Fixing a Cars Radiator





Introduction: Fixing a Cars Radiator

 Recently I got a crack in my radiator and found out its going to be $300 just to buy a new one, and thats If I installed it myself, it was going to be around $500-$600 to have someone do it for me, I looked into other ways and here's what I came up with. Total cost $16, time 15min. lasts forever.

Step 1: Materials

 I went to a local napa automotive store, and found a kit that is designed to fix cracks and holes in plastic parts on cars and containers. It's a fiberglass repair kit and only cost about $16. 

Step 2: Directions

 I followed the directions that came with the kit but there were a few things the directions said to do that didn't work as well as they claimed, I'll talk about what I found that happened or worked better in other parts as they come up.

The kit came with  a strip of fiberglass cloth,. sand paper, a metal tube 1 time use brush, and a 2 part epoxy.

Step 3: Other Tools

Some other tools you'll need is a few simple things.

1.Scissors for cutting the fiberglass cloth to correct shape.
2.some sort of tool to scrape off excess material during the cleaning process, I used a small pick, a screw driver would work just as well.
3.A drill and a drill bit, the drill and bit are used to ensure the crack doesn't spread, Ill explain all that in detail
4.  air filter mask, I used a simple painting mask, but any filter mask would be fine.

Step 4: Cut the Fiberglass

 Cutting the fiberglass is really easy. it is just like cutting normal fabric so normal scissors work fine.

Step 5: Preping the Area

Make sure you scrape all excess dirt, grease, or any other dirt off, and wipe clean with a cloth or a rag, don't use paper towels because the may leave traces of fibers behind. Then use the sand paper to sand anything off that is left behind, and in order to give the fiberglass a surface to stick to.

Step 6: Drilling the Holes

 Drill small holes at the end of each crack to ensure the crack doesn't spread any further, I followed the direction that came with the kit for these steps. It was fairly simple, I used a 1/8th in drill bit but depending on the size of the crack you can use whatever size you need, don't go too big, the hole just needs to stop the crack.  

After the holes are drilled make sure you sand the area around the holes again so the fiberglass sticks to the surface.

Step 7: Mixing the Epoxy

 The bag of the epoxy tells you to squeeze the black section at the bottom and break the center seal. I found that once the center seal is broken squeeze both ends and it opens the entire seal. Once the seal is broken the directions say to mix for 30 seconds then once you cut the corner you have 5 min to apply. The directions are wrong, once the 2 mixtures interact you have less than 5 min before it starts to harden.

once you cut the corner of the packet open, apply some using the supplied brush to the surface of the area on and around the crack. Then spread the fiberglass cloth over the cracked area and cover the cloth with the rest of the epoxy. 

After about a min the epoxy starts to heat up, it got to the point where I could barley hold it, it started feeling like it was going to burn my fingers.. Once it gets hot it started coming out of the packet even faster more like a liquid and then within 30 seconds started to harden coming out of the pack. so move quick. 

I'm sorry I don'y have pictures of me applying the epoxy, once it was mixed I have about 3 min to do it before it hardened.

Step 8: Done

once its done it said it hardens within about 20 min, I left it over night in case it wasn't ready. If you use it too soon and it leaks, it will be almost impossible to scrape off the previous fiberglass and do it over. you can lightly sand the surface if your worried about the looks. mine is on my radiator under the hood so I wasn't really worried about making it look good.



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49 Discussions

its a simple epoxy and fiberglass patch, as it may be working now, the time it lasts will depend on how clean it was when you applied said patch. I hat to be the bearer of bad news, but this is FAR from permanent. But dont trust me, Im just a pipe fitter who has temporarily repaired pipe (glycol lines) with far superior products in the oil field industry... the glycol, with heat and pressure will eventually cause a leak again..

1 reply

...That was really insightful contribution; thank you, Captain Obvious!

If there is just a crack on the plastic part of the radiator and no damage on the aluminum part,you can take tge radiator out and either replace the plastic tank or have a shop replace the plastic tank,its not hard to do and most shops,if you bring them the radiator, will fix it for probably less than 40-50 bucks.

I have been in the radiator repair business for 33+ years I own my own shop in southern California and I can tell you that won't work for a permanent repair. It may buy you some time a week or a month but it will not be permanent. I have seen hundreds of these attempted repairs with every glue you can imagine and nothing works.

1 reply

Just to be fair, you might not know if a lot of the repairs have worked and held. Working in a radiator shop, I doubt that people bring their radiator to you after it has already been fixed and isn't having any additional problems. Not that I think that the glue is a good idea, just think you might only see one side of it.

go to pick a part.. On the holidays in everything is half price.. You can get a good one of your choice. About $20.00 dollars


2 years ago

Radiators aren't made the way they used to be -- plastic and aluminum instead of brass and copper. They simply aren't easy to fix -- "patch" is a more correct term, as the repairs are pretty much temporary. The hot coolant mix and lots of thermal expansion/contraction, plus the coolant is under pressure (15-20 psi, most common in US is 16 psi) just don't lead to permanent repairs. The good thing is radiators are relatively cheap now, usually under $300 US. That's a good chunk of change if you are on a budget, but much less than replacing an otherwise good car. If on a budget you'd be better off to go to a salvage yard and find a radiator that will fit. Get one from the newest model that will fit (if you're handy you may be able to adapt from a much newer model). Even then it's a crap shoot -- the "new" radiator may not last more than a few weeks ( most salvage yards have a 30 day exchange warranty, some you have to pay a few bucks more to get that) or a year anyway. There's a lot of work involved in replacing the radiator, more than I'd want to do for a patch that may not last. I'd risk a salvage yard radiator first.

I've found a fairly simple solution to successfully repair a cracked plastic radiator.

Sand the crack and clean the area put some epoxy putty over it make sure it's placed on and pushed in correctly leave no spots for the coolant or air to leak out of and the trick is after its dried enough so it's hard rub water over it.

I've found a fairly simple solution to successfully repair a cracked plastic radiator.

Sand the crack and clean the area put some epoxy putty over it make sure it's placed on and pushed in correctly leave no spots for the coolant or air to leak out of and the trick is after its dried enough so it's hard rub water over it.

I think mine is leaking around the top of the neck. I'm going to try solar 900 caulk, it sticks to everything. It's crazy strong and clingy.

My son's car is having problems with its radiator. It has been given out in the past month. It's an older car, but other then that it has been working just fine. So I am wondering if it would be worth it to get it fixed or just to start looking for another car? <a href='' ></a>

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.

1 reply

I'm sorry your repair did not succeded.  Most Radiator tanks are made with Nylon 6-6 mixed with short fiberglass mixed in a 70-30% mix. Replacing the radiator with a new one is out of the question, as it goes AGAINST THE SPIRIT OF INSTRUCTABLES and the DIY BIBLE too...  We WANT to presume that we were successful in repairing almost anything!

THE secret for a successful repair, is based on getting several things properly done:
1) CLEANLINESS of the surface where the patch will be attached to.
2) REINFORCEMENT of the patch (that is why fiberglass mat is for).
3) Use of a GOOD resin to make the repair.  More below.
4) PROPER surface finish where the patch will be grabbing.
5) Application INSIDE the epoxy time window.

(1) Clean throughly. Sanding first is a must. The suggestion on using a strong cleaner ("Brake Cleaner") can be either a large help, or a failure point, depending on the TYPE of cleaner: nowadays there are TWO distint classes of Brake cleaners: Those containing Clorinated agents, and those based on Non clorinated solvents. Let´s ask the commenter that suggested its use to please tell us which one did he use. In any case, let the solvent evaporate at least 2 minutes to avoid trapping solvent that will weaken the epoxy.

(2), (3) and (5) For the fiberglass mat to provide a good mechanical resistance and attachment to the radiator material, it needs to be completely and throughly wetted with the epoxy. THEREFORE, you need to perfectly wet the textile with the epoxy, which means that a too viscous, paste like epoxy is NOT going to wet the fiberglass.  Thus, I may suggest that instead of using a "Patch Kit", why not go to a Model Airplane Hobby shop and purchase a finer weave Fiberglass Cloth and a much SLOWER epoxy resin, called "finishing resin", usually over two HOURS setting time. That will give you plenty of time to wet the cloth, get inside every microscopic ridge and channel onthe nylon tank, and level itself to give a nice appearance too.  Any epoxy faster than that wont give as good a result.

(4) A rough (but not too rough) surface is best. Try using 120 or 150 sanding paper (wet--or-dry type is better).
 Enough thickness is necessary to achieve the required strenght, this means two to three thin cloth layers (2 Oz per square yard cloth).  Even when the hobby shop cost of the Finishing resin and cloth will be higher than the NAPA (or similar) patch kit, it will produce a much better patching, that, when properly done will outlast the car.  Mt two cents.  Amclaussen, Mexico City.

P.D.: The suggestions about using "JB Weld" are not good, because JB Weld has metallic filings as reinforcement, but several layers of thin fiberglass cloth are a much better reinforcement, albeit a little slower and requiring more dexterity.  The reason the fiberglass cloth is much better, is that it has much higher tensile strenght AND it has a very similar thermal expansion behavior than the nylon tanks.  JB Weld does not perform as well.

Way to go. A word to the wise, a little spray of brake cleaner will soften the plastic up just a tad, giving the right epoxy a chemically tight bond. It will also remove any contaminants as well. I use brake cleaner on inner tubes when I patch them, to get all the junk off. It works...

Way to go. A word to the wise, a little spray of brake cleaner will soften the plastic up just a tad, giving the right epoxy a chemically tight bond. It will also remove any contaminants as well. I use brake cleaner on inner tubes when I patch them, to get all the junk off. It works...

i tried it with special liquid which you pour into the radiator and it closes the hole(s)
.. didn't help but  the hole was quite big

3 replies

 stop leak only works if you have a pin hole in the metal part of the radiator, for large holes and cracks you need to do something like this for the plastic parts or if it's metal use JB weld

Hi Vikking,
My radiator just sprung a pinhole leak and I was wondering how your repair has held up so far?

since the crack was so large, it lasted a little less than a year, the plastic kept separating, the process i showed is more for pinholes, i was just trying to save it until i got a new radiator. this process should work for pinholes with no problems, the problem i kept having it it kept pealing off, so make sure you scuff up the plastic and give it something to hold onto