I have a cracked radiator that I plan to fix or replace. I am concerned, though. I did some rudimentary Google research and the general consensus is that I may potentially be replacing parts without diagnosing the actual failure.

Some of what I read suggested that a head gasket failure can cause excessive pressure in the radiator. That perplexed me because my understanding of the cooling system is that is intended to release overpressure into the reservoir.

So here's my question: How can a head gasket failure cause a radiaor to crack from pressure if it's designed to release pressure in the reservior?

  • How old is the vehicle, and what mileage has it covered? Are there any other relevant symptoms (oil in the coolant, excessive pressure in the radiator, unusual smoke coming from the exhaust)? Jun 13 '20 at 15:56

That depends what material on the radiator cracked.

If it was metal (brass or aluminum) then it could be due to fatigue and can happen on the top or bottom hose to header tank joint.

If the material is plastic then there may have been a fault in the plastic or it has been hit at some point which can cause it to weaken over time.

If the pressure cap is functioning correctly then even if the head hasket is leaking the excess pressure will be bled off.

  • Plastic end caps are a poor material choice for a radiator , not strong enough. That i why the plastic in my Titan failed. Plastic can be made strong enough , but that is not what the "low bidder" offers to the auto manufacturer.Don't over think it. Jun 13 '20 at 14:30

The radiator is designed to cool the coolant, not regulate any pressure. The radiator cap applies a set pressure that allows coolant pressure to be relieved into the over flow tank, and also intake addition coolant if needed.

I have not seen, in my professional automotive career, a head gasket cause a radiator to crack. You would need to verify your head gasket concern with a carbon detector, and any leaks with a pressure tester.

Plastic sides have been used for years, literally 30 years or more on radiators.

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