Can you repair a broken plastic fitting on a radiator?

After having bad luck with a cheap aftermarket radiator that I purchased online from Rock Auto, I decided to order the official OEM part from a company in Korea. I ordered two of them to have a spare, and they arrived yesterday. Unfortunately, one arrived with a small plastic hose connection broken off. This hose connection goes from the top of the radiator on the driver’s side to the expansion tank, and functions as a bypass/return path. It mates with a 3/8" hose.

Since the radiator was fairly expensive, including the cost of shipping, I want to repair it. Some people online talk about using a so-called “plastic welder”, others talk about certain types of epoxy, and others talk about cutting off the jagged edge, drilling out and threading the hole, and screwing in a male thread to male hose connection adapter.

See pictures:

Let me know what ideas will work in order to salvage this. Obviously, I am installing the good radiator right now, so this is just to have a spare when needed.

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I’d tap it with a proper size pipe thread tap and screw in a barbed fitting with thread sealant.



Send it back.
Demand a refund on the unused radiator.
Contact you credit card company.
Radiators wear out so infrequently that you don’t need a spare.


Have you tried to file a damage claim with the shipping company?

see if company will pay return shipping. a lot of companies will.

Yeah, why fix it? Just return it, get one you can trust.

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Tapping will probably work, glueing or plastic welding definately won’t but returnng for a replacement makes the most sense.


As above, contact the supplier, tell them that one was received damaged. Request refund and they pay for return shipping. Who knows, they may even refund the cost and allow you to keep it!


I’m with the drill, tap, and screw in a brass fitting camp if you can’t return it.

What were the issues you had with the RockAuto radiator and what brand was it so we’ll know to avoid that brand in the future? I have bought new ones that seeped coolant when new at the plastic end tank joints. It’s been a few years, so I don’t recall the brand.

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I forget the brand of the Rock Auto radiator. None of the brands which Rock Auto offers for this car are brands which I have ever heard of. Usually, I have good luck with parts from Rock Auto, and have saved some serious money there.

I installed the radiator last year, and put less than 1800 miles on the car since completing the engine repairs. I started noticing that the coolant in the overflow tank was dropping, which I topped off, but did not see an obvious leak.

Eventually, I stopped at a grocery store, and when I came out, I observed coolant dripping from the frame rail under the radiator onto the ground. I had assumed the leak was a hairline crack in the finned part of the coil, but it was actually the crimped connection on the side.

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Is this the suggested fitting to use, 3/8" hose barb to 1/8" male NPT? And just file down the rough edge and use a standard 1/8" NPT tap?

You want to drill out the hole with a 13/32 drill bit,

This is a slightly smaller hole than required for hard materials such as metal.

When tapping the hole, apply grease to the tap flutes to catch the plastic chips.

And don’t forget to back the tap off every 1/4 turn to break the chips off.


That seems to be where the aluminum radiators always fail (the crimp at the plastic end tanks). I’ve never seen one fail anywhere else, unless it was punctured.

After drilling a large hole in the radiator, you won’t be able to make a shipping damage claim.

This is how my radiator was delivered, they could have made an effort to keep the radiator in the box and place it on the sidewalk, fortunately there was no damage.

I fixed a nub by inserting some brass thin wall tubing inside to reinforce it. You could flare one end and use a bit of sealer on the flared part. Or, get a refund.