Do I need to flush the coolant when replacing a cracked radiator?
When a radiator is cracked, people worry that pressurized coolant might mix with the engine oil during a flush or while running the engine. This fear makes it difficult to decide whether to perform a system flush with the old radiator or simply install the new one and let it ride.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1Testing the coolant condition to see if it is still good before deciding
- 2Replacing the radiator and installing fresh coolant without performing a full system flush
- 3Removing the radiator and thermostat to flush the system with a hose before refilling
- 4Skipping the flush unless there is a specific reason to believe the engine has a sludge issue.
In their words
Unedited, most upvoted first, each linked to the thread it came from.
“I did test it and it is still good it's just I'm afraid of the pressurized coolant mixing with the engine oil through that crack in the radiator.”source ↗
“I get that they are separated but I'm concerned it's no longer separated because of the cracks and I'm more worried about that pressurized coolant pushing past a crack if it goes deep enough and mixing with the oil that's going to the engine.”source ↗
Where this came up
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