What causes radiator leaks

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I have an 07 4Runner v6 130k miles with what appears to be a radiator leak. I changed the coolant at 100k per Toyota recommendation. It's gonna cost roughly 350-400 dollars to replace. What causes radiators to leak in the first place?
 
I would assume heating up and cooling down over and over and over....
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Not to mention all the bumps the car has to go through and the exterior can also be damaged from road debris, corrosive chemicals, rust, etc.
 
A Denso radiator from RA is $96... $125 with shipping and tax.
The ol' switcheroo could easily be completed in an afternoon...

And as for what causes it to leak, we are talking about a 12 year old vehicle here with 130k+ on the clock. There's 127 reasons why it's started to leak now.



Screenshot_2019-05-20-20-17-47.png
 
Galvanic corrosion, Electrolysis, Age, stresses, coolant interacting with materials,
rocks, animals, careless mechanics.
What did I miss?
 
Older automotive radiators were usually made of aluminum alloy or copper alloy. Alloys have impurities and those impurities cause weak spots that are vulnerable to corrosion. Eventually, a pin-hole forms. Also, the seams are either brazed, soldered or tig welded. All three of those bonding methods introduce vulnerabilities and imperfections which eventually give-way over time after many heat/cool cycles. Same goes for modern radiators that are plastic with bonded cooling tubes.


Ray
 
In addition to what's been said, don't overlook manufacturing defects. Had one radiator fail because the tanks were crimped OK, but was not soldered well so the seam let go. Also had the plastic tank on my Saturn fail because of a weak spot that eventually bulged out and cracked. The radiator on my MG failed because the PO must have had some very dilute antifreeze that froze and cracked the lower tubes. Corrosion may have helped that one, but the heater core also had burst seam.
 
What causes most radiator leaks is that most radiators are manufactured with plastic end caps crimped to aluminum cores
Doesn't work well over time
 
the "glued" on cheap high temperature nylon end tanks are often an issue as the girlfriends 5 year old 55 thou malibu, then the cheap GM water pump leaked next!
 
Last edited:
Originally Posted by PlzRepond
I have an 07 4Runner v6 130k miles with what appears to be a radiator leak. I changed the coolant at 100k per Toyota recommendation. It's gonna cost roughly 350-400 dollars to replace. What causes radiators to leak in the first place?


How many years old was the coolant when you changed it?

Did you test the coolant pH before you changed it?

What type / brand of coolant are you now using?

Take a look at: https://bit.ly/2XqXdly and https://bit.ly/2IMQ3UD

Ed
 
Originally Posted by Imp4

And as for what causes it to leak, we are talking about a 12 year old vehicle here with 130k+ on the clock. There's 127 reasons why it's started to leak now.


Interesting that the plastic top radiators in every older German vehicle Ive owned (81, 82, 83, 85, 2x91) have all been original, a number of them having >>200k on top of the decades old age.

Meanwhile, the radiator on my parents 94 Previa was the only thing that failed more than once on that van, which was super reliable and great until Hurricane Sandy caused its demise with >230k.

I think I'd argue Toyota (and Honda, personally encountered two integrals with hairline cracks in the radiator tops) don't make their radiators thick or robust enough.
 
Not sure how a plastic tank can crack from failing to change coolant. I think for these type they just outgas over time, and eventually get brittle, and then crack. On all metal ones though I can see how galvanic reaction will take something out.

Happened to notice my '99 with a crack a couple weekends ago. Thankfully it was not only cheap but quick & easy. On a 4Runner I'd be quick to change as on those they are known to mix coolant and ATF, and that's a great way to kill the trans. I'm not sure the failure mode is related to coolant change frequency.

It's mechanical, everything mechanical breaks. Just like everything electrical, and everything relational, and ...
 
I was more curious to find out if things like a faulty thermostat or bad radiator cap could have failed and maybe built up extra pressure/temp in the radiator and caused it to crack/leak?
 
Originally Posted by PlzRepond
I was more curious to find out if things like a faulty thermostat or bad radiator cap could have failed and maybe built up extra pressure/temp in the radiator and caused it to crack/leak?


That's entirely possible, and happens on older cars a slight leak in head gasket can build up just enough extra pressure in the system and promote a more rapid failure in plastic tanks. That being said if this is a cause you SHOULD see some bubbles in the fluid while the engine is running.
 
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Originally Posted by PlzRepond
I was more curious to find out if things like a faulty thermostat or bad radiator cap could have failed and maybe built up extra pressure/temp in the radiator and caused it to crack/leak?


A bad radiator cap would leak and thereby lower your boiling point dramatically. I think it's 2 degrees F for every one psi, so a 15psi cap would add 30 degrees to your water/coolant boiling point.

A thermostat is just a temperature sensitive gate. If it fails open, you're just cycling coolant non stop and that won't build up pressure in your radiator. If it fails closed, it means you're circulating coolant through the radiator only (and not the block) and you should have noticed high temps if that happened.

In the 30k miles you drove between the new leak and last coolant change, you would almost certainly have noticed a bad radiator cap due to boil over.

What "caused" YOUR leak? Dunno... ultimately it's either physical/mechanical failure or chemical like corrosion. Unless you're willing to do an autopsy on your radiator, you'll never know for certain what killed it. And because everyone's driving habits, terrain and adherence to maintenance etc is different - there's no "usual" culprit. For some it'll be a mechanical failure like a crack, for others that haven't been good about changing out the coolant regularly it's most likely gonna be corrosion.
 
Last edited:
Originally Posted by PlzRepond
I have an 07 4Runner v6 130k miles with what appears to be a radiator leak. I changed the coolant at 100k per Toyota recommendation. It's gonna cost roughly 350-400 dollars to replace. What causes radiators to leak in the first place?

Expansion & contraction, neglect.
 
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