe groove it out then "weld" in some zip ties?

See below post for my leak. I grooved out area using a dremel grinder with a 3/32" router and patched it with a JB Weld product called Water Weld with coolant still in. Dried hard as a rock and hasn't leaked a drop in 5 days now.

ensure that the coolant level is well below the crack. Clean the crack with a small wire brush and acetone. When you are sure that the area is clean and dry, use a soldering iron to 'weld' a 'zip-tie' or tie-wrap into the crack.... it will take awhile, but continue applying heat to the tie as you press it into the crack (with the iron only - it will burn your skin!). Quality Tie-Wraps are made of the same basic plastics used in the radiator tank - so your weld should become part of the tank as opposed to 'sticking to' the tank. Adding JB weld over the area once you are certain that it is sealed will give structure to the area as pressure and heat are applied down the road!

how long would it take for the melted zip-tie to harden and the jb weld to dry right

NOTE: by plastics I should have noted Nylon Polyamide 6,6 (plus fillers etc)

i have a small crack in a plastic radiator. i called jb weld & asked their technical department would it work on a plastic radiator. without any hesitation they said it would not hold & they advised against trying it. my mechanic told me to use marine tex epoxy & make certain it is prepped well with acetone and rough sandpaper. however this procedure wasn't foolproof & if i wanted to gamble to keep an eye on the temp gauge.


JB Weld! this stuff is great and it will withstand high temps and when cured is probably stroner then the origninal material.

Actually I used that first and it didn't last a day. And I prep it good and let it dry overnight. = / . I was surprised I didn't work too.

Neons are known for this. If the plastic has cracked its probably weak every where. You could try 'glassing it but be prepared to buy a new one anyway. The used ones in the junkyard are probably just as bad but you may find a good one. There are some very good plastic specific two part adhesives out there too but if youve got glass why not try it?