I have a radiator in my truck that has a slow leak which looks like it is oozing a little bit in between some of the fins. What are some of the ways to repair a radiator without replacing it? At what point should it just be replaced completely?

I have seem the little additive bottles that claim to fix small leaks. Is this the only option?

3 Answers 3


I wouldn't use additives to plug a leak unless it's an emergency. That stuff migrates all through your cooling system gunking up everything it can in the process - including radiator tubes with a partial flow restriction...

If you are fortunate enough to possess a brass radiator - take it to a rad shop to have the leak soldered. At the same time, get it boiled/rodded out since you've already taken the time to remove it anyway.

However if it's a modern radiator w/ plastic end tanks and aluminum core, your best bet is just to buy a new replacement. Most of those style radiators are relatively inexpensive in the aftermarket, I replaced one in my 93 Honda Accord about 6 years ago and I think it was 80 dollars at the time. I think the old aluminum might have some salvage value at the scrap yard...

Think about it this way - is saving 200 bucks on a radiator repair really worth the cost of an overheating related blown headgasket or worse? Previous owner of my motorhome overheated the rig so bad once it cracked the heads in addition to melting down the transmission. So yeah, going cheap on the cooling system can have painfully consequential effects down the road.


It's likely non-repairable, unless the vehicle is 15 years + old. The new style radiators are not cost effective to repair. A leak between the tank and the core, can usually be repaired, a leaking tank can usually be replaced. Core repair is difficult if possible, they are made so thin now it's next to impossible to repair.

Check with a radiator repair shop and compare the price and warranty of new vs repair. Unless there is a big savings 25% or more I would go with the new one.

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    It's worth mentioning that with the newer radiators sometimes the problem is nothing more than the o-ring that seals the tank to the core, which is a cheap fix. Mar 8, 2011 at 2:24

First up, after about 4 decades of trying different things I'm absolutely convinced that the only worthwhile solution is to take it to a radiator specialist and see what they can do with it. Personally, every time I've tried one of those leak sealing compounds I always end up feeling like I've been ripped off. At best they only work for a very short time.

In an emergency situation, such as when you're camping a long way from anywhere, and provided the leak is pretty small, you can put an egg white (only the white) into a radiator that is already up to temperature. Don't laugh, this really works.

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    This is supposed to be a site for experts. Answering a question with "take it to an expert" is not a great answer on a site that's supposed to be for experts... if you don't have a great answer, wait for someone who does. Mar 8, 2011 at 4:10
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    @Joel, sometimes the best advise that can be given is to not even try. Few people outside the radiator industry have the facilities to do such work and merely cause more damage in the attempt. However, if you feel the answer is sub-standard just delete it. Mar 8, 2011 at 4:35
  • @Joel, John's advice was not "take it to an expert" but take it to a specialist. And someone asking about the "little additive bottles" probably should consider this advice. The advice I've heard over the years is similar, but I've done very little work with radiators. Mar 8, 2011 at 9:07
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    fair enough, I apologize for that. I'm just being overly sensitive during the beta to make sure this site stays pro-level, and I overreacted in this case. Mar 8, 2011 at 16:43

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